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Newman LA, Gold PE. Attenuation in rats of impairments of memory by scopolamine, a muscarinic receptor antagonist, by mecamylamine, a nicotinic receptor antagonist. Psychopharmacology (Berl) 2016; 233:925-32. [PMID: 26660295 PMCID: PMC4752895 DOI: 10.1007/s00213-015-4174-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 11/23/2015] [Indexed: 01/08/2023]
Abstract
RATIONALE Scopolamine, a muscarinic antagonist, impairs learning and memory for many tasks, supporting an important role for the cholinergic system in these cognitive functions. The findings are most often interpreted to indicate that a decrease in postsynaptic muscarinic receptor activation mediates the memory impairments. However, scopolamine also results in increased release of acetylcholine in the brain as a result of blocking presynaptic muscarinic receptors. OBJECTIVES The present experiments assess whether scopolamine-induced increases in acetylcholine release may impair memory by overstimulating postsynaptic cholinergic nicotinic receptors, i.e., by reaching the high end of a nicotinic receptor activation inverted-U dose-response function. RESULTS Rats tested in a spontaneous alternation task showed dose-dependent working memory deficits with systemic injections of mecamylamine and scopolamine. When an amnestic dose of scopolamine (0.15 mg/kg) was co-administered with a subamnestic dose of mecamylamine (0.25 mg/kg), this dose of mecamylamine significantly attenuated the scopolamine-induced memory impairments. We next assessed the levels of acetylcholine release in the hippocampus in the presence of scopolamine and mecamylamine. Mecamylamine injections resulted in decreased release of acetylcholine, while scopolamine administration caused a large increase in acetylcholine release. CONCLUSIONS These findings indicate that a nicotinic antagonist can attenuate impairments in memory produced by a muscarinic antagonist. The nicotinic antagonist may block excessive activation of nicotinic receptors postsynaptically or attenuate increases in acetylcholine release presynaptically. Either effect of a nicotinic antagonist-to decrease scopolamine-induced increases in acetylcholine output or to decrease postsynaptic acetylcholine receptor activation-may mediate the negative effects on memory of muscarinic antagonists.
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Affiliation(s)
- L A Newman
- Department of Biology, Syracuse University, 114 Life Sciences Complex, Syracuse, NY, 13244, USA
| | - P E Gold
- Department of Biology, Syracuse University, 114 Life Sciences Complex, Syracuse, NY, 13244, USA.
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Shin SS, Dixon CE. Alterations in Cholinergic Pathways and Therapeutic Strategies Targeting Cholinergic System after Traumatic Brain Injury. J Neurotrauma 2015; 32:1429-40. [PMID: 25646580 DOI: 10.1089/neu.2014.3445] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Traumatic brain injury (TBI) results in varying degrees of disability in a significant number of persons annually. The mechanisms of cognitive dysfunction after TBI have been explored in both animal models and human clinical studies for decades. Dopaminergic, serotonergic, and noradrenergic dysfunction has been described in many previous reports. In addition, cholinergic dysfunction has also been a familiar topic among TBI researchers for many years. Although pharmacological agents that modulate cholinergic neurotransmission have been used with varying degrees of success in previous studies, improving their function and maximizing cognitive recovery is an ongoing process. In this article, we review the previous findings on the biological mechanism of cholinergic dysfunction after TBI. In addition, we describe studies that use both older agents and newly developed agents as candidates for targeting cholinergic neurotransmission in future studies.
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Affiliation(s)
- Samuel S Shin
- 1 Brain Trauma Research Center, University of Pittsburgh , Pittsburgh, Pennsylvania.,2 Department of Neurological Surgery, University of Pittsburgh , Pittsburgh, Pennsylvania.,3 Safar Center for Resuscitation Research, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - C Edward Dixon
- 1 Brain Trauma Research Center, University of Pittsburgh , Pittsburgh, Pennsylvania.,2 Department of Neurological Surgery, University of Pittsburgh , Pittsburgh, Pennsylvania.,3 Safar Center for Resuscitation Research, University of Pittsburgh , Pittsburgh, Pennsylvania.,4 Veterans Affairs Pittsburgh Healthcare System , Pittsburgh, Pennsylvania
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Toscano-Márquez B, Dunn RJ, Krahe R. Distribution of muscarinic acetylcholine receptor mRNA in the brain of the weakly electric fishApteronotus leptorhynchus. J Comp Neurol 2013; 521:1054-72. [DOI: 10.1002/cne.23218] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 07/18/2012] [Accepted: 08/17/2012] [Indexed: 11/06/2022]
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Cholinergic modulation of cognition: insights from human pharmacological functional neuroimaging. Prog Neurobiol 2011; 94:360-88. [PMID: 21708219 PMCID: PMC3382716 DOI: 10.1016/j.pneurobio.2011.06.002] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Revised: 06/02/2011] [Accepted: 06/07/2011] [Indexed: 11/22/2022]
Abstract
Evidence from lesion and cortical-slice studies implicate the neocortical cholinergic system in the modulation of sensory, attentional and memory processing. In this review we consider findings from sixty-three healthy human cholinergic functional neuroimaging studies that probe interactions of cholinergic drugs with brain activation profiles, and relate these to contemporary neurobiological models. Consistent patterns that emerge are: (1) the direction of cholinergic modulation of sensory cortex activations depends upon top-down influences; (2) cholinergic hyperstimulation reduces top-down selective modulation of sensory cortices; (3) cholinergic hyperstimulation interacts with task-specific frontoparietal activations according to one of several patterns, including: suppression of parietal-mediated reorienting; decreasing ‘effort’-associated activations in prefrontal regions; and deactivation of a ‘resting-state network’ in medial cortex, with reciprocal recruitment of dorsolateral frontoparietal regions during performance-challenging conditions; (4) encoding-related activations in both neocortical and hippocampal regions are disrupted by cholinergic blockade, or enhanced with cholinergic stimulation, while the opposite profile is observed during retrieval; (5) many examples exist of an ‘inverted-U shaped’ pattern of cholinergic influences by which the direction of functional neural activation (and performance) depends upon both task (e.g. relative difficulty) and subject (e.g. age) factors. Overall, human cholinergic functional neuroimaging studies both corroborate and extend physiological accounts of cholinergic function arising from other experimental contexts, while providing mechanistic insights into cholinergic-acting drugs and their potential clinical applications.
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Blockade of 5-HT1B receptors facilitates contextual aversive learning in mice by disinhibition of cholinergic and glutamatergic neurotransmission. Neuropharmacology 2008; 54:1041-50. [DOI: 10.1016/j.neuropharm.2008.02.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Revised: 12/21/2007] [Accepted: 02/11/2008] [Indexed: 11/18/2022]
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Kokiko ON, Hamm RJ. A review of pharmacological treatments used in experimental models of traumatic brain injury. Brain Inj 2008; 21:259-74. [PMID: 17453754 DOI: 10.1080/02699050701209964] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PRIMARY OBJECTIVE We provide a review of recent chronic and delayed rehabilitative pharmacological treatments examined in experimental models of traumatic brain injury. There is a specific emphasis on studies aiming to enhance cognitive recovery. MAIN OUTCOMES AND RESULTS Decreased neuronal activity is believed to contribute to persistent cognitive disabilities. Neurotransmitter based rehabilitative treatments that increase neuronal activity may assist in the recovery of cognitive function. However, timing and dosage of drug treatment are influential in cognitive enhancement. Drug treatments that affect single and multiple neurotransmitter systems have the ability to significantly influence recovery of function following brain injury. CONCLUSIONS Understanding the relationship between neural disturbances and functional deficits following brain injury is challenging. Cognitive impairment may be the result of a single event or multiple events that occur after the initial insult. Increasing neuronal activity during the chronic phase of injury seems to be an effective treatment strategy for facilitating cognitive recovery. Pharmacological agents do not necessarily display the same effects in an injured brain as in a non-injured brain. Thus, further research is needed to establish the effectiveness of rehabilitative drug treatments.
