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Cano JC, Huang W, Fénelon K. The amygdala modulates prepulse inhibition of the auditory startle reflex through excitatory inputs to the caudal pontine reticular nucleus. BMC Biol 2021; 19:116. [PMID: 34082731 PMCID: PMC8176709 DOI: 10.1186/s12915-021-01050-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 05/12/2021] [Indexed: 01/20/2023] Open
Abstract
Background Sensorimotor gating is a fundamental pre-attentive process that is defined as the inhibition of a motor response by a sensory event. Sensorimotor gating, commonly measured using the prepulse inhibition (PPI) of the auditory startle reflex task, is impaired in patients suffering from various neurological and psychiatric disorders. PPI deficits are a hallmark of schizophrenia, and they are often associated with attention and other cognitive impairments. Although the reversal of PPI deficits in animal models is widely used in pre-clinical research for antipsychotic drug screening, the neurotransmitter systems and synaptic mechanisms underlying PPI are still not resolved, even under physiological conditions. Recent evidence ruled out the longstanding hypothesis that PPI is mediated by midbrain cholinergic inputs to the caudal pontine reticular nucleus (PnC). Instead, glutamatergic, glycinergic, and GABAergic inhibitory mechanisms are now suggested to be crucial for PPI, at the PnC level. Since amygdalar dysfunctions alter PPI and are common to pathologies displaying sensorimotor gating deficits, the present study was designed to test that direct projections to the PnC originating from the amygdala contribute to PPI. Results Using wild type and transgenic mice expressing eGFP under the control of the glycine transporter type 2 promoter (GlyT2-eGFP mice), we first employed tract-tracing, morphological reconstructions, and immunohistochemical analyses to demonstrate that the central nucleus of the amygdala (CeA) sends glutamatergic inputs lateroventrally to PnC neurons, including GlyT2+ cells. Then, we showed the contribution of the CeA-PnC excitatory synapses to PPI in vivo by demonstrating that optogenetic inhibition of this connection decreases PPI, and optogenetic activation induces partial PPI. Finally, in GlyT2-Cre mice, whole-cell recordings of GlyT2+ PnC neurons in vitro paired with optogenetic stimulation of CeA fibers, as well as photo-inhibition of GlyT2+ PnC neurons in vivo, allowed us to implicate GlyT2+ neurons in the PPI pathway. Conclusions Our results uncover a feedforward inhibitory mechanism within the brainstem startle circuit by which amygdalar glutamatergic inputs and GlyT2+ PnC neurons contribute to PPI. We are providing new insights to the clinically relevant theoretical construct of PPI, which is disrupted in various neuropsychiatric and neurological diseases. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-01050-z.
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Affiliation(s)
- Jose Carlos Cano
- Department of Biological Sciences, University of Texas at El Paso, 500 West University Avenue, El Paso, TX, 79912, USA
| | - Wanyun Huang
- Biology Department, University of Massachusetts Amherst, Life Science Laboratories, 240 Thatcher Road, Amherst, MA, 01002, USA
| | - Karine Fénelon
- Biology Department, University of Massachusetts Amherst, Life Science Laboratories, 240 Thatcher Road, Amherst, MA, 01002, USA.
