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Boyer M, Baudin P, Stengel C, Valero-Cabré A, Lohof AM, Charpier S, Sherrard RM, Mahon S. In vivo low-intensity magnetic pulses durably alter neocortical neuron excitability and spontaneous activity. J Physiol 2022; 600:4019-4037. [PMID: 35899578 DOI: 10.1113/jp283244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 07/21/2022] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Repetitive transcranial magnetic stimulation (rTMS) is a promising technique to alleviate neurological and psychiatric disorders caused by alterations in cortical activity. Our knowledge of the cellular mechanisms underlying rTMS-based therapies remains limited. We combined in vivo focal application of low-intensity rTMS (LI-rTMS) to the rat somatosensory cortex with intracellular recordings of subjacent pyramidal neurons to characterize the effects of weak magnetic fields at single cell level. Ten minutes of LI-rTMS delivered at 10 Hz reliably evoked action potentials in cortical neurons during the stimulation period, and induced durable attenuation of their intrinsic excitability, synaptic activity, and spontaneous firing. These results help us better understand the mechanisms of weak magnetic stimulation and should allow optimizing the effectiveness of stimulation protocols for clinical use. ABSTRACT Magnetic brain stimulation is a promising treatment for neurological and psychiatric disorders. However, a better understanding of its effects at the individual neuron level is essential to improve its clinical application. We combined focal low-intensity repetitive transcranial magnetic stimulation (LI-rTMS) to the rat somatosensory cortex with intracellular recordings of subjacent pyramidal neurons in vivo. Continuous 10 Hz LI-rTMS reliably evoked firing at ∼4-5 Hz during the stimulation period and induced durable attenuation of synaptic activity and spontaneous firing in cortical neurons, through membrane hyperpolarization and a reduced intrinsic excitability. However, inducing firing in individual neurons by repeated intracellular current injection did not reproduce LI-rTMS effects on neuronal properties. These data provide novel understanding of mechanisms underlying magnetic brain stimulation showing that, in addition to inducing biochemical plasticity, even weak magnetic fields can activate neurons and enduringly modulate their excitability. Abstract figure legend We examined by means of in vivo intracellular recordings in the rodent the effects of low-intensity (10 mT) repetitive transcranial magnetic stimulation (LI-rTMS) on the functional properties of primary somatosensory cortex pyramidal neurons. After a baseline period, during which cortical spontaneous activity and excitability were measured (Pre), LI-rTMS was applied at 10 Hz for 10 minutes. Despite their low intensity, magnetic pulses reliably evoked action potentials in cortical neurons. Ten minutes of LI-rTMS induced a progressive and long-lasting hyperpolarization of the neuronal membrane and a marked decrease in cell firing rate (Post). This was associated with an altered intrinsic neuronal excitability, characterized by reduced membrane input resistance and increased minimal current required to induce neuronal firing. A portion of this figure was created with biorender.com. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Manon Boyer
- IBPS-B2A, UMR 8256 Biological Adaptation and Ageing, Sorbonne Université & CNRS, Paris, 75005, France.,Paris Brain Institute-ICM, INSERM, CNRS, APHP, Pitié-Salpêtrière Hospital, team 'Network Dynamics and cellular excitability', Sorbonne Université, Paris, France, 75013
| | - Paul Baudin
- Paris Brain Institute-ICM, INSERM, CNRS, APHP, Pitié-Salpêtrière Hospital, team 'Network Dynamics and cellular excitability', Sorbonne Université, Paris, France, 75013
| | - Chloé Stengel
- Paris Brain Institute-ICM, INSERM, CNRS, Pitié-Salpêtrière Hospital, team Cerebral Dynamics, Plasticity and Rehabilitation Group, FRONTLAB team, Sorbonne Université, Paris, 75013, France
| | - Antoni Valero-Cabré
- Paris Brain Institute-ICM, INSERM, CNRS, Pitié-Salpêtrière Hospital, team Cerebral Dynamics, Plasticity and Rehabilitation Group, FRONTLAB team, Sorbonne Université, Paris, 75013, France
| | - Ann M Lohof
- IBPS-B2A, UMR 8256 Biological Adaptation and Ageing, Sorbonne Université & CNRS, Paris, 75005, France
| | - Stéphane Charpier
- Paris Brain Institute-ICM, INSERM, CNRS, APHP, Pitié-Salpêtrière Hospital, team 'Network Dynamics and cellular excitability', Sorbonne Université, Paris, France, 75013
| | - Rachel M Sherrard
- IBPS-B2A, UMR 8256 Biological Adaptation and Ageing, Sorbonne Université & CNRS, Paris, 75005, France
| | - Séverine Mahon
- Paris Brain Institute-ICM, INSERM, CNRS, APHP, Pitié-Salpêtrière Hospital, team 'Network Dynamics and cellular excitability', Sorbonne Université, Paris, France, 75013
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Nicotinic Receptor Subunit Distribution in Auditory Cortex: Impact of Aging on Receptor Number and Function. J Neurosci 2020; 40:5724-5739. [PMID: 32541068 DOI: 10.1523/jneurosci.0093-20.2020] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 05/11/2020] [Accepted: 05/27/2020] [Indexed: 01/08/2023] Open
Abstract
The presence of novel or degraded communication sounds likely results in activation of basal forebrain cholinergic neurons increasing release of ACh onto presynaptic and postsynaptic nAChRs in primary auditory cortex (A1). nAChR subtypes include high-affinity heteromeric nAChRs commonly composed of α4 and β2 subunits and low-affinity homomeric nAChRs composed of α7 subunits. In young male FBN rats, we detail the following: (1) the distribution/expression of nAChR subunit transcripts in excitatory (VGluT1) and inhibitory (VGAT) neurons across A1 layers; (2) heteromeric nAChR binding across A1 layers; and (3) nAChR excitability in A1 layer (L) 5 cells. In aged rats, we detailed the impact of aging on A1 nAChR subunit expression across layers, heteromeric nAChR receptor binding, and nAChR excitability of A1 L5 cells. A majority of A1 cells coexpressed transcripts for β2 and α4 with or without α7, while dispersed subpopulations expressed β2 and α7 or α7 alone. nAChR subunit transcripts were expressed in young excitatory and inhibitory neurons across L2-L6. Transcript abundance varied across layers, and was highest for β2 and α4. Significant age-related decreases in nAChR subunit transcript expression (message) and receptor binding (protein) were observed in L2-6, most pronounced in infragranular layers. In vitro patch-clamp recordings from L5B pyramidal output neurons showed age-related nAChR subunit-selective reductions in postsynaptic responses to ACh. Age-related losses of nAChR subunits likely impact ways in which A1 neurons respond to ACh release. While the elderly require additional resources to disambiguate degraded speech codes, resources mediated by nAChRs may be compromised with aging.SIGNIFICANCE STATEMENT When attention is required, cholinergic basal forebrain neurons may trigger increased release of ACh onto auditory neurons in primary auditory cortex (A1). Laminar and phenotypic differences in neuronal nAChR expression determine ways in which A1 neurons respond to release of ACh in challenging acoustic environments. This study detailed the distribution and expression of nAChR subunit transcript and protein across A1 layers in young and aged rats. Results showed a differential distribution of nAChR subunits across A1 layers. Age-related decreases in transcript/protein expression were reflected in age-related subunit specific functional loss of nAChR signaling to ACh application in A1 layer 5. Together, these findings could reflect the age-related decline in selective attention observed in the elderly.
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Parr T, Friston KJ. The Anatomy of Inference: Generative Models and Brain Structure. Front Comput Neurosci 2018; 12:90. [PMID: 30483088 PMCID: PMC6243103 DOI: 10.3389/fncom.2018.00090] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 10/25/2018] [Indexed: 01/02/2023] Open
Abstract
To infer the causes of its sensations, the brain must call on a generative (predictive) model. This necessitates passing local messages between populations of neurons to update beliefs about hidden variables in the world beyond its sensory samples. It also entails inferences about how we will act. Active inference is a principled framework that frames perception and action as approximate Bayesian inference. This has been successful in accounting for a wide range of physiological and behavioral phenomena. Recently, a process theory has emerged that attempts to relate inferences to their neurobiological substrates. In this paper, we review and develop the anatomical aspects of this process theory. We argue that the form of the generative models required for inference constrains the way in which brain regions connect to one another. Specifically, neuronal populations representing beliefs about a variable must receive input from populations representing the Markov blanket of that variable. We illustrate this idea in four different domains: perception, planning, attention, and movement. In doing so, we attempt to show how appealing to generative models enables us to account for anatomical brain architectures. Ultimately, committing to an anatomical theory of inference ensures we can form empirical hypotheses that can be tested using neuroimaging, neuropsychological, and electrophysiological experiments.
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Affiliation(s)
- Thomas Parr
- Wellcome Centre for Human Neuroimaging, Institute of Neurology, University College London, London, United Kingdom
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Parr T, Benrimoh DA, Vincent P, Friston KJ. Precision and False Perceptual Inference. Front Integr Neurosci 2018; 12:39. [PMID: 30294264 PMCID: PMC6158318 DOI: 10.3389/fnint.2018.00039] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 08/30/2018] [Indexed: 12/24/2022] Open
Abstract
Accurate perceptual inference fundamentally depends upon accurate beliefs about the reliability of sensory data. In this paper, we describe a Bayes optimal and biologically plausible scheme that refines these beliefs through a gradient descent on variational free energy. To illustrate this, we simulate belief updating during visual foraging and show that changes in estimated sensory precision (i.e., confidence in visual data) are highly sensitive to prior beliefs about the contents of a visual scene. In brief, confident prior beliefs induce an increase in estimated precision when consistent with sensory evidence, but a decrease when they conflict. Prior beliefs held with low confidence are rapidly updated to posterior beliefs, determined by sensory data. These induce much smaller changes in beliefs about sensory precision. We argue that pathologies of scene construction may be due to abnormal priors, and show that these can induce a reduction in estimated sensory precision. Having previously associated this precision with cholinergic signaling, we note that several neurodegenerative conditions are associated with visual disturbances and cholinergic deficits; notably, the synucleinopathies. On relating the message passing in our model to the functional anatomy of the ventral visual stream, we find that simulated neuronal loss in temporal lobe regions induces confident, inaccurate, empirical prior beliefs at lower levels in the visual hierarchy. This provides a plausible, if speculative, computational mechanism for the loss of cholinergic signaling and the visual disturbances associated with temporal lobe Lewy body pathology. This may be seen as an illustration of the sorts of hypotheses that may be expressed within this computational framework.