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Affiliation(s)
- Olga N Kokiko
- Department of Psychology, Virginia Commonwealth University, Richmond, Virginia, USA
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Hayes J, Li S, Anwyl R, Rowan MJ. A role for protein kinase A and protein kinase M zeta in muscarinic acetylcholine receptor-initiated persistent synaptic enhancement in rat hippocampus in vivo. Neuroscience 2007; 151:604-12. [PMID: 18061357 DOI: 10.1016/j.neuroscience.2007.10.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2007] [Revised: 10/16/2007] [Accepted: 10/29/2007] [Indexed: 11/28/2022]
Abstract
Antagonists at presynaptic muscarinic autoreceptors increase endogenous acetylcholine (ACh) release and enhance cognition but little is known regarding their actions on plasticity at glutamatergic synapses. Here the mechanisms of the persistent enhancement of hippocampal excitatory transmission induced by the M2/M4 muscarinic ACh receptor antagonist methoctramine were investigated in vivo. The persistent facilitatory effect of i.c.v. methoctramine in the CA1 region of urethane-anesthetized rats was mimicked by gallamine, an M2 receptor antagonist, supporting a role for this receptor subtype. Neither the N-methyl-D-aspartate (NMDA) receptor antagonists D-(-)-2-amino phosphonopentanoic acid (d-AP5) and memantine, nor the metabotropic glutamate receptor subtype 1a antagonist (S)-(+)-alpha-amino-4-carboxy-2-methylbenzeneacetic acid (LY367385) significantly affected the methoctramine-induced persistent synaptic enhancement, indicating a lack of requirement for these glutamate receptors. The selective kinase inhibitors Rp-adenosine-3', 5'-cyclic monophosphorothioate (Rp-cAMPS) and the myrostylated pseudosubstrate peptide, Myr-Ser-Ile-Tyr-Arg-Arg-Gly-Ala-Arg-Arg-Trp-Arg-Lys-Leu-OH (ZIP), were used to investigate the roles of protein kinase A (PKA) and the atypical protein kinase C, protein kinase Mzeta (PKM zeta), respectively. Remarkably, pretreatment with either agent prevented the induction of the persistent synaptic enhancement by methoctramine and post-methoctramine treatment with Rp-cAMPS transiently reversed the enhancement. These findings are strong evidence that antagonism of M2 muscarinic ACh receptors in vivo induces an NMDA receptor-independent persistent synaptic enhancement that requires activation of both PKA and PKM zeta.
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Affiliation(s)
- J Hayes
- Department of Pharmacology and Therapeutics, Trinity College Institute of Neuroscience, Trinity College, Dublin 2, Ireland
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Sheardown MJ. Muscarinic M1receptor agonists and M2receptor antagonists as therapeutic targets in Alzheimer’s disease. Expert Opin Ther Pat 2005. [DOI: 10.1517/13543776.12.6.863] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Bennett HJ, White TD, Semba K. Activation of cholinergic and adrenergic receptors increases the concentration of extracellular adenosine in the cerebral cortex of unanesthetized rat. Neuroscience 2003; 117:119-27. [PMID: 12605898 DOI: 10.1016/s0306-4522(02)00826-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Adenosine is an inhibitory neuromodulator in the CNS. For extracellular adenosine to play a physiological role in the brain, it must be present at effective concentrations. Acetylcholine and noradrenaline are known to play an important role in modulating the activity of cortical neurons, and they might have a role also in the release of adenosine in the cerebral cortex in vivo. We examined whether activation of cholinergic and adrenergic receptors affects extracellular adenosine levels in the cerebral cortex of unanesthetized rats using in vivo microdialysis. All drugs were administered locally within the cortex by reverse dialysis. Both acetylcholine and the acetylcholinesterase inhibitor neostigmine increased extracellular adenosine levels, and the effect of neostigmine was blocked by the nicotinic receptor antagonist mecamylamine. Both nicotine and the nicotinic receptor agonist epibatidine increased the concentration of extracellular adenosine. Activation of muscarinic receptors using the nonselective agonist oxotremorine and a selective M1 receptor agonist also increased extracellular adenosine levels. Noradrenaline and the noradrenergic reuptake inhibitor desipramine increased extracellular adenosine levels. The alpha(1)-adrenergic receptor agonist phenylephrine and the beta-adrenergic agonist isoproterenol increased extracellular adenosine levels, whereas the alpha(2)-adrenergic receptor agonist clonidine did not have an effect. These findings indicate that activation of specific cholinergic and adrenergic receptors can increase extracellular levels of adenosine in the cortex, and suggest that cholinergic and adrenergic receptor-mediated regulation of adenosine levels may represent a mechanism for controlling the excitability of cortical neurons.
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Affiliation(s)
- H J Bennett
- Department of Anatomy and Neurobiology, Faculty of Medicine, Dalhousie University, Halifax, NS B3H 1X5, Canada
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Kozlowski JA, Zhou G, Tagat JR, Lin SI, McCombie SW, Ruperto VB, Duffy RA, McQuade RA, Crosby G, Taylor LA, Billard W, Binch H, Lachowicz JE. Substituted 2-(R)-methyl piperazines as muscarinic M(2) selective ligands. Bioorg Med Chem Lett 2002; 12:791-4. [PMID: 11859004 DOI: 10.1016/s0960-894x(02)00023-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A novel series of 2-(R)-methyl-substituted piperazines (e.g., 2) is described. They are potent M(2) selective ligands that have >100-fold selectivity versus the M(1) receptor. In the rat microdialysis assay, compound 14 showed significantly enchanced levels of acetylcholine after oral administration.
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11
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Alcantara AA, Mrzljak L, Jakab RL, Levey AI, Hersch SM, Goldman-Rakic PS. Muscarinic m1 and m2 receptor proteins in local circuit and projection neurons of the primate striatum: anatomical evidence for cholinergic modulation of glutamatergic prefronto-striatal pathways. J Comp Neurol 2001; 434:445-60. [PMID: 11343292 DOI: 10.1002/cne.1186] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The cellular and subcellular localization of muscarinic receptor proteins m1 and m2 was examined in the neostriatum of macaque monkeys by using light and electron microscopic immunocytochemical techniques. Double-labeling immunocytochemistry revealed m1 receptors in calbindin-D28k--positive medium spiny projection neurons. Muscarinic m1 labeling was dramatically more intense in the striatal matrix compartment in juvenile monkeys but more intense in striosomes in the adult caudate, suggesting that m1 expression undergoes a developmental age-dependent change. Ultrastructurally, m1 receptors were predominantly localized in asymmetric synapse-forming spines, indicating that these spines receive extrastriatal excitatory afferents. The association of m1-positive spines with lesion-induced degenerating prefronto-striatal axon terminals demonstrated that these afferents originate in part from the prefrontal cortex. The synaptic localization of m1 in these spines indicates a role of m1 in the modulation of excitatory neurotransmission. To a lesser extent, m1 was present in symmetric synapses, where it may also modulate inhibitory neurotransmission originating from local striatal neurons or the substantia nigra. Conversely, m2/choline acetyltransferase (ChAT) double labeling revealed that m2-positive neurons corresponded to large aspiny cholinergic interneurons and ultrastructurally, that the majority of m2 labeled axons formed symmetric synapses. The remarkable segregation of the m1 and m2 receptor proteins to projection and local circuit neurons suggests a functional segregation of m1 and m2 mediated cholinergic actions in the striatum: m1 receptors modulate extrinsic glutamatergic and monoaminergic afferents and intrinsic GABAergic afferents onto projection neurons, whereas m2 receptors regulate acetylcholine release from axons of cholinergic interneurons.