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The Role of Cholinergic Midbrain Neurons in Startle and Prepulse Inhibition. J Neurosci 2018; 38:8798-8808. [PMID: 30171090 DOI: 10.1523/jneurosci.0984-18.2018] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 08/01/2018] [Accepted: 08/20/2018] [Indexed: 01/21/2023] Open
Abstract
One of the two major cholinergic centers of the mammalian brain is located in the midbrain, i.e., the pedunculopontine tegmentum (PPTg) and the adjacent laterodorsal tegmentum. These cholinergic neurons have been shown to be important for e.g., arousal, reward associations, and sleep. They also have been suggested to mediate sensorimotor gating, measured as prepulse inhibition of startle (PPI). PPI disruptions are a hallmark of schizophrenia and are observed in various other psychiatric disorders, where they are associated with, and often predictive of, other cognitive symptoms. PPI has been proposed to be mediated by a short midbrain circuitry including inhibitory cholinergic projections from PPTg to the startle pathway. Although the data indicating the involvement of the PPTg is very robust, some more recent evidence challenges that there is a cholinergic contribution to PPI. We here use transient optogenetic activation of specifically the cholinergic PPTg neurons in male and female rats to address their role in startle modulation in general, and in PPI specifically. Although we could confirm the crucial role of PPTg cholinergic neurons in associative reward learning, validating our experimental approach, we found that activation of cholinergic PPTg neurons did not inhibit startle responses. In contrast, activation of cholinergic PPTg neurons enhanced startle, which is in accordance with their general role in arousal and indicate a potential involvement in sensitization of startle. We conclude that noncholinergic PPTg neurons mediate PPI in contrast to the longstanding hypothetical view that PPI is mediated by cholinergic PPTg neurons.SIGNIFICANCE STATEMENT Activation of cholinergic neurons in the midbrain has been assumed to mediate prepulse inhibition of startle (PPI), a common measure of sensorimotor gating that is disrupted in schizophrenia and other psychiatric disorders. We here revisit this long-standing hypothesis using optogenetic activation of these specific neurons combined with startle testing in rats. In contrast to the hypothetical role of these neurons in startle modulation, we show that their activation leads to an increase of baseline startle and to prepulse facilitation. This supports recent data by others that have started to cast some doubt on the cholinergic hypothesis of PPI, and calls for a revision of the theoretical construct of PPI mechanisms.
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Tabor KM, Smith TS, Brown M, Bergeron SA, Briggman KL, Burgess HA. Presynaptic Inhibition Selectively Gates Auditory Transmission to the Brainstem Startle Circuit. Curr Biol 2018; 28:2527-2535.e8. [PMID: 30078569 DOI: 10.1016/j.cub.2018.06.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 06/11/2018] [Accepted: 06/12/2018] [Indexed: 12/25/2022]
Abstract
Filtering mechanisms prevent a continuous stream of sensory information from swamping perception, leading to diminished focal attention and cognitive processing. Mechanisms for sensory gating are commonly studied using prepulse inhibition, a paradigm that measures the regulated transmission of auditory information to the startle circuit; however, the underlying neuronal pathways are unresolved. Using large-scale calcium imaging, optogenetics, and laser ablations, we reveal a cluster of 30 morphologically identified neurons in zebrafish that suppress the transmission of auditory signals during prepulse inhibition. These neurons project to a key sensorimotor interface in the startle circuit-the termination zone of auditory afferents on the dendrite of a startle command neuron. Direct measurement of auditory nerve neurotransmitter release revealed selective presynaptic inhibition of sensory transmission to the startle circuit, sparing signaling to other brain regions. Our results provide the first cellular resolution circuit for prepulse inhibition in a vertebrate, revealing a central role for presynaptic gating of sensory information to a brainstem motor circuit.
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Affiliation(s)
- Kathryn M Tabor
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA.
| | - Trevor S Smith
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Mary Brown
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Sadie A Bergeron
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Kevin L Briggman
- Circuit Dynamics and Connectivity Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Harold A Burgess
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA.
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Bronson DR, Preuss T. Cellular Mechanisms of Cortisol-Induced Changes in Mauthner-Cell Excitability in the Startle Circuit of Goldfish. Front Neural Circuits 2017; 11:68. [PMID: 29033795 PMCID: PMC5625080 DOI: 10.3389/fncir.2017.00068] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 09/11/2017] [Indexed: 11/13/2022] Open
Abstract
Predator pressure and olfactory cues (alarm substance) have been shown to modulate Mauthner cell (M-cell) initiated startle escape responses (C-starts) in teleost fish. The regulation of such adaptive responses to potential threats is thought to involve the release of steroid hormones such as cortisol. However, the mechanism by which cortisol may regulate M-cell excitability is not known. Here, we used intrasomatic, in vivo recordings to elucidate the acute effects of cortisol on M-cell membrane properties and sound evoked post-synaptic potentials (PSPs). Cortisol tonically decreased threshold current in the M-cell within 10 min before trending towards baseline excitability over an hour later, which may indicate the involvement of non-genomic mechanisms. Consistently, current ramp injection experiments showed that cortisol increased M-cell input resistance in the depolarizing membrane, i.e., by a voltage-dependent postsynaptic mechanism. Cortisol also increases the magnitude of sound-evoked M-cell PSPs by reducing the efficacy of local feedforward inhibition (FFI). Interestingly, another pre-synaptic inhibitory network mediating prepulse inhibition (PPI) remained unaffected. Together, our results suggest that cortisol rapidly increases M-cell excitability via a post-synaptic effector mechanism, likely a chloride conductance, which, in combination with its dampening effect on FFI, will modulate information processing to reach threshold. Given the central role of the M-cell in initiating startle, these results are consistent with a role of cortisol in mediating the expression of a vital behavior.