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Affiliation(s)
- Thomas Parr
- Institute of Neurology, Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom
| | - David A Benrimoh
- Institute of Neurology, Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom
| | - Peter Vincent
- Institute of Neurology, Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom
| | - Karl J Friston
- Institute of Neurology, Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom
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Parr T, Friston KJ. Uncertainty, epistemics and active inference. J R Soc Interface 2018; 14:rsif.2017.0376. [PMID: 29167370 PMCID: PMC5721148 DOI: 10.1098/rsif.2017.0376] [Citation(s) in RCA: 122] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 10/27/2017] [Indexed: 11/28/2022] Open
Abstract
Biological systems—like ourselves—are constantly faced with uncertainty. Despite noisy sensory data, and volatile environments, creatures appear to actively maintain their integrity. To account for this remarkable ability to make optimal decisions in the face of a capricious world, we propose a generative model that represents the beliefs an agent might possess about their own uncertainty. By simulating a noisy and volatile environment, we demonstrate how uncertainty influences optimal epistemic (visual) foraging. In our simulations, saccades were deployed less frequently to regions with a lower sensory precision, while a greater volatility led to a shorter inhibition of return. These simulations illustrate a principled explanation for some cardinal aspects of visual foraging—and allow us to propose a correspondence between the representation of uncertainty and ascending neuromodulatory systems, complementing that suggested by Yu & Dayan (Yu & Dayan 2005 Neuron46, 681–692. (doi:10.1016/j.neuron.2005.04.026)).
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Affiliation(s)
- Thomas Parr
- Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, 12 Queen Square, London WC1N 3BG, UK
| | - Karl J Friston
- Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, 12 Queen Square, London WC1N 3BG, UK
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Depaulis A, David O, Charpier S. The genetic absence epilepsy rat from Strasbourg as a model to decipher the neuronal and network mechanisms of generalized idiopathic epilepsies. J Neurosci Methods 2015; 260:159-74. [PMID: 26068173 DOI: 10.1016/j.jneumeth.2015.05.022] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 05/28/2015] [Accepted: 05/28/2015] [Indexed: 12/31/2022]
Abstract
First characterized in 1982, the genetic absence epilepsy rat from Strasbourg (GAERS) has emerged as an animal model highly reminiscent of a specific form of idiopathic generalized epilepsy. Both its electrophysiological (spike-and-wave discharges) and behavioral (behavioral arrest) features fit well with those observed in human patients with typical absence epilepsy and required by clinicians for diagnostic purposes. In addition, its sensitivity to antiepileptic drugs closely matches what has been described in the clinic, making this model one of the most predictive. Here, we report how the GAERS, thanks to its spontaneous, highly recurrent and easily recognizable seizures on electroencephalographic recordings, allows to address several key-questions about the pathophysiology and genetics of absence epilepsy. In particular, it offers the unique possibility to explore simultaneously the neural circuits involved in the generation of seizures at different levels of integration, using multiscale methodologies, from intracellular recording to functional magnetic resonance imaging. In addition, it has recently allowed to perform proofs of concept for innovative therapeutic strategies such as responsive deep brain stimulation or synchrotron-generated irradiation based radiosurgery.
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Affiliation(s)
- Antoine Depaulis
- Inserm, U836, F-38000 Grenoble, France; Univ. Grenoble Alpes, Grenoble Institut des Neurosciences, F-38000 Grenoble, France; CHU de Grenoble, Hôpital Michallon, F-38000 Grenoble, France.
| | - Olivier David
- Inserm, U836, F-38000 Grenoble, France; Univ. Grenoble Alpes, Grenoble Institut des Neurosciences, F-38000 Grenoble, France
| | - Stéphane Charpier
- Brain and Spine Institute, Pitié-Salpêtrière Hospital, Paris, France; Pierre and Marie Curie University, Paris, France
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Rowe DL, Hermens DF. Attention-deficit/hyperactivity disorder: neurophysiology, information processing, arousal and drug development. Expert Rev Neurother 2014; 6:1721-34. [PMID: 17144785 DOI: 10.1586/14737175.6.11.1721] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In this review, we draw on literature from both animal and human neurophysiological studies to consider the neurochemical mechanisms underlying attention-deficit/ hyperactivity disorder (ADHD). Psychophysiological and neuropsychological research is used to propose possible etiological endophenotypes of ADHD. These are conceptualized as patients with distinct cortical-arousal, information-processing or maturational abnormalities, or a combination thereof, and how the endophenotypes can be used to help drug development and optimize treatment and management. To illustrate, the paper focuses on neuro- and psychophysiological evidence that suggests cholinergic mechanisms may underlie specific information-processing abnormalities that occur in ADHD. The clinical implications for a cholinergic hypothesis of ADHD are considered, along with its possible implications for treatment and pharmacological development.
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Affiliation(s)
- Donald L Rowe
- The Brain Dynamics Centre and Department of Psychological Medicine, Westmead Hospital and University of Sydney, NSW, Australia.
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Bhattacharyya A, Bießmann F, Veit J, Kretz R, Rainer G. Functional and laminar dissociations between muscarinic and nicotinic cholinergic neuromodulation in the tree shrew primary visual cortex. Eur J Neurosci 2012; 35:1270-80. [PMID: 22487086 DOI: 10.1111/j.1460-9568.2012.08052.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Acetylcholine is an important neuromodulator involved in cognitive function. The impact of cholinergic neuromodulation on computations within the cortical microcircuit is not well understood. Here we investigate the effects of layer-specific cholinergic drug application in the tree shrew primary visual cortex during visual stimulation with drifting grating stimuli of varying contrast and orientation. We describe differences between muscarinic and nicotinic cholinergic effects in terms of both the layer of cortex and the attribute of visual representation. Nicotinic receptor activation enhanced the contrast response in the granular input layer of the cortex, while tending to reduce neural selectivity for orientation across all cortical layers. Muscarinic activation modestly enhanced the contrast response across cortical layers, and tended to improve orientation tuning. This resulted in highest orientation selectivity in the supra- and infragranular layers, where orientation selectivity was already greatest in the absence of pharmacological stimulation. Our results indicate that laminar position plays a crucial part in functional consequences of cholinergic stimulation, consistent with the differential distribution of cholinergic receptors. Nicotinic receptors function to enhance sensory representations arriving in the cortex, whereas muscarinic receptors act to boost the cortical computation of orientation tuning. Our findings suggest close homology between cholinergic mechanisms in tree shrew and primate visual cortices.
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Affiliation(s)
- Anwesha Bhattacharyya
- Visual Cognition Laboratory, Department of Medicine, University of Fribourg, Chemin du Musée 5, CH-1700 Fribourg, Switzerland
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Metherate R. Functional connectivity and cholinergic modulation in auditory cortex. Neurosci Biobehav Rev 2010; 35:2058-63. [PMID: 21144860 DOI: 10.1016/j.neubiorev.2010.11.010] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2010] [Revised: 11/08/2010] [Accepted: 11/26/2010] [Indexed: 11/26/2022]
Abstract
Although it is known that primary auditory cortex (A1) contributes to the processing and perception of sound, its precise functions and the underlying mechanisms are not well understood. Recent studies point to a remarkably broad spectral range of largely subthreshold inputs to individual neurons in A1--seemingly encompassing, in some cases, the entire audible spectrum--as evidence for potential, and potentially unique, cortical functions. We have proposed a general mechanism for spectral integration by which information converges on neurons in A1 via a combination of thalamocortical pathways and intracortical long-distance, "horizontal", pathways. Here, this proposal is briefly reviewed and updated with results from multiple laboratories. Since spectral integration in A1 is dynamically regulated, we also show how one regulatory mechanism--modulation by the neurotransmitter acetylcholine (ACh)--could act within the hypothesized framework to alter integration in single neurons. The results of these studies promote a cellular understanding of information processing in A1.
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Affiliation(s)
- Raju Metherate
- Department of Neurobiology and Behavior, Center for Hearing Research, University of California-Irvine, CA 92697-4550, United States.
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10
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Abstract
Sensory cortical neurons are highly sensitive to brain state, with many neurons showing changes in spatial and/or temporal response properties and some neurons becoming virtually unresponsive when subjects are not alert. Although some of these changes are undoubtedly attributable to state-related filtering at the thalamic level, another likely source of such effects is the thalamocortical (TC) synapse, where activation of nicotinic receptors on TC terminals have been shown to enhance synaptic transmission in vitro. However, monosynaptic TC synaptic transmission has not been directly examined during different states of alertness. Here, in awake rabbits that shifted between alert and non-alert EEG states, we examined the monosynaptic TC responses and short-term synaptic dynamics generated by spontaneous impulses of single visual and somatosensory TC neurons. We did this using spike-triggered current source-density analysis, an approach that enables assessment of monosynaptic extracellular currents generated in different cortical layers by impulses of single TC afferents. Spontaneous firing rates of TC neurons were higher, and burst rates were much lower in the alert state. However, we found no state-related changes in the amplitude of monosynaptic TC responses when TC spikes with similar preceding interspike interval were compared. Moreover, the relationship between the preceding interspike interval of the TC spike and postsynaptic response amplitude was not influenced by state. These data indicate that TC synaptic transmission and dynamics are highly conserved across different states of alertness and that observed state-related changes in receptive field properties that occur at the cortical level result from other mechanisms.