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Affiliation(s)
- A A Alcantara
- Section of Neurobiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
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12
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Kozlowski JA, Lowe DB, Guzik HS, Zhou G, Ruperto VB, Duffy RA, McQuade R, Crosby G, Taylor LA, Billard W, Binch H, Lachowicz JE. Diphenyl sulfoxides as selective antagonists of the muscarinic M2 receptor. Bioorg Med Chem Lett 2000; 10:2255-7. [PMID: 11055332 DOI: 10.1016/s0960-894x(00)00438-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Structure activity studies on [4-(phenylsulfonyl)phenyl]methylpiperazine led to the discovery of 4-cyclohexyl-alpha-[4-[[4-methoxyphenyl(S)-sufinyl]phenyl]-1-pi perazineacetonitrile, 1, an M2 selective muscarinic antagonist. Affinity at the cloned human M2 receptor was 2.7 nM; the M1/M2 selectivity is 40-fold.
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Affiliation(s)
- J A Kozlowski
- Schering-Plough Research Institute, Kenilworth, NJ 07033-0539, USA.
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Iannazzo L, Majewski H. M(2)/M(4)-muscarinic receptors mediate automodulation of acetylcholine outflow from mouse cortex. Neurosci Lett 2000; 287:129-32. [PMID: 10854729 DOI: 10.1016/s0304-3940(00)01163-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Acetylcholine outflow can be modulated through inhibitory presynaptic muscarinic autoreceptors. This study was to identify which subtype is involved in mouse cortex. Five muscarinic antagonists and their ability to elevate stimulation-induced (S-I) acetylcholine outflow were tested in the presence of neostigmine, which decreased S-I outflow. The potency of each antagonist was determined, expressed as a ratio of the potency of each other antagonist and compared with the potency ratios of the antagonists for each of the defined muscarinic receptors (M(1)-M(4)), as recorded in the literature. Linear regression analysis revealed that the data fitted the M(2) (r(2)>0.97) and M(4) (r(2)>0.85) subtypes best, with no correlation for the M(1) and M(3) subtypes.
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Affiliation(s)
- L Iannazzo
- Prince Henry's Institute of Medical Research, Clayton, Victoria, Australia.
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Gill TM, Gallagher M. Evaluation of muscarinic M2 receptor sites in basal forebrain and brainstem cholinergic systems of behaviorally characterized young and aged Long-Evans rats. Neurobiol Aging 1998; 19:217-25. [PMID: 9661996 DOI: 10.1016/s0197-4580(98)00048-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Aged (23-25-month-old) male Long-Evans rats were assessed for deficits in spatial cognition relative to young (4-6-month-old) rats. An in vitro autoradiography study was then conducted for muscarinic M2 sites using [3H]AF-DX 384 to assess binding in basal forebrain and brainstem areas where cholinergic neurons are localized. The analysis of basal forebrain included the medial septal/diagonal band region that provides cholinergic innervation of the hippocampus; the laterodorsal tegmental nucleus and pedunculopontine tegmental nucleus were analyzed in the brainstem. A significant age-related reduction in M2 binding was found in both the basal forebrain and brainstem. Only the reduction in the basal forebrain, however, was correlated with spatial learning impairment. Although the basal forebrain and brainstem cholinergic systems are each vulnerable in normal aging, contributions to the behavioral effects of aging may be distinctive for the two systems.
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Affiliation(s)
- T M Gill
- Department of Psychology, University of North Carolina, Chapel Hill 27599, USA
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Takahashi LK, Goh CS. Glucocorticoid facilitation of cholinergic development in the rat hippocampus. Neuroscience 1998; 83:1145-53. [PMID: 9502253 DOI: 10.1016/s0306-4522(97)00472-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The role of endogenous glucocorticoids in facilitating the postnatal innervation of septohippocampal cholinergic projections was examined. Septohippocampal cholinergic innervation was determined using two methods. One method involved measuring the optical density of acetylcholinesterase, a marker of cholinergic fibres in the hippocampus. In the other method, acetylcholinesterase-positive fibre counts were made in the hippocampus. Both methods revealed that 14-day-old rats adrenalectomized at 10 days of age have significantly lower densities of acetylcholinesterase in the hippocampal dentate gyrus molecular layer and in the regio inferior when compared to sham-operated control rats. This reduction in hippocampal acetylcholinesterase did not occur when 10-day-old adrenalectomized rats were either injected daily with exogenous corticosterone (0.3 mg/100 g body weight) or when adrenalectomy was conducted at later postnatal ages. In addition, unlike the developing hippocampus, the basolateral nucleus of the amygdala, which is also highly innervated by cholinergic fibres, showed no significant changes in acetylcholinesterase density after adrenalectomy. These observations suggest that glucocorticoids play an important role in supporting the development of cholinergic projections to the hippocampus. Cholinergic innervation of the hippocampus appears especially sensitive to the action of glucocorticoids occurring before the conclusion of the second postnatal week. Furthermore, this glucocorticoid influence is directed rather specifically to the hippocampus in comparison to the basolateral amygdala.
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Affiliation(s)
- L K Takahashi
- University of Wisconsin Medical School, Department of Psychiatry, Madison 53719-1179, USA
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Garrone B, Luparini MR, Tolu L, Magnani M, Landolfi C, Milanese C. Effect of the subchronic treatment with the acetylcholinesterase inhibitor heptastigmine on central cholinergic transmission and memory impairment in aged rats. Neurosci Lett 1998; 245:53-7. [PMID: 9596354 DOI: 10.1016/s0304-3940(98)00133-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The effect of subchronic administration of the acetylcholinesterase (AChE) inhibitor heptastigmine (HEP 0.6 mg/kg s.c. daily for 15 days) was investigated on cortical extracellular acetylcholine (ACh) levels and on memory function in aged male rats (26 months old at the beginning of the experiments) using microdialysis and behavioural techniques. Twenty-four hours after the last treatment, cortical ACh levels were significantly higher in rats subchronically treated with HEP than in rats treated with saline and AChE activity was still inhibited in cortex, hippocampus and striatum. The injection of a challenge dose of HEP (0.6 mg/kg s.c.) 24 h after the last treatment produced a faster and a more sustained increase of ACh in the cortex of subchronically treated rats compared to those repeatedly injected with saline. However, the maximum increase of ACh levels after injection of the challenge was comparable in both groups. In an object recognition test in which the pretest and test phase were spaced by 45 days, HEP prevented the deterioration of spatial memory occurring during this period, but had no effect on non-spatial memory. The present results suggest that moderate inhibition of brain AChE is able to maintain high levels of cortical extracellular ACh in aged rats and that this increase matches facilitatory effect of HEP on spatial memory.