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Afarinesh MR, Sheibani V, Arabzadeh S, Shamsizadeh A. Effect of chronic morphine exposure on response properties of rat barrel cortex neurons. Addict Biol 2008; 13:31-9. [PMID: 18201293 DOI: 10.1111/j.1369-1600.2007.00087.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chronic exposure to morphine can impair performance in tasks which need sensory processing. Using single unit recordings we investigate the effect of chronic morphine exposure on the firing properties of neurons in layers IV and V of the whisker-related area of rat primary somatosensory cortex. In urethane-anesthetized animals, neuronal activity was recorded in response to principal and adjacent whisker deflections either stimulated independently or in a conditioning test paradigm. A condition test ratio (CTR) was calculated for assessing the inhibitory receptive field. In layer IV, chronic morphine treatment did not change the spontaneous discharge activity. On responses to principal and adjacent whisker deflections did not show any significant changes following chronic morphine exposure. The magnitude Off responses to adjacent whisker deflection decreased while its response latency increased. In addition, there was a significant increase in the latency of Off responses to principal whisker deflection. CTR did not change significantly following morphine exposure. Layer V neurons, on the other hand, did not show any significant changes in their spontaneous activity or their evoked responses following morphine exposure. Our results suggest that chronic morphine exposure has a subtle modulatory effect on response properties of neurons in barrel cortex.
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Hasegawa K, Ogawa H. Effects of acetylcholine on coding of taste information in the primary gustatory cortex in rats. Exp Brain Res 2006; 179:97-109. [PMID: 17109107 DOI: 10.1007/s00221-006-0772-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2006] [Accepted: 10/18/2006] [Indexed: 10/23/2022]
Abstract
Acetylcholine (ACh) receptors are widely distributed throughout the cerebral cortex in rats. Recently, cholinergic innervation of the gustatory cortex (GC) was reported to be involved in certain taste learning in rats. Here, the effects of iontophoretic application of ACh on the response properties of GC neurons were studied in urethane-anesthetized rats. ACh affected spontaneous discharges in a small fraction of taste neurons (11 of 86 neurons tested), but influenced taste responses in 27 of 43 neurons tested. No correlations with ACh susceptibility were noted for spontaneous discharges and taste responses. Among the 27 neurons, ACh facilitated taste responses in 13, inhibited taste responses in 13 and either facilitated or inhibited taste responses depending on the stimuli in 1. Furthermore, ACh affected the responses to best stimuli that produced the largest responses among four basic tastants (best responses) in 7 of 27 taste neurons, to non-best responses in 9, and to both best and non-best responses in 11. ACh mostly inhibited the best responses (13 of 18 neurons). Thus, ACh often decreased the response selectivity to the four basic tastants and changed the response profile. Atropine, a general antagonist of muscarinic receptors, antagonized ACh actions on taste responses or displayed the opposite effects on taste responses to ACh actions in two-thirds of the neurons tested. These findings indicate that ACh mostly modulates taste responses through muscarinic receptors, and suggest that ACh shifts the state of the neuron network in the GC, in terms of the response selectivities and response profiles.
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Affiliation(s)
- Kayoko Hasegawa
- Department of Sensory and Cognitive Physiology, Faculty of Medical and Pharmaceutical Sciences, Kumamoto University, Honjo 1-1-1, Kumamoto 860-8556, Japan.
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Liang K, Poytress BS, Chen Y, Leslie FM, Weinberger NM, Metherate R. Neonatal nicotine exposure impairs nicotinic enhancement of central auditory processing and auditory learning in adult rats. Eur J Neurosci 2006; 24:857-66. [PMID: 16848798 DOI: 10.1111/j.1460-9568.2006.04945.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Children of women who smoke cigarettes during pregnancy display cognitive deficits in the auditory-verbal domain. Clinical studies have implicated developmental exposure to nicotine, the main psychoactive ingredient of tobacco, as a probable cause of subsequent auditory deficits. To test for a causal link, we have developed an animal model to determine how neonatal nicotine exposure affects adult auditory function. In adult control rats, nicotine administered systemically (0.7 mg/kg, s.c.) enhanced the sensitivity to sound of neural responses recorded in primary auditory cortex. The effect was strongest in cortical layers 3 and 4, where there is a dense concentration of nicotinic acetylcholine receptors (nAChRs) that has been hypothesized to regulate thalamocortical inputs. In support of the hypothesis, microinjection into layer 4 of the nonspecific nAChR antagonist mecamylamine (10 microM) strongly reduced sound-evoked responses. In contrast to the effects of acute nicotine and mecamylamine in adult control animals, neither drug was as effective in adult animals that had been treated with 5 days of chronic nicotine exposure (CNE) shortly after birth. Neonatal CNE also impaired performance on an auditory-cued active avoidance task, while having little effect on basic auditory or motor functions. Thus, neonatal CNE impairs nicotinic regulation of cortical function, and auditory learning, in the adult. Our results provide evidence that developmental nicotine exposure is responsible for auditory-cognitive deficits in the offspring of women who smoke during pregnancy, and suggest a potential underlying mechanism, namely diminished function of cortical nAChRs.
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Affiliation(s)
- Kevin Liang
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA
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Marek GJ. A Novel Approach to the Identification of Psychiatric Drugs: Serotonin-Glutamate Interactions in the Prefrontal Cortex. CNS DRUG REVIEWS 2006. [DOI: 10.1111/j.1527-3458.2000.tb00148.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Metherate R, Kaur S, Kawai H, Lazar R, Liang K, Rose HJ. Spectral integration in auditory cortex: mechanisms and modulation. Hear Res 2005; 206:146-58. [PMID: 16081005 DOI: 10.1016/j.heares.2005.01.014] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2004] [Accepted: 01/06/2005] [Indexed: 11/19/2022]
Abstract
Auditory cortex contributes to the processing and perception of spectrotemporally complex stimuli. However, the mechanisms by which this is accomplished are not well understood. In this review, we examine evidence that single cortical neurons receive input covering much of the audible spectrum. We then propose an anatomical framework by which spectral information converges on single neurons in primary auditory cortex, via a combination of thalamocortical and intracortical "horizontal" pathways. By its nature, the framework confers sensitivity to specific, spectrotemporally complex stimuli. Finally, to address how spectral integration can be regulated, we show how one neuromodulator, acetylcholine, could act within the hypothesized framework to alter integration in single neurons. The results of these studies promote a cellular understanding of information processing in auditory cortex.
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Affiliation(s)
- Raju Metherate
- Department of Neurobiology and Behavior, University of California, Irvine, 2205 McGaugh Hall, Irvine, CA 92697-4550, United States.
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Pimlott SL, Piggott M, Ballard C, McKeith I, Perry R, Kometa S, Owens J, Wyper D, Perry E. Thalamic nicotinic receptors implicated in disturbed consciousness in dementia with Lewy bodies. Neurobiol Dis 2005; 21:50-6. [PMID: 16023355 DOI: 10.1016/j.nbd.2005.06.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Revised: 05/20/2005] [Accepted: 06/12/2005] [Indexed: 10/25/2022] Open
Abstract
Disturbances of consciousness (DOC) are common in dementia with Lewy bodies (DLB). Following previous findings of preserved temporal cortical high-affinity nicotinic binding relating to DOC, we investigated this receptor in thalamus, an area of high nicotinic receptor concentration, implicated in consciousness. 5-[125I]-A-85380 binding, primarily reflecting the alpha4beta2 subtype, was compared in 16 DLB patients with DOC and 6 without DOC, matched for duration and severity of dementia. Binding was higher in patients with DOC compared to patients without DOC in all thalamic nuclei examined, reaching significance in the reticular and ventral anterior thalamic nuclei. Comparing DLB patients with and without DOC to previously reported controls revealed similar binding levels in patients with DOC and lower binding in patients without DOC, reaching significance in the ventral anterior, indicating preserved nicotinic receptor density in DLB patients with DOC. These findings, together with previous neocortical data, implicate nicotinic modulation of thalamo-cortical circuitry as a key component in the control of conscious awareness in DLB.
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Affiliation(s)
- Sally L Pimlott
- West of Scotland Radionuclide Dispensary, Western Infirmary, Dumbarton Road, Glasgow G11 6NT, UK.
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17
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Rowe DL. A FRAMEWORK FOR INVESTIGATING THALAMOCORTICAL ACTIVITY IN MULTISTAGE INFORMATION PROCESSING. J Integr Neurosci 2005; 4:5-26. [PMID: 16035138 DOI: 10.1142/s0219635205000707] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2005] [Revised: 02/21/2005] [Indexed: 11/18/2022] Open
Abstract
A framework for investigating information processing in cortico-thalamocortical (cortico-TC) networks is presented, that in part can be used to model and interpret individual changes in electroencephalographic spectra and event-related potentials such as those from the Brain Resource International Database. Scientific work covering neurophysiology, TC firing modes, and TC models are explored in the framework to explain how the brain might process complex information in a multistage process. It is proposed that the thalamus and the cortico-TC system have unique ionic properties and transmission delays (in humans), which are suited to the function of taking "snapshots" or samples of complex environmental stimuli, rather than continuous data streams. This leads to careful and sequential coordination of stimulus and response processes, and increases the probability of information transfer and the resulting information complexity in higher cortical regions. Given the scope of this framework, the multidimensional and standardized Brain Resource International Database provides a pertinent set of measures for both testing hypotheses generated from the model, and for fitting the model to experimental data to investigate mechanisms underlying information processing.
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Affiliation(s)
- Donald L Rowe
- The Brain Dynamics Center, University of Sydney and Westmead Hospital, NSW 2145, Australia.
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18
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Castro-Alamancos MA. Dynamics of sensory thalamocortical synaptic networks during information processing states. Prog Neurobiol 2005; 74:213-47. [PMID: 15556288 DOI: 10.1016/j.pneurobio.2004.09.002] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2004] [Accepted: 09/08/2004] [Indexed: 10/26/2022]
Abstract
The thalamocortical network consists of the pathways that interconnect the thalamus and neocortex, including thalamic sensory afferents, corticothalamic and thalamocortical pathways. These pathways are essential to acquire, analyze, store and retrieve sensory information. However, sensory information processing mostly occurs during behavioral arousal, when activity in thalamus and neocortex consists of an electrographic sign of low amplitude fast activity, known as activation, which is caused by several neuromodulator systems that project to the thalamocortical network. Logically, in order to understand how the thalamocortical network processes sensory information it is essential to study its response properties during states of activation. This paper reviews the temporal and spatial response properties of synaptic pathways in the whisker thalamocortical network of rodents during activated states as compared to quiescent (non-activated) states. The evidence shows that these pathways are differentially regulated via the effects of neuromodulators as behavioral contingencies demand. Thus, during activated states, the temporal and spatial response properties of pathways in the thalamocortical network are transformed to allow the processing of sensory information.
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Affiliation(s)
- Manuel A Castro-Alamancos
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129, USA.
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19
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Roberts MJ, Zinke W, Guo K, Robertson R, McDonald JS, Thiele A. Acetylcholine dynamically controls spatial integration in marmoset primary visual cortex. J Neurophysiol 2004; 93:2062-72. [PMID: 15548624 PMCID: PMC1891447 DOI: 10.1152/jn.00911.2004] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent in vitro studies have shown that acetylcholine (ACh) selectively reduces the efficacy of lateral cortical connections via a muscarinic mechanism, while boosting the efficacy of thalamocortical/feed-forward connections via a nicotinic mechanism. This suggests that high levels of ACh should reduce center-surround interactions of neurons in primary visual cortex, making cells more reliant on feed-forward information. In line with this hypothesis, we show that local iontophoretic application of ACh in primate primary visual cortex reduced the extent of spatial integration, assessed by recording a neurons' length tuning. When ACh was externally applied, neurons' preferred length shifted toward shorter bars, showing reduced impact of the extra-classical receptive field. We fitted a difference and a ratio of Gaussian model to these data to determine the underlying mechanisms of this dynamic change of spatial integration. These models assume overlapping summation and suppression areas with different widths and gains to be responsible for spatial integration and size tuning. ACh significantly reduced the extent of the summation area, but had no significant effect on the extent of the suppression area. In line with previous studies, we also show that applying ACh enhanced the response in the majority of cells, especially in the later (sustained) part of the response. These findings are similar to effects of attention on neuronal activity. The natural release of ACh is strongly linked with states of arousal and attention. Our results may therefore be relevant to the neurobiological mechanism of attention.
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Affiliation(s)
- M J Roberts
- Psychology Brain and Behavior, University of Newcastle Upon Tyne, Newcastle Upon Tyne NE2 4HH, UK
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20
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Abstract
Acetylcholine release in sensory neocortex contributes to higher-order sensory function, in part by activating nicotinic acetylcholine receptors (nAChRs). Molecular studies have revealed a bewildering array of nAChR subtypes and cellular actions; however, there is some consensus emerging about the major nAChR subtypes and their functions in sensory cortex. This review first describes the systems-level effects of activating nAChRs in visual, somatosensory, and auditory cortex, and then describes, as far as possible, the underlying cellular and synaptic mechanisms. A related goal is to examine if sensory cortex can be considered a model system for cortex in general, because the use of sensory stimuli to activate neural circuits physiologically is helpful for understanding mechanisms of systems-level function and plasticity. A final goal is to highlight the emerging role of nAChRs in developing sensory cortex, and the adverse impact of early nicotine exposure on subsequent sensory-cognitive function.
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Affiliation(s)
- Raju Metherate
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, California 92697, USA.
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21
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Metherate R, Hsieh CY. Synaptic mechanisms and cholinergic regulation in auditory cortex. PROGRESS IN BRAIN RESEARCH 2004; 145:143-56. [PMID: 14650913 DOI: 10.1016/s0079-6123(03)45010-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Raju Metherate
- Department of Neurobiology and Behavior, University of California, 2205 McGaugh Hall, Irvine, CA 92697-4450, USA.
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22
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Clarke PB. Nicotinic modulation of thalamocortical neurotransmission. PROGRESS IN BRAIN RESEARCH 2003; 145:253-60. [PMID: 14650920 DOI: 10.1016/s0079-6123(03)45017-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Affiliation(s)
- Paul B Clarke
- Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir William Osler, Montreal, QC H3G 1Y6, Canada.
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23
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Metherate R, Hsieh CY. Regulation of glutamate synapses by nicotinic acetylcholine receptors in auditory cortex. Neurobiol Learn Mem 2003; 80:285-90. [PMID: 14521870 DOI: 10.1016/s1074-7427(03)00062-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Acetylcholine plays an important role in regulating the processing of sensory stimuli, and understanding its specific cellular actions is critical to understanding how sensory cortex develops and functions in different behavioral states. Here we review recent work on the cellular effects of nicotinic receptor activation in auditory cortex and describe how these actions could affect systems-level auditory function. In particular, we describe a novel function of nicotinic acetylcholine receptors to regulate glutamate synapses containing N-methyl-D-aspartate receptors during early postnatal development. The transient regulation of developing glutamate synapses also defines a window of vulnerability during which exposure to exogenous nicotine disrupts synapse development. Thus, it appears that nicotinic regulation of glutamate synapses is a critical feature of auditory cortex development.
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Affiliation(s)
- Raju Metherate
- Department of Neurobiology and Behavior, University of California, 2205 McGaugh Hall, Irvine 92697-4550, USA.
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24
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Oldford E, Castro-Alamancos MA. Input-specific effects of acetylcholine on sensory and intracortical evoked responses in the "barrel cortex" in vivo. Neuroscience 2003; 117:769-78. [PMID: 12617980 DOI: 10.1016/s0306-4522(02)00663-2] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The somatosensory neocortex processes extrinsic information from the thalamus and intrinsic information from local circuits. We compared the effects of acetylcholine (Ach) on neocortical field potential responses evoked by stimulation of the whiskers and by local electrical stimulation in the upper layers of the neocortex vibrissae representation ("barrel cortex") of adult rats anesthetized with urethane. In the barrel cortex, the cholinergic system was manipulated using microdialysis by exogenous application of Ach, by increasing the endogenous levels of Ach with physostigmine and by applying specific cholinergic agonists. The results revealed that Ach selectively enhances the sensory response relative to the intracortical response. Thus, pathways in the barrel cortex are differentially regulated by cholinergic inputs.
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Affiliation(s)
- E Oldford
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, 3801 University Street, Room WB210, Montreal, Quebec, Canada H3A 2B4
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25
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Lambe EK, Picciotto MR, Aghajanian GK. Nicotine induces glutamate release from thalamocortical terminals in prefrontal cortex. Neuropsychopharmacology 2003; 28:216-25. [PMID: 12589374 DOI: 10.1038/sj.npp.1300032] [Citation(s) in RCA: 206] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
It has been proposed that activation of nicotinic acetylcholine receptors (nAChRs) can activate the prefrontal cortex, enhancing attention and cognition. Nicotine can stimulate the release of several different neurotransmitters in many brain regions. In the present study, we found that stimulation of nAChRs by nicotine or the endogenous agonist, acetylcholine (ACh), induces a large spontaneous increase in glutamate release onto layer V pyramidal neurons of the prefrontal cortex. This release of glutamate, measured by spontaneous excitatory postsynaptic currents (sEPSCs) in the prefrontal cortical slice, depends on intact thalamocortical terminals. It can be suppressed by mu-opioids or eliminated by blocking action potentials. The increase in sEPSCs is sensitive to low concentrations of nicotine, suggesting the involvement of high-affinity (eg alpha(4)beta(2)) nAChRs. Recent work has shown alterations in prefrontal alpha(4)beta(2) nAChRs in autism and schizophrenia, two conditions that are distinguished by abnormal prefrontal cortical activation as well as difficulty in certain aspects of cognition and integrating social and emotional cues. We show that mice lacking the beta(2) nAChR subunit do not show increased sEPSCs with either nicotine or ACh, again implicating high-affinity nicotinic receptors. These findings give new insight into the mechanism by which nicotine affects excitatory neurotransmission to the output neurons of the cerebral cortex in a pathway that is critical for cognitive function and reward expectation.
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Affiliation(s)
- Evelyn K Lambe
- Departments of Psychiatry and Pharmacology, Yale School of Medicine, New Haven, CT, USA. evelyn.lambe@yaleedu
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26
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Graham A, Court JA, Martin-Ruiz CM, Jaros E, Perry R, Volsen SG, Bose S, Evans N, Ince P, Kuryatov A, Lindstrom J, Gotti C, Perry EK. Immunohistochemical localisation of nicotinic acetylcholine receptor subunits in human cerebellum. Neuroscience 2002; 113:493-507. [PMID: 12150770 DOI: 10.1016/s0306-4522(02)00223-3] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Neuronal nicotinic acetylcholine receptors are members of the ligand-gated ion channel superfamily composed of alpha and beta subunits with specific structural, functional and pharmacological properties. In this study we have used immunohistochemistry to investigate the presence of nicotinic acetylcholine receptor subunits in human cerebellum. Tissue was obtained at autopsy from eight adult individuals (aged 36-56 years). Histological sections were prepared from formalin-fixed paraffin-embedded material. alpha 3, alpha 4, alpha 6, alpha 7, beta 2, and beta 4 subunits were present in this brain area associated with both neuronal and non-neuronal cell types. Most Purkinje cells were immunoreactive for all the above subunits, but most strongly for alpha 4 and alpha 7. A proportion of granule cell somata were immunoreactive for all subunits except alpha 3. Punctate immunoreactivity in Purkinje cell and granule cell layers was evident with antibodies against alpha 3, alpha 4, alpha 6, and alpha 7 in parallel with synaptophysin immunoreactivity, suggesting the presence of these subunits on nerve terminals in the human cerebellum. All subunits were present in the dentate nucleus associated with neurones and cell processes. Strong immunoreactivity of neuropil in both the molecular and granule cell layers and within the dentate nucleus was noted with alpha 4, alpha 7 and beta 4 subunits. Astrocytes and astrocytic cell processes appeared to be immunoreactive for alpha 7 and cell processes observed in white matter, also possibly astrocytic, were immunoreactive for beta2. Immunoreactivity to all subunits was noted in association with blood vessels. We suggest that nicotinic acetylcholine receptor subunits may be involved in the modulation of cerebellar activity. Further investigations are warranted to evaluate the participation of nicotinic acetylcholine receptors in cerebellar pathology associated with both developmental and age-related disorders.