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Affiliation(s)
- B Garrone
- Laboratory of Neuropharmacology, Angelini Research, Roma, Italy
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Khateb A, Fort P, Williams S, Serafin M, Jones BE, Mühlethaler M. Modulation of cholinergic nucleus basalis neurons by acetylcholine and N-methyl-D-aspartate. Neuroscience 1997; 81:47-55. [PMID: 9300400 DOI: 10.1016/s0306-4522(97)00167-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Known to exert an important modulatory influence on the cerebral cortex, the cholinergic neurons of the basal forebrain are modulated in turn by neurotransmitters which may include acetylcholine released from processes of brainstem or forebrain neurons. In the present study, we examined the effect of carbachol, a non-specific cholinergic agonist, either alone or in the presence of N-methyl-D-aspartate upon electrophysiologically identified cholinergic basalis neurons in guinea-pig basal forebrain slices. Carbachol produced a direct postsynaptic hyperpolarization, accompanied by a decrease in membrane resistance. Muscarine could mimic this hyperpolarizing effect, whereas nicotine produced a direct postsynaptic membrane depolarization. The interaction of carbachol with N-methyl-D-aspartate was subsequently tested since, in a prior study, N-methyl-D-aspartate was shown to induce rhythmic bursting in cholinergic cells when they were hyperpolarized by continuous injection of outward current. Applied simultaneously with N-methyl-D-aspartate in the absence of current injection, carbachol was also found to promote rhythmic bursting in half of the cells tested. Since the bursts under these conditions were markedly longer in duration than those observed in the presence of N-methyl-D-aspartate alone, it was hypothesized that carbachol might have another action, in addition to the membrane hyperpolarization. Using dissociated cells, it was found that brief applications of carbachol could indeed diminish the slow afterhyperpolarizations that follow single spikes, short bursts or long trains of action potentials in cholinergic basalis neurons. These results indicate that, through its dual ability to hyperpolarize cholinergic neurons and to reduce their afterhyperpolarizations, acetylcholine can promote the occurrence of rhythmic bursting in the presence of N-methyl-D-aspartate. Accordingly, whether derived from brainstem or local sources, acetylcholine may facilitate rhythmic discharge in cholinergic basalis neurons which could in turn impose a rhythmic modulation upon cortical activity during particular states across the sleep-waking cycle.
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Affiliation(s)
- A Khateb
- Département de Physiologie, CMU, Genève, Switzerland
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Messer WS, Abuh YF, Liu Y, Periyasamy S, Ngur DO, Edgar MA, El-Assadi AA, Sbeih S, Dunbar PG, Roknich S, Rho T, Fang Z, Ojo B, Zhang H, Huzl JJ, Nagy PI. Synthesis and biological characterization of 1,4,5,6-tetrahydropyrimidine and 2-amino-3,4,5,6-tetrahydropyridine derivatives as selective m1 agonists. J Med Chem 1997; 40:1230-46. [PMID: 9111297 DOI: 10.1021/jm960467d] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Previous studies identified several novel tetrahydropyrimidine derivatives exhibiting muscarinic agonist activity in rat brain. Such compounds might be useful in treating cognitive and memory deficits associated with low acetylcholine levels, as found in Alzheimer's disease. To determine the molecular features of ligands important for binding and activity at muscarinic receptor subtypes, the series of tetrahydropyrimidines was extended. Several active compounds were examined further for functional selectivity through biochemical studies of muscarinic receptor activity using receptor subtypes expressed in cell lines. Several amidine derivatives displayed high efficacy at m1 receptors and lower activity at m3 receptors coupled to phosphoinositide (PI) metabolism in A9 L cells. Four ligands, including 1b, 1f, 2b, and 7b, exhibited marked functional selectivity for m1 vs m3 receptors. Compound 1f also exhibited low activity at m2 receptors coupled to the inhibition of adenylyl cyclase in A9 L cells. Molecular modeling studies also were initiated to help understand the nature of the interaction of muscarinic agonists with the m1 receptor using a nine amino model of the m1 receptor. Several important interactions were identified, including interactions between the ester moiety and Thr192. Additional interactions were found for oxadiazoles and alkynyl derivatives with Asn382, suggesting that enhanced potency and selectivity may be achieved by maximizing interactions with Asp105, Thr192, and Asn382. Taken together, the data indicate that several amidine derivatives display functional selectivity for m1 muscarinic receptors, warranting further evaluation as therapeutic agents for the treatment of Alzheimer's disease. In addition, several amino acid residues were identified as potential binding sites for m1 agonists. These data may be useful in directing efforts to develop even more selective m1 agonists.
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Affiliation(s)
- W S Messer
- Department of Medicinal & Biological Chemistry, College of Pharmacy, The University of Toledo, Ohio 43606, USA
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Meier E, Frederiksen K, Nielsen M, Lemb�l HL, Pedersen H, Hyttel J. Pharmacological in vitro characterization of the arecoline bioisostere, Lu 25-109-T, a muscarinic compound with M1-agonistic and M2/M3-antagonistic properties. Drug Dev Res 1997. [DOI: 10.1002/(sici)1098-2299(199701)40:1<1::aid-ddr1>3.0.co;2-q] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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20
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Takahashi LK. Glucocorticoids and the hippocampus. Developmental interactions facilitating the expression of behavioral inhibition. Mol Neurobiol 1996; 13:213-26. [PMID: 8989771 DOI: 10.1007/bf02740624] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
When threatened, the rapid induction of fear and anxiety responses is adaptive. This article summarizes the current knowledge of the neurobiological development of behavioral inhibition, a prominent response occurring in fear and anxiety-provoking situations. In the rat, behavioral inhibition as exemplified by freezing first appears near the end of the second postnatal week. This emergence of freezing coincides with the developmental period marked by the rapid increase in plasma concentrations of glucocorticoids. Studies show that removal of glucocorticoids at this time severely impairs the age-dependent appearance of freezing. This behavioral impairment produced by adrenalectomy, however, is prevented by exogenous glucocorticoid administration. The effectiveness of glucocorticoids in facilitating the development of freezing appears to be caused by its actions in the hippocampus. In particular, glucocorticoids appear to play a vital role in the postnatal cellular development of the hippocampal dentate gyrus. Doses of glucocorticoids shown to reverse the behavioral inhibitory deficits occurring after adrenalectomy are ineffective when hippocampal dentate granule neurons are destroyed by neurotoxins. Notably, site-specific administration of glucocorticoids to the dorsal hippocampus is successful in promoting the occurrence of freezing in the adrenalectomized rat pup. It is hypothesized that glucocorticoids exert their behavioral inhibitory effects by influencing the development of the septohippocampal cholinergic system. Support for this hypothesis is derived from work demonstrating the importance of glucocorticoids on nerve growth factor systems that play a critical role in septohippocampal cholinergic survival.
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Affiliation(s)
- L K Takahashi
- Department of Psychiatry, University of Wisconsin Medical School, Madison 53719-1179, USA
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21
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Takahashi LK, Goh CS. Presynaptic muscarinic cholinergic receptors in the dorsal hippocampus regulate behavioral inhibition of preweanling rats. Brain Res 1996; 731:230-5. [PMID: 8883877 DOI: 10.1016/0006-8993(96)00684-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The aim of this research was to determine whether early maturation of the dorsal hippocampal cholinergic system mediates behavior exhibited by preweanling rats in the presence or absence of an unfamiliar adult male rat, a threatening stimulus. The behavioral responses that were examined included behavioral inhibition or freezing which emerges at 2 weeks of age and ultrasonic vocalizations. Prior to behavioral testing, oxotremorine, an M2 muscarinic receptor agonist that reduces cholinergic release from presynaptic terminals, was infused into the dorsal hippocampal dentate gyrus. Results demonstrated that 14-day-old rats with bilateral hippocampal infusions of a 1 microgram dose of oxotremorine exhibited significant deficits in freezing when exposed to the adult male rat. Importantly, oxotremorine had no significant effects on ultrasound emission and ambulatory activity when rat pups were tested in social isolation. Thus, effects of oxotremorine in the hippocampal dentate gyrus do not produce global changes in behavior. Results suggest that cholinergic release into the dorsal hippocampus facilitates the display of behavioral inhibition at the end of the second postnatal week. Behavioral deficits in freezing may reflect an oxotremorine-induced disruption of hippocampal cholinergic function underlying the processing of biologically relevant olfactory stimuli as well as mechanisms associated with attention.
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Affiliation(s)
- L K Takahashi
- Department of Psychiatry, University of Wisconsin Medical School, Madison 53719-1179, USA.