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Affiliation(s)
- A Graham
- Joint MRC-University of Newcastle upon Tyne, Centre Development in Clinical Brain Ageing, MRC Building, Newcastle General Hospital, Westgate Road, NE4 6BE, Newcastle upon Tyne, UK.
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27
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Pradhan AAA, Cumming P, Clarke PBS. [125I]Epibatidine-labelled nicotinic receptors in the extended striatum and cerebral cortex: lack of association with serotonergic afferents. Brain Res 2002; 954:227-36. [PMID: 12414106 DOI: 10.1016/s0006-8993(02)03340-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In rat extended striatum, most nicotinic cholinoceptors are likely to be presynaptic. A previous report suggested that DA and 5-HT afferents each account for at least 30% of nicotinic binding sites in the striatum. To explore this question further, rats received unilateral infusions of the neurotoxins 5,7-dihydroxytryptamine, 6-hydroxydopamine or vehicle into the medial forebrain bundle, and were sacrificed 3 weeks later. Denervation was quantified by [125I]RTI-55 autoradiography, using separate assay conditions that revealed DA and 5-HT transporters (i.e. DAT and SERT). Nicotinic cholinoceptors were quantified by [125I]epibatidine autoradiography. Infusion of 6-hydroxydopamine depleted DAT but not SERT labelling in all striatal areas (i.e. caudate-putamen, nucleus accumbens core and shell, olfactory tubercle). The serotonergic neurotoxin 5,7-dihydroxytryptamine depleted SERT and, to a lesser extent, DAT labelling. Both neurotoxins reduced [125I]epibatidine binding in striatal areas. Multiple linear regression analysis showed that these reductions in [125I]epibatidine binding were entirely associated with loss of DAT rather than SERT. The DAT-associated proportion of total [125I]epibatidine binding was 36+/-2% (caudate-putamen), 28+/-3% (accumbens core), 27+/-4% (accumbens shell) and 44+/-5% (olfactory tubercle). Cortical [125I]epibatidine binding was unaltered by 5,7-dihydroxytryptamine lesions that reduced SERT labelling by 46 to 73%. In all brain areas, even small (3.4 to 8.8%) SERT-associated reductions in [125I]epibatidine binding would have been detected as statistically significant. In conclusion, we report the failure to detect nAChRs on 5-HT terminals in extended striatum or cerebral cortex, using a sensitive [125I]epibatidine autoradiographic assay.
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Affiliation(s)
- Amynah A A Pradhan
- Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada H3G 1Y6
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28
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Ballard CG, Court JA, Piggott M, Johnson M, O'Brien J, McKeith I, Holmes C, Lantos P, Jaros E, Perry R, Perry E. Disturbances of consciousness in dementia with Lewy bodies associated with alteration in nicotinic receptor binding in the temporal cortex. Conscious Cogn 2002; 11:461-74. [PMID: 12435378 DOI: 10.1016/s1053-8100(02)00013-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Disturbances of consciousness, including fluctuations in attention and awareness, are a common and clinically important symptom in dementia with Lewy bodies (DLB). In the present study we investigate potential mechanisms of such disturbances of consciousness (DOC) in a clinicopathological study evaluating specific components of the cholinergic system. [3H]Epibatidine binding to the high-affinity nicotinic receptor in the temporal cortex (Brodmann's areas 20 and 36) differentiated DLB cases with and without DOC, being 62-66% higher in those with DOC (F=4.5,p=.025). The were no differences between DLB patients with or without DOC in 125I-labeled alpha-bungaratoxin binding to the low-affinity nicotinic receptor, [3H]pirenzepine binding to the muscarinic M1 receptor, or in choline acetyltransferase activity. These findings provide support for the hypothesis that cholinergic activity is an important neural correlate if consciousness and suggest a mechanism of DOC in DLB involving alterations in the nicotinic receptor, composed of predominantly alpha4 and beta2 subunits.
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Affiliation(s)
- Clive G Ballard
- Centre Development in Clinical Brain Aging, Newcastle General Hospital, Westgate Road, Newcastle upon Tyne NE4 6BE, London, UK
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29
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The role of Kv1.2-containing potassium channels in serotonin-induced glutamate release from thalamocortical terminals in rat frontal cortex. J Neurosci 2002. [PMID: 11739602 DOI: 10.1523/jneurosci.21-24-09955.2001] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Serotonin 5-HT(2A) receptors have been implicated in psychiatric illness and the psychotomimetic effects of hallucinogens. In brain slices, focal stimulation of 5-HT(2A) receptors in rat prefrontal cortex results in dramatically increased glutamate release onto layer V pyramidal neurons, as measured by an increase in "spontaneous" (nonelectrically evoked) EPSCs. This glutamate release is blocked by tetrodotoxin (TTX) and is thought to involve local spiking in thalamocortical axon terminals; however, the detailed mechanism has remained unclear. Here, we investigate parallels in EPSCs induced by either serotonin or the potassium channel blockers 4-aminopyridine (4-AP) or alpha-dendrotoxin (DTX). DTX, a selective blocker of Kv1.1-, Kv1.2-, and Kv1.6-containing potassium channels, has been shown to release glutamate in cortical synaptosomes, presumably by inhibiting a subthreshold-activated, slowly inactivating potassium conductance. By comparing DTX with other potassium channel blockers, we found that the ability to induce EPSCs in cortical pyramidal neurons depends on affinity for Kv1.2 subunits. DTX-induced EPSCs are similar to 5-HT-induced EPSCs in terms of sensitivity to TTX and omega-agatoxin-IVA (a blocker of P-type calcium channels) and laminar selectivity. The involvement of thalamocortical terminals in DTX-induced EPSCs was confirmed by suppression of these EPSCs by micro-opiates and thalamic lesions. More directly, DTX-induced EPSCs substantially occlude those induced by 5-HT, suggesting a common mechanism of action. No occlusion by DTX was seen when EPSCs were induced by a nicotinic mechanism. These results indicate that blockade of Kv1.2-containing potassium channels is part of the mechanism underlying 5-HT-induced glutamate release from thalamocortical terminals.
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30
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Marek GJ, Wright RA, Gewirtz JC, Schoepp DD. A major role for thalamocortical afferents in serotonergic hallucinogen receptor function in the rat neocortex. Neuroscience 2002; 105:379-92. [PMID: 11672605 DOI: 10.1016/s0306-4522(01)00199-3] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Activation of 5-hydroxytryptamine(2A) (5-HT(2A)) receptors by hallucinogenic drugs is thought to mediate many psychotomimetic effects including changes in affect, cognition and perception. Conversely, blockade of 5-HT(2A) receptors may mediate therapeutic effects of many atypical antidepressant and antipsychotic drugs. The purpose of the present study was to determine the source of subcortical glutamatergic afferents, which would project widely throughout the anterior-posterior axis of the rat brain to the apical dendrites of layer V pyramidal cells of the medial prefrontal cortex, from which serotonin induces transmitter release via activation of 5-HT(2A) receptors. Fiber-sparing chemical lesions of the medial thalamus selectively decreased the frequency of serotonin-induced excitatory postsynaptic currents recorded from layer V pyramidal cells in the prelimbic region of the medial prefrontal cortex by 60%. In contrast, large bilateral lesions of the amygdala did not alter the serotonin response. These thalamic lesions significantly decreased the amount of binding to either mu-opioid or metabotropic glutamate 2/3 receptors in the prelimbic region of the medial prefrontal cortex as expected from previous evidence that these agonists for these receptors suppress serotonin-induced excitatory postsynaptic currents by a presynaptic mechanism. Surprisingly, the amount of specific binding to cortical 5-HT(2A) receptors was significantly increased by the medial thalamic lesions. Thus, these experiments demonstrate that activation of cortical 5-HT(2A) receptors modulates transmitter release from thalamocortical terminals. Unexpectedly, lesioning the thalamocortical terminals also alters 5-HT(2A) receptor binding in the prefrontal cortex. These findings are of interest with respect to understanding therapeutic effects of antidepressant/antipsychotic drugs and the known behavioral effects of thalamic lesions in humans.
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MESH Headings
- Amygdala/cytology
- Amygdala/drug effects
- Amygdala/metabolism
- Animals
- Bridged Bicyclo Compounds/pharmacology
- Excitatory Amino Acid Agonists/pharmacology
- Excitatory Postsynaptic Potentials/drug effects
- Excitatory Postsynaptic Potentials/physiology
- Hallucinogens/pharmacology
- Male
- N-Methylaspartate/pharmacology
- Neural Pathways/cytology
- Neural Pathways/drug effects
- Neural Pathways/metabolism
- Prefrontal Cortex/cytology
- Prefrontal Cortex/drug effects
- Prefrontal Cortex/metabolism
- Pyramidal Cells/cytology
- Pyramidal Cells/drug effects
- Pyramidal Cells/metabolism
- Radioligand Assay
- Rats
- Rats, Sprague-Dawley
- Receptor, Serotonin, 5-HT2A
- Receptors, Metabotropic Glutamate/drug effects
- Receptors, Metabotropic Glutamate/metabolism
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- Receptors, Serotonin/drug effects
- Receptors, Serotonin/metabolism
- Serotonin/metabolism
- Serotonin/pharmacology
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
- Thalamus/cytology
- Thalamus/drug effects
- Thalamus/metabolism
- alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid/pharmacology
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Affiliation(s)
- G J Marek
- Department of Psychiatry, Yale University School of Medicine, New Haven CT 06508, USA.
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31
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Martin-Ruiz C, Court J, Lee M, Piggott M, Johnson M, Ballard C, Kalaria R, Perry R, Perry E. Nicotinic receptors in dementia of Alzheimer, Lewy body and vascular types. ACTA NEUROLOGICA SCANDINAVICA. SUPPLEMENTUM 2001; 176:34-41. [PMID: 11261803 DOI: 10.1034/j.1600-0404.2000.00305.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
OBJECTIVES Comparisons were made of nicotinic receptors in 3 major forms of dementia in old age. Although it is well established the involvement of nicotinic receptors in Alzheimer's disease (AD), their status in the other two main causes of dementia in old age-dementia with Lewy bodies (DLB) and vascular dementia (VaD) is not widely reported. METHODS Temporal cortex was examined for epibatidine and alpha-bungarotoxin binding, and immunoreactivity of alpha4 and alpha7 nAChR subunits. RESULTS There were selective abnormalities in nicotinic receptor subtypes in the disorders examined. In AD there is a loss of high affinity receptor binding, reflecting a selective loss of alpha4 subunit, but no change in alpha7 subunits. Similar abnormalities in ligand binding are also apparent in DLB. In the VaD series, there was no overall loss of epibatidine binding or immunoreactivity for alpha4 or alpha7 subunits. CONCLUSIONS Loss of cortical receptor alpha4 subunit appears to be a characteristic feature of neurodegenerative dementia but not dementia of vascular origin. Since nicotinic receptors control cerebral vasodilation, the relative integrity of the receptors in VaD may auger well for nicotinic therapy in this disorder in which there is a cholinergic abnormality, to judge by the loss of the presynaptic enzyme.
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Affiliation(s)
- C Martin-Ruiz
- Joint MRC-Newcastle University Development in Clinical Brain Aging, Newcastle General Hospital, Newcastle upon Tyne, UK
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32
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Court J, Martin-Ruiz C, Piggott M, Spurden D, Griffiths M, Perry E. Nicotinic receptor abnormalities in Alzheimer's disease. Biol Psychiatry 2001; 49:175-84. [PMID: 11230868 DOI: 10.1016/s0006-3223(00)01116-1] [Citation(s) in RCA: 176] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Loss of cortical nicotinic acetylcholine receptors with high affinity for agonists (20-50%) in patients with Alzheimer's disease is a common finding. Recent immunochemical analyses indicate that this deficit is predominantly associated with the loss of alpha4 subunits (30-50%), although modest reductions of alpha3 may occur in some individuals (25-29%). No reduction of beta2 subunit protein expression or levels of alpha3 and alpha4 messenger RNA has been reported. Decline in cortical [(125)I]alpha-bungarotoxin binding and alpha7 protein expression does not appear to be as extensive or widespread as the loss of alpha4 (0-40%), with no reduction in messenger RNA expression. In the thalamus, there was a trend for reduced [(3)H]nicotine binding in the majority of nuclei (0-20%) in Alzheimer's disease; however, there was a significant decline in [(125)I]alpha-bungarotoxin binding in the reticular nucleus. In the striatum [(3)H]nicotine binding was reduced in Alzheimer's disease, and although neuroleptic medication accentuated this change, it occurred in those free of neuroleptics. Changes in nicotinic acetylcholine receptors in Alzheimer's disease are distinct from those in normal aging and are likely to contribute to clinical features and possibly neuropathology.
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Affiliation(s)
- J Court
- Joint MRC Newcastle University Centre Development in Clinical Brain Aging, Institute for the Health of the Elderly, Newcastle General Hospital, Newcastle upon Tyne, United Kingdom
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Hsieh CY, Cruikshank SJ, Metherate R. Differential modulation of auditory thalamocortical and intracortical synaptic transmission by cholinergic agonist. Brain Res 2000; 880:51-64. [PMID: 11032989 DOI: 10.1016/s0006-8993(00)02766-9] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
To investigate synaptic mechanisms underlying information processing in auditory cortex, we examined cholinergic modulation of synaptic transmission in a novel slice preparation containing thalamocortical and intracortical inputs to mouse auditory cortex. Extracellular and intracellular recordings were made in cortical layer IV while alternately stimulating thalamocortical afferents (via medial geniculate or downstream subcortical stimulation) and intracortical afferents. Either subcortical or intracortical stimulation elicited a fast, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX)-sensitive, monosynaptic EPSP followed by long-duration, polysynaptic activity. The cholinergic agonist carbachol suppressed each of the synaptic potentials to different degrees. At low concentrations (5 microM) carbachol strongly reduced (>60%) the polysynaptic slow potentials for both pathways but did not affect the monosynaptic fast potentials. At higher doses (10-50 microM), carbachol also reduced the fast potentials, but reduced the intracortically-elicited fast potential significantly more than the thalamocortically-elicited fast potential, which at times was actually enhanced. Atropine (0.5 microM) blocked the effects of carbachol, indicating muscarinic receptor involvement. We conclude that muscarinic modulation can strongly suppress intracortical synaptic activity while exerting less suppression, or actually enhancing, thalamocortical inputs. Such differential actions imply that auditory information processing may favor sensory information relayed through the thalamus over ongoing cortical activity during periods of increased acetylcholine (ACh) release.
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Affiliation(s)
- C Y Hsieh
- Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA 92697-4550, USA
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34
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Kimura F. Cholinergic modulation of cortical function: a hypothetical role in shifting the dynamics in cortical network. Neurosci Res 2000; 38:19-26. [PMID: 10997574 DOI: 10.1016/s0168-0102(00)00151-6] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Wide innervation of cholinergic projections throughout the cortex implies that acetylcholine (ACh) plays an essential role in information processing, but how it works is still enigmatic. Experimental as well as theoretical work in the olfactory cortex and hippocampus suggests that ACh, via the muscarinic receptors, serves to shift the dynamics of the cortical networks into a state where afferent influence predominates over intracortical influence. Recent experiments in the visual and somatosensory cortex suggested that this hypothesis could be extended to neocortex. In addition, participation of the nicotinic receptors in regulating the synaptic response in the somatosensory cortex further substantiates this hypothesis. This hypothesis, derived mainly from in vitro work, also seemed to account for results from in vivo experiments without any obvious inconsistencies.
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Affiliation(s)
- F Kimura
- Department of Neuroscience, Biomedical Research Center, Osaka University Graduate School of Medicine, Suita, Japan
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Hellström-Lindahl E, Court JA. Nicotinic acetylcholine receptors during prenatal development and brain pathology in human aging. Behav Brain Res 2000; 113:159-68. [PMID: 10942042 DOI: 10.1016/s0166-4328(00)00210-2] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Nicotinic acetylcholine receptor (nAChRs) proteins and gene transcripts are already present in human prenatal brain and spinal cord at 4-6 weeks gestation, and a clear age-related increase in number of nAChRs was apparent during first trimester. In pons, there was also a parallel increase in the alpha7 mRNA level with age. The highest specific binding of [3H]epibatidine and [3H]cytisine was detected in spinal cord, pons and medulla oblongata, and binding of [125I]alpha-bungarotoxin was highest in spinal cord, medulla oblongata and mesencephalon. From the late fetal stage brain nAChRs have been shown to fall with increasing age. During aging (between 40 and 100 years) high affinity nicotine binding in the frontal cortex decreases in parallel with glutamate NMDA receptor binding ([3H]MK801). In the hippocampal formation and entorhinal cortex nicotine binding also declines with age, in common with [125I]alpha-bungarotoxin in the entorhinal cortex, but NMDA receptor binding remains unchanged. These reductions in nicotine binding with age may predispose the neo- and archicortex to the loss of nAChRs observed in age-associated neurodegenerative conditions. By contrast no loss in nAChR binding with aging is observed in the thalamus and only after the 70th decade in the striatum, although in Alzheimer's disease, Parkinson's disease and Lewy body dementia deficits in nAChRs are observed in these areas and may be associated with specific disease-related processes.
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Affiliation(s)
- E Hellström-Lindahl
- Department of Clinical Neuroscience, Occupational Therapy and Elderly Care Research, Karolinska Institutet, Huddinge University Hospital, Sweden.
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36
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Kimura F, Fukuda M, Tsumoto T. Acetylcholine suppresses the spread of excitation in the visual cortex revealed by optical recording: possible differential effect depending on the source of input. Eur J Neurosci 1999; 11:3597-609. [PMID: 10564367 DOI: 10.1046/j.1460-9568.1999.00779.x] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Optical recording with a voltage-sensitive dye was performed in visual cortical slices of the rat to determine the effect of acetylcholine (ACh) on the spread of excitation. In the presence of ACh, the spread of excitation initiated by stimulation at the white matter/layer VI (WM/VI) was greatly suppressed throughout the cortex, with less suppression in the middle layers. By comparing the effect of ACh with that of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), the fraction of the synaptic component that was sensitive to ACh was evaluated. ACh suppressed approximately 40-50% (maximum 55.8%, n = 11) of the initial synaptic component in the superficial and deep layers. In the middle, however, the effect was weakest and only approximately 20-30% (minimum 20.9%, n = 11) of the initial synaptic component was suppressed. On the basis of histological analysis, the region with the weakest ACh effect extended from upper V to lower II/III. To identify the site of ACh action in terms of pre- versus postsynaptic localization, exogenous glutamate was applied. Because ACh did not suppress the excitation induced by glutamate, the site of the ACh action was indicated to be presynaptic. When layer II/III was stimulated instead of WM/VI, the suppression was uniform throughout the cortex. A muscarinic receptor antagonist, atropine, blocked the suppression by ACh. In conclusion, our results indicate the following two points. First, ACh strongly suppresses intracortical connectivity through presynaptic muscarinic receptors. Secondly, in contrast to the intracortical connection, some group(s) of fibres, possibly thalamocortical afferents that arise from white matter and terminate in the middle cortical layers are suppressed much less by ACh. While ACh has been reported to have confusingly diverse effects, e.g. direct depolarization and hyperpolarization as well as synaptic facilitation and suppression, its effect on the propagation of excitation is very clear; suppression on intracortical connection, leaving thalamocortical inputs rather intact. We postulate that cholinergic innervation enables the afferent input to have a relatively dominant effect in the cortex.