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22
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Bratt AM, Kelly ME, Domeney AM, Naylor RJ, Costall B. Acute and chronic arecoline: effects on a scopolamine-induced deficit in complex maze learning. Pharmacol Biochem Behav 1996; 53:713-21. [PMID: 8866976 DOI: 10.1016/0091-3057(95)02074-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
These studies tested the effect of arecoline, a nonselective muscarinic agonist, administered either acutely or by chronic peripheral infusion via osmotic minipumps, on a scopolamine-induced deficit in a Stone (14 unit) T-maze task in rats. Scopolamine alone (0.125-1.0 mg/kg, IP) dose-dependently impaired maze acquisition, increasing maze run-times and to a lesser extent, the number of errors committed. Neither acute administration of arecoline (5.0 and 10.0 mg/kg, IP), when tested against a deficit induced by scopolamine (0.25 mg/kg, IP), nor chronic arecoline administration (30 and 50 mg/kg per 24 h), when tested against a deficit induced by scopolamine (0.5 mg/kg), were able to ameliorate the decrements in maze performance. In fact, the higher dose of arecoline (50 mg/kg per 24 h) infused over 10 days potentiated the scopolamine-induced deficit, with respect to latency. These data indicate that dose selection is of great importance when employing arecoline in tests of learning and memory and that the influence of the method of administration of arecoline on the behavioural outcome warrants further study.
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Affiliation(s)
- A M Bratt
- School of Pharmacy, University of Bradford, West Yorkshire, UK. a.brattmail.psyc.memphis.edu
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23
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Mickala P, Boutin H, Bellanger C, Chevalier C, MacKenzie ET, Dauphin F. In vivo binding, pharmacokinetics and metabolism of the selective M2 muscarinic antagonists [3H]AF-DX 116 and [3H]AF-DX 384 in the anesthetized rat. Nucl Med Biol 1996; 23:173-9. [PMID: 8868291 DOI: 10.1016/0969-8051(95)02015-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The pharmacokinetics, in vivo binding and metabolism of two M2 muscarinic receptor antagonists, [3H]AF-DX 116 and [3H]AF-DX 384, were studied in anesthetized rats, which received either the tracer alone or following a saturating injection of atropine. Both radioligands were cleared from the circulation with distribution half-lives of 17 and 14 sec and elimination half-lives of 17 and 40 min for [3H]AF-DX 116 and [3H]AF-DX 384, respectively. A radioactive distribution, predominant in peripheral organs when compared to brain, was found at each time studied after tracer injection. Atropine-displaceable tracer uptake was evidenced at 20-40 min in brain (31%), submandibular glands (26%), spleen (37%) and notably heart (55%) for [3H]AF-DX 116 but only in heart (50%) for [3H]AF-DX 384 at 10-20 min. Regional brain sampling revealed a relatively uniform distribution of [3H]AF-DX 384 and a -45% atropine saturation effect (i.e., specific binding) in the thalamus 20 min after injection. Sequential thin-layer chromatographic studies performed on tissue extracts demonstrated the rapid appearance of labeled metabolites of both radiotracers in brain (but less so in liver) and especially in cardiac tissues, where almost 70% of total radioactivity still corresponded to authentic tracer 40 min after injection. Thus, based on their low blood-brain barrier permeability and the high presence of labeled metabolites in the central nervous system, AF-DX 116 and AF-DX 384 might be more helpful in the study of M2 muscarinic receptors present in heart rather than brain. Labeled with positron emittors, these M2 antagonists might be applicable to the pathophysiological study of disease states, such as cardiomyopathies.
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Affiliation(s)
- P Mickala
- Université de Caen, URA 1829 CNRS, Center Cyceron, France
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24
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Stillman MJ, Shukitt-Hale B, Galli RL, Levy A, Lieberman HR. Effects of M2 antagonists on in vivo hippocampal acetylcholine levels. Brain Res Bull 1996; 41:221-6. [PMID: 8924031 DOI: 10.1016/s0361-9230(96)00180-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
There is evidence that muscarinic receptors of the M2 subtype are presynaptic autoreceptors that modify the release of acetylcholine (ACh) through a negative feedback mechanism. Blocking these receptors by selective antagonists may therefore lead to increased ACh release. This in vivo microdialysis study examined the effects of three M2 antagonists, AF-DX 116, AF-DX 384, and AQ-RA 741, on hippocampal cholinergic neurotransmission. Drug (2, 4, 8, or 16 microM) or vehicle (Ringer's solution) was perfused via a microdialysis probe into the CA1 hippocampal region of conscious male Fischer 344 rats. Levels of ACh and choline were assessed by HPLC-EC. When the dose was expressed in K1 multiples, all drugs (except AQ-RA 741 at the two highest concentrations) were found to be on the same linear dose-response curve. Choline levels were not affected by drug administration. All three compounds elevated ACh levels in a similar K1-normalized dose-response fashion, strongly supporting the concept that the proposed presynaptic mechanism of action is indeed based on the same M2 receptor. Such elevations of ACh may not only improve performance on memory tasks, but may also have therapeutic advantages in conditions of cholinergic hypofunction, such as Alzheimer's disease.
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25
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Campbell V, Berrow N, Brickley K, Page K, Wade R, Dolphin AC. Voltage-dependent calcium channel beta-subunits in combination with alpha 1 subunits, have a GTPase activating effect to promote the hydrolysis of GTP by G alpha o in rat frontal cortex. FEBS Lett 1995; 370:135-40. [PMID: 7544301 DOI: 10.1016/0014-5793(95)00813-o] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The dihydropyridine-sensitive calcium channel agonist (-)-BayK 8644 was found to produce an enhancement of the intrinsic hydrolysis of GTP by Go in rat frontal cortex membranes. An anti-calcium channel beta-subunit antiserum abolished the (-)-BayK 8644-stimulated hydrolysis of GTP by Go and reduced the dihydropyridine binding capacity of the cortical membranes. A peptide which mimics the beta-subunit binding domain of the calcium channel complex, also attenuated (-)-BayK 8644 activation of GTPase. This study suggests that the calcium channel beta-subunit is the principal component of the channel complex involved in linking dihydropyridine agonist binding to enhanced hydrolysis of GTP by Go. This may be a mechanism by which calcium channels can normally act to limit the duration of a G-protein modulatory signal.