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Affiliation(s)
- F Kimura
- Division of Neurophysiology, Department of Neurosciences, Biomedical Research Center, Osaka University Graduate School of Medicine, Suita, Japan.
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Gioanni Y, Rougeot C, Clarke PB, Lepousé C, Thierry AM, Vidal C. Nicotinic receptors in the rat prefrontal cortex: increase in glutamate release and facilitation of mediodorsal thalamo-cortical transmission. Eur J Neurosci 1999; 11:18-30. [PMID: 9987008 DOI: 10.1046/j.1460-9568.1999.00403.x] [Citation(s) in RCA: 160] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The modulatory influence of nicotinic acetylcholine receptor (nAChRs) on thalamocortical transmission was characterized in the prelimbic area (PrL) of the rat prefrontal cortex. In the first experiment, rats received a unilateral excitotoxic lesion centred on the mediodorsal thalamic nucleus (MD), and were sacrificed 1 week later. The lesion resulted in a 40% reduction of 3H-nicotine autoradiographic labelling in the ipsilateral prefrontal cortex, particularly in areas that are innervated by the MD. Electrophysiological experiments were subsequently performed in non-lesioned anaesthetized animals, in order to study modulation of short- and long-latency responses of PrL neurons evoked by electrical stimulation of the MD. The short-latency responses result from activation of the MD-PrL pathway and are mediated via AMPA-type glutamatergic receptors, whereas the long-latency responses reflect activation of the recurrent collaterals of cortical pyramidal neurons, Iontophoretic application of nicotinic agonists (nicotine, DMPP) facilitated both types of response. Local application of the nAChR antagonists dihydro-beta-erythroidine, mecamylamine and methyllycaconitine, prevented both kinds of facilitation. Finally, intracerebral microdialysis experiments were performed in order to test for nicotinic modulation of extracellular glutamate concentrations in the PrL. Direct application of nicotine via the dialysis probe increased glutamate levels in a dose-dependent manner. This effect was blocked by local perfusion of dihydro-beta-erythroidine. These findings therefore provide anatomical and functional evidence for nAChR-mediated modulation of thalamocortical input to the prefrontal cortex. Such a mechanism may be relevant to the cognitive effects of nicotine and nicotinic antagonists.
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Affiliation(s)
- Y Gioanni
- INSERM U114, Collège de France, Paris, France.
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38
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Marek GJ, Aghajanian GK. 5-Hydroxytryptamine-induced excitatory postsynaptic currents in neocortical layer V pyramidal cells: suppression by mu-opiate receptor activation. Neuroscience 1998; 86:485-97. [PMID: 9881863 DOI: 10.1016/s0306-4522(98)00043-8] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Activation of 5-hydroxytryptamine-2A receptors increases the frequency of excitatory postsynaptic currents through a focal action at apical, but not basilar, dendrites of neocortical layer V pyramidal cells. Since mu-, delta- and kappa-opiate receptors are known to inhibit depolarization-induced glutamate release in cerebrocortical slices, we examined the opiate receptor subtype(s) that suppress(es) 5-hydroxytryptamine-induced excitatory postsynaptic currents in the medial prefrontal cortex and whether this suppression was occurring through a presynaptic or a postsynaptic mechanism. Only opioid agonists that act upon mu-receptors (i.e. [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin, the endogenous mu-selective agonist endomorphin-1 and the non-selective opioid agonist [Met]enkephalin) suppressed 5-hydroxytryptamine-induced excitatory postsynaptic currents. The delta-agonist [D-phen(2,5)]enkephalin and the kappa-agonist U50,488 were ineffective. Only the selective mu-antagonist CTOP blocked the suppressant effect of enkephalin, while the selective delta-antagonist naltrindole and the selective kappa-antagonist norbinaltorphimine were ineffective. Since the 5-hydroxytryptamine-induced excitatory postsynaptic currents are mediated by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-type excitatory amino acid receptors, the failure of mu-agonists to either block postsynaptic AMPA responses or induce outward currents in layer V pyramidal cells suggest that mu-agonists are acting at a presynaptic site to block 5-hydroxytryptamine-induced excitatory postsynaptic currents. Strikingly, a regional selectivity in the suppressant effect of mu-receptor activation on 5-hydroxytryptamine-induced excitatory postsynaptic currents exists, as 300 nM [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin suppressed 5-hydroxytryptamine-induced excitatory postsynaptic currents in the medial prefrontal cortex by nearly 100%, while in the frontoparietal cortex 1 microM [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin suppressed 5-hydroxytryptamine-induced excitatory postsynaptic currents by only 58%. This is the first demonstration of a previously unsuspected physiological interaction between 5-hydroxytryptamine-2A and mu-opiate receptors and may be relevant to the relationship between these receptors and both mood and psychotic disorders.
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MESH Headings
- Animals
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
- Enkephalin, D-Penicillamine (2,5)-
- Enkephalin, Methionine/pharmacology
- Enkephalins/pharmacology
- Evoked Potentials/drug effects
- Evoked Potentials/physiology
- Excitatory Postsynaptic Potentials/drug effects
- Excitatory Postsynaptic Potentials/physiology
- In Vitro Techniques
- Male
- Models, Neurological
- Neocortex/physiology
- Pyramidal Cells/drug effects
- Pyramidal Cells/physiology
- Rats
- Rats, Sprague-Dawley
- Reaction Time
- Receptor, Serotonin, 5-HT2A
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/physiology
- Receptors, Serotonin/drug effects
- Receptors, Serotonin/physiology
- Serotonin/pharmacology
- Somatostatin/analogs & derivatives
- Somatostatin/pharmacology
- Synapses/drug effects
- Synapses/physiology
- alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid/pharmacology
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Affiliation(s)
- G J Marek
- Department of Psychiatry, Yale School of Medicine and the Connecticut Mental Health Center, New Haven 06508, USA
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39
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Abstract
Presynaptic nicotinic acetylcholine receptors (nAChRs) are present in many regions of the brain and potentially serve as targets for the pharmacological action of nicotine in vivo. To investigate their mechanism of action, we performed patch-clamp recordings in relay neurons from slices of thalamus sensory nuclei. In these nuclei, nAChR activation facilitated the release of the inhibitory neurotransmitter GABA. Micromolar concentrations of nicotinic agonists increased the frequency of miniature GABAergic synaptic currents and decreased the failure rate of evoked synaptic currents. These actions of nicotinic agonists were not observed in knock-out mice lacking the beta 2 nAChR subunit gene. Nicotinic effects were dependent on extracellular calcium ions, and they persisted when calcium was replaced by strontium or barium but not by magnesium. Furthermore, in high extracellular calcium concentrations, nicotinic agonists evoked an increase in spontaneous release lasting for minutes after removal of the agonist. This supports the view that presynaptic nAChRs facilitate the release of neurotransmitter by increasing the calcium concentrations in presynaptic nerve endings. With use of cadmium and nickel ions as selective blockers, it was found that in different sensory nuclei the presynaptic influx of calcium could result either from the activation of voltage-dependent calcium channels or from a direct influx through nAChR channels. Finally, we propose that the nicotinic facilitation of GABAergic transmission may contribute to the increase of signal-to-noise ratio observed in the thalamus in vivo during arousal.
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40
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Chessell IP, Pearson RC, Heath PR, Bown DM, Francis PT. Selective loss of cholinergic receptors following unilateral intracortical injection of volkensin. Exp Neurol 1997; 147:183-91. [PMID: 9294415 DOI: 10.1006/exnr.1997.6595] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Experimental lesions and quantitative autoradiography were used to investigate the cellular distribution of neurotransmitter receptors in rats. Lesions were produced by intracortical injections of either volkensin or ricin. However, only the former is retrogradely transported and volkensin treatment causes significant loss of contralateral cortical pyramidal neurones. Binding of [3H]pirenzepine (muscarinic M1 receptors) and [3H]nicotine was reduced in contralateral cortex in volkensin compared with ricin and/or control (uninjected) animals. However, binding of [3H]8-hydroxy-2-(n-dipropylamino)tetralin (5-HT1A receptors), [3H]ketanserin (5-HT2A receptors), and [3H]1,3-dipropylcyclopentylxanthine (adenosine A1 receptors) was unchanged. The most likely explanation for these results is that M1 and nicotinic receptors are present in large numbers on those pyramidal neurones that are lost. The results are discussed in terms of the biology of cortical pyramidal neurones, drugs for Alzheimer's disease, and novel ligands for improving human brain scanning techniques.
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Affiliation(s)
- I P Chessell
- Miriam Marks Department of Neurochemistry, Institute of Neurology, London, United Kingdom
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41
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Gil Z, Connors BW, Amitai Y. Differential regulation of neocortical synapses by neuromodulators and activity. Neuron 1997; 19:679-86. [PMID: 9331357 DOI: 10.1016/s0896-6273(00)80380-3] [Citation(s) in RCA: 428] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Synapses are continually regulated by chemical modulators and by their own activity. We tested the specificity of regulation in two excitatory pathways of the neocortex: thalamocortical (TC) synapses, which mediate specific inputs, and intracortical (IC) synapses, which mediate the recombination of cortical information. Frequency-sensitive depression was much stronger in TC synapses than in IC synapses. The two synapse types were differentially sensitive to presynaptic neuromodulators: only IC synapses were suppressed by activation of GABA(B) receptors, only TC synapses were enhanced by nicotinic acetylcholine receptors, and muscarinic acetylcholine receptors suppressed both synapse types. Modulators also differentially altered the frequency sensitivity of the synapses. Our results suggest a mechanism by which the relative strength and dynamics of input and associational pathways of neocortex are regulated during changes in behavioral state.
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Affiliation(s)
- Z Gil
- Department of Physiology, Zlotowski Center for Neuroscience, Ben-Gurion University, Beer-Sheva, Israel
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42
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Lavine N, Reuben M, Clarke PB. A population of nicotinic receptors is associated with thalamocortical afferents in the adult rat: laminal and areal analysis. J Comp Neurol 1997; 380:175-90. [PMID: 9100131 DOI: 10.1002/(sici)1096-9861(19970407)380:2<175::aid-cne3>3.0.co;2-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In the adult rat brain, a prominent population of nicotinic cholinoceptors binds 3H-nicotine with nanomolar affinity. These receptors are abundant in most thalamic nuclei and in neocortical layers 3/4, which receive a major thalamic input. To test whether cortical nicotinic receptors are associated with thalamocortical afferents, unilateral excitotoxic (N-methyl-D-aspartate) lesions were made in one of four thalamic nuclear groups (anterior, ventral, medial geniculate, or dorsal lateral geniculate) or in temporal cortex. After 1 or 4 weeks of survival, cortical 3H-nicotine binding was quantified via autoradiography. Thalamic lesions resulted in a partial loss of 3H-nicotine binding in ipsilateral cerebral cortex. In each thalamic lesion group, the greatest decrease (35-45%) occurred within the cortical layers and area (i.e., cingulate, parietal, temporal, or occipital cortex) receiving the densest thalamocortical innervation. Binding of 3H-nicotine was also reduced within the thalamus local to the lesion, particularly at the longer survival time. Saturation analysis, performed in frontoparietal cortical tissue homogenates following ventral thalamic lesions, revealed a significant (34%) reduction in receptor density but not affinity. Direct excitotoxic lesions of the neocortex (temporal cortex) tended to preserve 3H-nicotine binding in layers 3/4, despite local neuronal loss. These results, taken with other published findings, suggest that some nicotinic cholinoceptors in adult rat cerebral cortex are located on thalamocortical terminals. This organizing principle appears to apply not only to sensory and motor relay projections but also to association nuclei that project to allocortical areas. These receptors may provide a local mechanism for nicotinic cholinergic modulation of thalamocortical input.
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Affiliation(s)
- N Lavine
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada
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43
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Abstract
Thalamocortical synapses inform the cerebral neocortex about the external and internal worlds. The thalamus produces myriad thalamocortical pathways that vary in morphological, physiological, pharmacological and functional properties. All these features are of great importance for understanding how information is acquired, integrated, processed, stored and retrieved by the thalamocortical system. This paper reviews the properties of the afferents from thalamus to cortex, and identifies some of the gaps in our knowledge of thalamocortical pathways.
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44
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Vidal C. Nicotinic receptors in the brain. Molecular biology, function, and therapeutics. MOLECULAR AND CHEMICAL NEUROPATHOLOGY 1996; 28:3-11. [PMID: 8871936 DOI: 10.1007/bf02815199] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Although the psychological and physiological effects of nicotine have long suggested that nicotine exerts specific actions in the brain, the identification of neuronal nicotinic receptors (nAChRs) only began in the past few years with the development of molecular genetics. It is now clear that neuronal nAChRs form a family of highly heterogenous receptor subtypes, as evidenced by the number of genes encoding nAChR subunits, the diversity of immunopurified receptor proteins, and the multiple functional types of ligand-gated ion channels. Neuronal nAChRs have discrete localizations within the brain, and are involved in modulating neuronal firing and transmitter release. Cumulative evidence from animal and human studies indicates that nicotinic systems play a major role in higher cognitive functions and dysfunctions. In particular, the loss of cortical nAChRs is a neuro-chemical hallmark of Alzheimer (AD) and Parkinson (PD) diseases. In addition, nicotine improves memory and attention in Ad and PD. Our recent studies using electrophysiological biochemical and behavioral approaches suggest that the prefrontal cortex is a major target site for the cognitive actions of nicotine.
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Affiliation(s)
- C Vidal
- Institut Pasteur, Paris, France
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45
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Affiliation(s)
- M T Shipley
- Department of Anatomy, University of Maryland School of Medicine, Baltimore 21201, USA
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46
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Shipley MT, Zimmer LA, Ennis M, McLean JH. Chapter III The olfactory system. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s0924-8196(96)80005-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
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47
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Chessell IP, Humphrey PP. Nicotinic and muscarinic receptor-evoked depolarizations recorded from a novel cortical brain slice preparation. Neuropharmacology 1995; 34:1289-96. [PMID: 8570026 DOI: 10.1016/0028-3908(95)00096-o] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have developed a novel cortical brain slice preparation for extracellular field-potential recording using the grease-gap barrier technique. This preparation allows the study of cholinergic and glutamatergic depolarization responses of neocortical pyramidal neurones whose axons pass through the corpus callosum to contralateral cortical areas. Concentration-effect curves to carbachol, 1,1-dimethyl-4-phenyl piperazinium (DMPP) and muscarine yielded mean EC50 values of 29.5, 13.2 and 17.7 microM, respectively. Carbachol-induced responses were antagonized by both atropine and mecamylamine in a manner consistent with agonist effects of carbachol at both nicotinic and muscarinic sites, while concentration-effect curves to DMPP and muscarine were shifted rightward in a parallel manner by mecamylamine (10 microM) and atropine (5 nM), with antagonist pKB estimates of 6.4 and 9.0, respectively. Depolarization responses to glutamate were reversibly antagonized by D-2-amino-5-phosphonopentanoic acid and 6-cyano-7-nitroquinoxaline-2,3-dione; these antagonists had no effect on carbachol or DMPP-induced responses. This preparation allows reproducible quantification of depolarization responses of pyramidal neurones forming the corticocortical pathway, and indicates the presence of functional nicotinic and muscarinic receptors. We conclude that the preparation is a convenient model with which to test the efficacy of cholinomimetic agents in an intact neocortical system, and may be useful in the development of novel drugs for the treatment of the cognitive symptoms of Alzheimer's disease.
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Affiliation(s)
- I P Chessell
- Glaxo Institute of Applied Pharmacology, Department of Pharmacology, University of Cambridge, England
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48
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Summers KL, Giacobini E. Effects of local and repeated systemic administration of (-)nicotine on extracellular levels of acetylcholine, norepinephrine, dopamine, and serotonin in rat cortex. Neurochem Res 1995; 20:753-9. [PMID: 7566373 DOI: 10.1007/bf01705545] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Systemically administered (-)nicotine (0.2-1.2 mg/kg, s.c.) significantly increased the release of acetylcholine (ACh), norepinephrine (NE) and dopamine (DA) in rat cortex. The lowest dose of (-)nicotine examined (0.2 mg/kg, s.c.) also significantly elevated extracellular serotonin (5-HT) levels, and the maximal increases of extracellular ACh (122% at 90 min post injection) and DA levels (249% at 120 min post-injection) were observed following this dose. In contrast, the maximal increase of NE release (157% at 30 min post-injection) was observed following the highest dose of (-)nicotine injected (1.2 mg/kg, s.c.). This higher dose consistently produced generalized seizures. Repeating the (-)nicotine (0.58 mg/kg, s.c.) injection four hours after the first administration significantly elevated extracellular NE levels and also appeared to increase DA and ACh release. In addition, extracellular ACh and DA levels increased significantly in the dialysate after (-)nicotine was administered directly to the neocortex through the microdialysis probe membrane. Norepinephrine levels appeared to be elevated in the cortex following local administration as well.
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Affiliation(s)
- K L Summers
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield 62794-9230, USA
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49
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50
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Perry EK, Morris CM, Court JA, Cheng A, Fairbairn AF, McKeith IG, Irving D, Brown A, Perry RH. Alteration in nicotine binding sites in Parkinson's disease, Lewy body dementia and Alzheimer's disease: possible index of early neuropathology. Neuroscience 1995; 64:385-95. [PMID: 7700528 DOI: 10.1016/0306-4522(94)00410-7] [Citation(s) in RCA: 251] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
High-affinity nicotine binding, considered to primarily reflect the presence of CNS alpha 4 beta 2 nicotinic receptor subunits, was examined autoradiographically in brain regions most severely affected by Alzheimer and Parkinson types of pathology. In the midbrain, the high density of binding associated with the pars compacta of the substantia nigra was extensively reduced (65-75%, particularly in the lateral portion) in both Lewy body dementia and Parkinson's disease. Since loss of dopaminergic neurons in Lewy body dementia was only moderate (40%), loss or down-regulation of the nicotinic receptor may precede degeneration of dopaminergic neurons in this region. In the dorsolateral tegmentum, where diffuse cholinergic perikarya are located, nicotine binding was highly significantly decreased in both Lewy body dementia and Parkinson's disease with almost no overlap between the normal and disease groups, indicative of a major pathological involvement in or around the pedunculopontine cholinergic neurons. In the hippocampus, binding was decreased around the granular layer in Lewy body dementia and Alzheimer's disease, although unchanged in the stratum lacunosum moleculare, where binding was relatively higher. Dense bands of receptor binding in the presubiculum and parahippocampal gyrus--areas of highest binding in human cortex--were diminished in Alzheimer's disease but not Lewy body dementia. In temporal neocortex there were reductions in Alzheimer's disease throughout the cortical layers but in Lewy body dementia only in lower layers, in which Lewy bodies are concentrated. Abnormalities of the nicotinic receptor in the diseases examined appear to be closely associated with primary histopathological changes: dopaminergic cell loss in Parkinson's disease and Lewy body dementia, amyloid plaques and tangles in subicular and entorhinal areas in Alzheimer's disease. Loss or down-regulation of the receptor may precede neurodegeneration.
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Affiliation(s)
- E K Perry
- MRC Neurochemical Pathology Unit, Newcastle General Hospital, Newcastle upon Tyne, U.K
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