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Affiliation(s)
- V Campbell
- Department of Pharmacology, Royal Free Hospital School of Medicine, London, UK
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26
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Pike BR, Hamm RJ. Post-injury administration of BIBN 99, a selective muscarinic M2 receptor antagonist, improves cognitive performance following traumatic brain injury in rats. Brain Res 1995; 686:37-43. [PMID: 7583269 DOI: 10.1016/0006-8993(95)00448-y] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Mild to moderate traumatic brain injury (TBI) is associated with enduring impairments of cognitive function in both humans and animals. However, few experiments have investigated the role of post-injury pharmacologic strategies for attenuating the observed cognitive impairment after TBI. This investigation examined the effects of selective blockade of the presynaptic muscarinic M2 autoreceptor with BIBN 99 on cognitive recovery following rodent TBI. Experiment 1 investigated the effects of delayed post-injury administration of BIBN 99 on cognitive performance following moderate central fluid percussion TBI (2.1 +/- 0.05 atm). On days 11-15 after injury-cognitive performance was assessed with a Morris water maze (MWM) task. One hour before MWM testing injured rats were injected (s.c.) with either vehicle (n = 9), 0.5 (n = 8), or 1.0 (n = 8) mg/kg of BIBN 99. Results indicated that injured rats receiving the delayed post-injury treatment with BIBN 99 performed no better than injured-vehicle treated rats. In experiment 2, injured rats were injected (s.c.) once daily with either vehicle (n = 9), 0.5 (n = 9), or 1.0 (n = 9) mg/kg of BIBN 99 throughout the duration of the experiment beginning 24 h after TBI. Sham-injured animals injected (s.c.) with vehicle (n = 9) or 1.0 (n = 8) mg/kg of BIBN 99 were included for comparison. On days 11-15 after injury, cognitive performance was assessed with the MWM procedure. Results of the second experiment indicated that both doses of BIBN 99 were effective in attenuating cognitive deficits in the MWM as compared to the injured-vehicle treated animals (P < 0.05 for both comparisons).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- B R Pike
- Department of Psychology, Virginia Commonwealth University, Richmond 23284-842018, USA
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27
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Sirviö J, Riekkinen P, Jäkälä P, Riekkinen PJ. Experimental studies on the role of serotonin in cognition. Prog Neurobiol 1994; 43:363-79. [PMID: 7816931 DOI: 10.1016/0301-0082(94)90060-4] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- J Sirviö
- Department of Neurology, University of Kuopio, Finland
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28
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Quirion R, Richard J, Wilson A. Muscarinic and nicotinic modulation of cortical acetylcholine release monitored by in vivo microdialysis in freely moving adult rats. Synapse 1994; 17:92-100. [PMID: 8091306 DOI: 10.1002/syn.890170205] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The aim of the present study was to investigate, using in vivo dialysis, the existence of muscarinic and nicotinic receptors controlling acetylcholine release in the cortex of freely behaving rats. Various muscarinic receptor antagonists, including the nonselective blocker atropine, and a variety of M2 drugs (AF-DX116, AF-DX384, AQ-RA 741) potently stimulated, in a concentration-dependent manner, the in vivo release of acetylcholine in the rat cortex. The effects of all these antagonists were long lasting. The nature of these putative muscarinic autoreceptors is likely of the pharmacologically defined M2 subtype on the basis of the high potency of the antagonists of the AF-DX series and the variability and shorter duration of action of the effects of the prototypic M1 blocker, pirenzepine. 4-DAMP, a purported M3 blocker, also potently stimulated in vivo cortical acetylcholine release, but this likely relates to its now established, rather limited selectivity for any given muscarinic receptor subtypes. Peripheral and central injections of nicotine also induced the in vivo release of acetylcholine in the rat cortex, albeit with a lower potency and shorter duration of action than muscarinic antagonists. Interestingly, the combination of a muscarinic antagonist, such as atropine, AF-DX 116, or AF-DX384, in the presence of nicotine, induced tremendous releases of cortical acetylcholine up to 8- to 10-fold over basal values. This is clearly more than a simply additive effect, and it reveals the great capacity of cortical cholinergic nerve terminals to synthesize and release acetylcholine. Optimal pharmacological manipulations of these putative muscarinic and nicotinic autoreceptors could thus be useful in disorders in which the activity of cholinergic inputs is decreased, such as in Alzheimer's disease.
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Affiliation(s)
- R Quirion
- Neuroscience Division, Douglas Hospital Research Centre, Verdun, Québec, Canada
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29
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Milusheva E, Baranyi M, Zelles T, Mike A, Vizi ES. Release of acetylcholine and noradrenaline from the cholinergic and adrenergic afferents in rat hippocampal CA1, CA3 and dentate gyrus regions. Eur J Neurosci 1994; 6:187-92. [PMID: 7909482 DOI: 10.1111/j.1460-9568.1994.tb00260.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
An attempt was made to study the release of acetylcholine (ACh) and noradrenaline and their presynaptic modulation in isolated slice preparations dissected from different subfields of the hippocampus: CA1, CA3 and the dentate gyrus. The slices were perfused and loaded with [3H]choline or with [3H]noradrenaline. The release in response to field stimulation was determined radiochemically and the content of transmitters was assayed by a chemiluminescent method or by HPLC combined with electrochemical detection. After 30 min of loading with [3H]choline there were marked subregional differences in the specific activity of [3H]ACh content. The highest concentration was measured in the dentate gyrus and the lowest in CA3. Evidence was obtained that in all three subfields the cholinergic axon terminals are equipped with inhibitory muscarinic autoreceptors and the noradrenergic terminals with alpha 2-autoreceptors, as indicated by an increase in transmitter release when the tissue was exposed to selective muscarinic or alpha 2-adrenoceptor antagonists. In contrast, the cholinergic boutons are not equipped with alpha 2-adrenoceptors, and noradrenergic terminals do not possess inhibitory muscarinic receptors. It is therefore concluded that while the release of both ACh and noradrenaline is controlled by negative feedback modulation, there is no possibility of establishing a presynaptic inhibitory interaction between the two.
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Affiliation(s)
- E Milusheva
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest
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30
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Vilaró MT, Palacios JM, Mengod G. Multiplicity of muscarinic autoreceptor subtypes? Comparison of the distribution of cholinergic cells and cells containing mRNA for five subtypes of muscarinic receptors in the rat brain. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1994; 21:30-46. [PMID: 8164520 DOI: 10.1016/0169-328x(94)90375-1] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In situ hybridization was used to compare the microscopic distribution in the rat brain of cells containing mRNA for choline acetyltransferase (ChAT) (i.e. cholinergic cells) with that of cells containing mRNA for the five subtypes of muscarinic receptors, in an attempt to establish the potential role as autoreceptors (i.e. muscarinic cholinoceptors present in cholinergic cells) of the different muscarinic receptor subtypes. [32P]alpha-dATP-labelled synthetic oligonucleotides were used as hybridization probes in serial sections. Transcripts for all five subtypes of muscarinic receptors were detected in cells co-distributing with ChAT mRNA-containing cells in one or more regions of the brain. Cells containing m2, m3, m4 or m5 mRNAs were observed in the regions of the basal forebrain where cholinergic cells are located (medial septum/diagonal band nuclei, ventral pallidum, basal nucleus of Meynert). m2, m3 and m5 mRNAs were abundant in the parabigeminal nucleus. m2, m3 and m4 transcripts were detected in the pedunculopontine and laterodorsal tegmental nuclei. m1, m2 and m3 mRNAs were present in several cranial nerve nuclei. The present results suggest that muscarinic autoreceptors belonging to the five subtypes cloned to date may exist.
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31
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Doods H, Entzeroth M, Ziegler H, Schiavi G, Engel W, Mihm G, Rudolf K, Eberlein W. Characterization of BIBN 99: a lipophilic and selective muscarinic M2 receptor antagonist. Eur J Pharmacol 1993; 242:23-30. [PMID: 8223934 DOI: 10.1016/0014-2999(93)90005-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The present study was designed to characterize the receptor selectivity profile of the novel muscarinic M2 receptor antagonist BIBN 99 (5,11-dihydro-8-chloro-11-[[4-[3-[(2,2-dimethyl-1- oxopentyl)ethylamino]propyl]-1-piperidinyl]acetyl]-6H- pyrido[2,3-b][1,4]benzodiazepin-6-one). In radioligand binding studies BIBN 99 showed high affinity for m2/M2 sites (pKi = 7.52/7.57), intermediate affinity for m4 sites (pKi = 6.76) and low affinity for m1/M1 (pKi = 5.97/6.17), m3/M3 (pKi = 6.11/6.04) and m5 sites (pKi = 5.84). Functional studies in vitro showed BIBN 99 to be a competitive antagonist and to have an 11- to 25-fold higher affinity for M2 receptors than for putative M1 receptors in the rabbit vas deferens or M3 receptors in guinea-pig trachea. In vivo studies revealed that BIBN 99 is able to cross the blood-brain barrier, and although showing an approximately 3-fold higher affinity for M2 binding sites BIBN 99 appeared to be 7- to 18-fold less potent than AF-DX 116 in inhibiting muscarinic agonist or vagally induced bradycardia in rats and guinea-pigs. The results show that BIBN 99 is the first lipophilic muscarinic M2 receptor antagonist to have remarkable M2 versus M1 selectivity (30-fold). In addition, BIBN 99 possesses central nervous system activity and only minor peripheral cardiac effects.
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Affiliation(s)
- H Doods
- Department of Pharma Research, Dr. Karl Thomae GmbH, Biberach, Germany
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32
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Flynn DD, Mash DC. Distinct kinetic binding properties of N-[3H]-methylscopolamine afford differential labeling and localization of M1, M2, and M3 muscarinic receptor subtypes in primate brain. Synapse 1993; 14:283-96. [PMID: 8248852 DOI: 10.1002/syn.890140406] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Three classes of muscarinic receptors in mammalian brain have been postulated on the basis of equilibrium and kinetic binding data. However, equilibrium binding assays alone have not permitted a clear demonstration of the localization of putative M1, M2, and M3 receptor subtypes in the brain because of the overlapping affinities of virtually all muscarinic antagonists. In the present study, the conditions for selective occupancy of the M1, M2, and M3 receptor subtypes in the brain of the rhesus monkey were based on the distinct kinetic and equilibrium binding properties of N-[3H]-methylscopolamine (NMS) at cloned m1-m4 muscarinic receptor subtypes expressed in A9L transfected cells. Quantitative autoradiography of the M1, M2, and M3 muscarinic receptor subtypes in the primate brain was performed according to the following strategy. The M1 (m1) receptor subtype was labeled directly with a non-saturating concentration of [3H]-pirenzepine. The M2 (m2) subtype was labeled by incubations consisting of short, two minute pulses of [3H]-NMS after a preincubation with 0.3 microM pirenzepine to occlude m1, m3, and m4 sites. Selective occupancy of the M3 (m3) receptor (subtype) was achieved by pre-incubation with 0.5 nM unlabeled NMS to partially occlude the m1, m2, and m4 sites, equilibrium with 0.5 nM [3H]-NMS, followed by a 60 minute tracer dissociation in the presence of 1 microM atropine. In vitro autoradiography demonstrated that the M1 receptor subtype was confined to forebrain structures. M1 receptors were prevalent throughout the cerebral cortical mantle, amygdala, hippocampus, and the striatum. Low to background levels of the M1 receptor subtype were measured over the thalamus, hypothalamus, and brainstem. The M2 subtype was widely distributed with elevated densities of binding sites seen over all primary sensory cortical areas, and within discrete thalamic, hypothalamic, and brainstem nuclei. The distribution of the M3 receptor subtype was largely coincident with the pattern of the M1 sites labeled by non-saturating concentrations of [3H]-pirenzepine with some notable exceptions. Within the cerebral cortical mantle, the M3 receptor exhibited an elevated gradient over the orbitofrontal gyrus and the temporal lobe. Within the striatum, the M3 subtype was elevated over the anterior and dorsal part of the caudate nucleus, while the M1 receptors were most prevalent over the ventromedial sector. Selective labeling of M3 receptors was seen over the medial division of the globus pallidus and within the substantia nigra pars reticulata. In contrast to the pattern of the M1 receptor subtype, M3 receptors were prevalent also over midline nuclei of the hypothalamus.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- D D Flynn
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Florida 33101
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33
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Price DL, Koliatsos VE, Clatterbuck RC. Cholinergic systems: human diseases, animal models, and prospects for therapy. PROGRESS IN BRAIN RESEARCH 1993; 98:51-60. [PMID: 8248537 DOI: 10.1016/s0079-6123(08)62380-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- D L Price
- Department of Pathology and Neurology, Johns Hopkins University School of Medicine, Baltimore, MD
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34
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Doods HN, Quirion R, Mihm G, Engel W, Rudolf K, Entzeroth M, Schiavi GB, Ladinsky H, Bechtel WD, Ensinger HA. Therapeutic potential of CNS-active M2 antagonists: novel structures and pharmacology. Life Sci 1993; 52:497-503. [PMID: 8441330 DOI: 10.1016/0024-3205(93)90307-o] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Clinical trials with muscarinic agonists or acetylcholine esterase inhibitors for the treatment of Alzheimer's dementia have shown disappointing or equivocal results. An alternative treatment of this disease is the development of drugs which enhance the release of acetylcholine. It is believed, that of the five muscarinic receptor subtypes so far identified in the brain, M2 receptors are located presynaptically in the cortex and hippocampus and upon stimulation inhibit the release of acetylcholine. Based on this hypothesis, we initiated a drug discovery program with the aim of identifying selective and centrally active M2 antagonists which are capable of enhancing cholinergic transmission. These efforts resulted in the successful design and synthesis of novel muscarinic antagonists able to cross the blood brain barrier. Moreover, these compounds show few peripheral effects and possess a superior M2 versus M1 selectivity. The prototype of this novel class of M2 selective compounds, BIBN 99, could be a valuable tool to test the hypothesis that lipophilic M2 antagonists show beneficial effects in the treatment of cognitive disorders.
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Affiliation(s)
- H N Doods
- Dr Karl Thomae GmbH, Biberach/Riss, Germany
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35
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Chapter 7 Muscarinic acetylcholine receptors. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/s0167-7306(08)60360-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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36
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Riekkinen M, Riekkinen P, Sirviö J, Riekkinen P. Effects of combined methysergide and mecamylamine/scopolamine treatment on spatial navigation. Brain Res 1992; 585:322-6. [PMID: 1511316 DOI: 10.1016/0006-8993(92)91229-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In the present study, we investigated the effects of a 5-HT2 receptor antagonist, methysergide (2.5, 7.5 and 20 mg/kg), on spatial learning in saline, mecamylamine (10 mg/kg) and scopolamine (0.8 mg/kg) treated rats. Methysergide had no effect on water-maze (WM) spatial learning in rats subjected to saline or mecamylamine pretreatments. However, scopolamine-induced WM learning deficit was augmented by methysergide at doses of 7.5 and 20 mg/kg. These results further suggest (A) that cholinergic and serotonergic systems may interact in the regulation of spatial learning, and (B) that the cholinergic component of this interaction with serotonin2 receptors is mediated by muscarinic receptors, but not by nicotinic receptors.
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Affiliation(s)
- M Riekkinen
- University of Kuopio, Department of Neurology, Finland
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37
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Baux G, Fossier P. [Release of acetylcholine and its regulation]. ARCHIVES INTERNATIONALES DE PHYSIOLOGIE, DE BIOCHIMIE ET DE BIOPHYSIQUE 1992; 100:A3-15. [PMID: 1382687 DOI: 10.3109/13813459209000708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The mechanism of acetylcholine (ACh) release and its regulation is a widely studied subject still underdebated. Although the vesicular hypothesis for ACh release is at present largely accepted, alternative theories have been proposed. ACh release is triggered by calcium influx through specific presynaptic Ca2+ channels. The modulation of this calcium influx appears as the main mechanism through which ACh release is regulated. This can be achieved by direct modification of the presynaptic Ca2+ channel opening or indirectly by a change in the polarization level of the presynaptic membrane due to the opening or closing of other presynaptic channels (usually K+ channels). The increase in the intracellular Ca2+ concentration that triggers ACh release is also under the control of Ca2+ membrane exchanges and intracellular Ca2+ buffers. ACh synthesis that takes place in the cytoplasm of the terminal, can itself be modulated leading to changes in the quantity of ACh available for release. All these regulatory mechanisms can be initiated by the activation of presynaptic receptors to either ACh itself (autoreceptors) or to other transmitters (heteroreceptors). Most often, these presynaptic receptors seem to require the transducing role of G proteins and the involvement of various second messengers. Some illnesses concerning the cholinergic system can be related to a disfunction of one of these presynaptic regulatory mechanisms.
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Affiliation(s)
- G Baux
- Laboratoire de Neurobiologie cellulaire et moléculaire, C.N.R.S., Gif sur Yvette, France
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Lallement G, Denoyer M, Collet A, Pernot-Marino I, Baubichon D, Monmaur P, Blanchet G. Changes in hippocampal acetylcholine and glutamate extracellular levels during soman-induced seizures: Influence of septal cholinoceptive cells. Neurosci Lett 1992; 139:104-7. [PMID: 1357600 DOI: 10.1016/0304-3940(92)90868-8] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The changes in extracellular acetylcholine and glutamate levels were determined, during the course of seizures induced by soman, an irreversible inhibitor of acetylcholinesterase, in the CA1 hippocampal area of rats previously injected with atropine or normal saline into septum. The marked increases observed in soman-treated animals were abolished in rats receiving atropine. These data strongly suggest that, during soman intoxication, septal cholinoceptive cells play a key role in controlling the release of acetylcholine and glutamate in hippocampus. The mechanisms underlying this phenomenon are discussed.
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Affiliation(s)
- G Lallement
- Centre de Recherches du Service de Santé des Armées, Unité de Neurotoxicologie, La Tronche, France
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Gibbs RB, Pfaff DW. Effects of estrogen and fimbria/fornix transection on p75NGFR and ChAT expression in the medial septum and diagonal band of Broca. Exp Neurol 1992; 116:23-39. [PMID: 1313767 DOI: 10.1016/0014-4886(92)90173-n] [Citation(s) in RCA: 124] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
NGF receptor-expressing cells located in the basal forebrain have recently been shown to contain estrogen (E) receptors (Toran-Allerand and MacLusky. 1989. Soc. Neurosci. Abstr. 15: 954). In the present study, we have examined the effects of E-treatment on p75NGFR and choline acetyltransferase (ChAT) expression by neurons in the medial septum (MS) and the vertical (VDB) and horizontal (HDB) limbs of the diagonal band of Broca using immunocytochemical and in situ hybridization techniques. First, since E-treatment has been shown to affect neuronal survival and to stimulate synaptic reorganization and growth within various regions of the brain, we hypothesized that E-treatment might attenuate the loss of p75NGFR immunoreactivity (IR) which occurs in the MS and VDB following transection of the fimbria/fornix. Contrary to our hypothesis, E-treatment did not attenuate the effects of fimbria/fornix transection. In fact, E-treatment alone produced a significant decrease in the number of p75NGFR-IR cells detected in the MS. Subsequent experiments confirmed that chronic E-treatment produces a down-regulation of both p75NGFR-IR and p75NGFR mRNA in the MS and VDB. In the MS, estrogen appeared to affect a subpopulation of p75NGFR-expressing neurons which were also affected by fimbria/fornix transection since the effects of these two treatments were not additive. In addition, effects of E-treatment on p75NGFR-IR were sex-specific (observed in females but not in males) and were reversible in the MS after 2 weeks, but not after 4 weeks (allowing 2 weeks recovery), of E-treatment. A time-course analysis revealed that effects of E-treatment on p75NGFR-IR were not observed until after 16 days (MS) or 30 days (VDB) of E-treatment and were preceded by a significant and transient increase in ChAT expression in both the MS and VDB. The data are consistent with the possibility that continuous, long-term exposure to gonadal steroids may contribute to a loss of p75NGFR-expressing neurons with age. In addition, the data suggest that p75NGFR expression may play a role in regulating the functioning of specific basal forebrain cholinergic neurons. Different mechanisms by which E-treatment might influence ChAT and p75NGFR expression in brain are discussed.
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Affiliation(s)
- R B Gibbs
- Laboratory of Neurobiology and Behavior, The Rockefeller University, 1230 York Avenue, New York, New York 10021
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Vilaró MT, Wiederhold KH, Palacios JM, Mengod G. Muscarinic M2 receptor mRNA expression and receptor binding in cholinergic and non-cholinergic cells in the rat brain: a correlative study using in situ hybridization histochemistry and receptor autoradiography. Neuroscience 1992; 47:367-93. [PMID: 1641129 DOI: 10.1016/0306-4522(92)90253-x] [Citation(s) in RCA: 175] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The goal of the present study was to identify the cells containing mRNA coding for the m2 subtype of muscarinic cholinergic receptors in the rat brain. In situ hybridization histochemistry was used, with oligonucleotides as hybridization probes. The distribution of cholinergic cells was examined in consecutive sections with probes complementary to choline acetyltransferase mRNA. Furthermore, the microscopic distribution of muscarinic cholinergic binding sites was examined with a non-selective ligand ([3H]N-methylscopolamine) and with ligands proposed to be M1-selective ([3H]pirenzepine) or M2-selective ([3H]oxotremorine-M). The majority of choline acetyltransferase mRNA-rich (i.e. cholinergic) cell groups (medial septum-diagonal band complex, nucleus basalis, pedunculopontine and laterodorsal tegmental nuclei, nucleus parabigeminalis, several motor nuclei of the brainstem, motoneurons of the spinal cord), also contained m2 mRNA, strongly suggesting that at least a fraction of these receptors may be presynaptic autoreceptors. A few groups of cholinergic cells were an exception to this fact: the medial habenula and some cranial nerve nuclei (principal oculomotor, trochlear, abducens, dorsal motor nucleus of the vagus). Furthermore, m2 mRNA was not restricted to cholinergic cells but was also present in many other cells throughout the rat brain. The distribution of m2 mRNA was in good, although not complete, agreement with that of binding sites for the M2 preferential agonist [3H]oxotremorine-M, but not with [3H]pirenzepine binding sites. Regions where the presence of [3H]oxotremorine-M binding sites was not correlated with that of m2 mRNA are the caudate-putamen, nucleus accumbens, olfactory tubercle and islands of Calleja. The present results strongly suggest that the M2 receptor is expressed by a majority of cholinergic cells, where it probably plays a role as autoreceptor. However, many non-cholinergic neurons also express this receptor, which would be, presumably, postsynaptically located. Finally, comparison between the distribution of m2 mRNA and that of the proposed M2-selective ligand [3H]oxotremorine-M indicates that this ligand, in addition to M2 receptors, may also recognize in certain brain areas other muscarinic receptor populations, particularly M4.
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Affiliation(s)
- M T Vilaró
- Preclinical Research, Sandoz Pharma Ltd., Basel, Switzerland
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Messer WS, Bohnett M, Stibbe J. Evidence for a preferential involvement of M1 muscarinic receptors in representational memory. Neurosci Lett 1990; 116:184-9. [PMID: 2259447 DOI: 10.1016/0304-3940(90)90407-z] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The effects of intrahippocampal injections to the M1-selective antagonist pirenzepine and the M2-selective antagonist AF-DX 116 were examined on performance of a representational memory task in rats. Although both antagonists impaired performance, pirenzepine was more potent than AF-DX 116. Pirenzepine (70.8 +/- 2.8% correct) produced a greater deficit than AF-DX 116 (83.3 +/- 0.0%) at 70 micrograms, and the deficit at 10 micrograms (83.3 +/- 2.8%) was equal to that produced by 70 micrograms of AF-DX 116. The data provide additional support for the cholinergic hypothesis of memory and new information regarding the subtypes of muscarinic receptors likely to be involved in representational memory. Based on the greater susceptibility of representational memory to the effects of pirenzepine, it is suggested that M1 receptors in the hippocampus play a greater role in memory function than M2 receptors.
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Affiliation(s)
- W S Messer
- Department of Medicinal and Biological Chemistry, College of Pharmacy, University of Toledo, OH 43606
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