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Affiliation(s)
- Daniel R Bronson
- The Graduate Center, City University of New York, New York, NY, United States
| | - Thomas Preuss
- Hunter College, City University of New York, New York, NY, United States
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Behavioral methods for the functional assessment of hair cells in zebrafish. Front Med 2017; 11:178-190. [PMID: 28349300 DOI: 10.1007/s11684-017-0507-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Accepted: 11/24/2016] [Indexed: 10/19/2022]
Abstract
Zebrafish is an emerging animal model for studies on auditory system. This model presents high comparability with humans, good accessibility to the hearing organ, and high throughput capacity. To better utilize this animal model, methodologies need to be used to quantify the hearing function of the zebrafish. Zebrafish displays a series of innate and robust behavior related to its auditory function. Here, we reviewed the advantage of using zebrafish in auditory research and then introduced three behavioral tests, as follows: the startle response, the vestibular-ocular reflex, and rheotaxis. These tests are discussed in terms of their physiological characteristics, up-to-date technical development, and apparatus description. Test limitation and areas to improve are also introduced. Finally, we revealed the feasibility of these applications in zebrafish behavioral assessment and their potential in the high-throughput screening on hearing-related genes and drugs.
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Ogino K, Hirata H. Defects of the Glycinergic Synapse in Zebrafish. Front Mol Neurosci 2016; 9:50. [PMID: 27445686 PMCID: PMC4925712 DOI: 10.3389/fnmol.2016.00050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 06/13/2016] [Indexed: 12/26/2022] Open
Abstract
Glycine mediates fast inhibitory synaptic transmission. Physiological importance of the glycinergic synapse is well established in the brainstem and the spinal cord. In humans, the loss of glycinergic function in the spinal cord and brainstem leads to hyperekplexia, which is characterized by an excess startle reflex to sudden acoustic or tactile stimulation. In addition, glycinergic synapses in this region are also involved in the regulation of respiration and locomotion, and in the nociceptive processing. The importance of the glycinergic synapse is conserved across vertebrate species. A teleost fish, the zebrafish, offers several advantages as a vertebrate model for research of glycinergic synapse. Mutagenesis screens in zebrafish have isolated two motor defective mutants that have pathogenic mutations in glycinergic synaptic transmission: bandoneon (beo) and shocked (sho). Beo mutants have a loss-of-function mutation of glycine receptor (GlyR) β-subunit b, alternatively, sho mutant is a glycinergic transporter 1 (GlyT1) defective mutant. These mutants are useful animal models for understanding of glycinergic synaptic transmission and for identification of novel therapeutic agents for human diseases arising from defect in glycinergic transmission, such as hyperekplexia or glycine encephalopathy. Recent advances in techniques for genome editing and for imaging and manipulating of a molecule or a physiological process make zebrafish more attractive model. In this review, we describe the glycinergic defective zebrafish mutants and the technical advances in both forward and reverse genetic approaches as well as in vivo visualization and manipulation approaches for the study of the glycinergic synapse in zebrafish.
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Affiliation(s)
- Kazutoyo Ogino
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University Sagamihara, Japan
| | - Hiromi Hirata
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University Sagamihara, Japan
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Frau R, Mosher LJ, Bini V, Pillolla G, Pes R, Saba P, Fanni S, Devoto P, Bortolato M. The neurosteroidogenic enzyme 5α-reductase modulates the role of D1 dopamine receptors in rat sensorimotor gating. Psychoneuroendocrinology 2016; 63:59-67. [PMID: 26415119 PMCID: PMC4695380 DOI: 10.1016/j.psyneuen.2015.09.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 08/21/2015] [Accepted: 09/14/2015] [Indexed: 01/26/2023]
Abstract
Neurosteroids exert diverse modulatory actions on dopamine neurotransmission and signaling. We previously documented that the enzyme 5α-reductase, which catalyzes the main rate-limiting step in neurosteroid synthesis, is required for the behavioral responses of Sprague-Dawley rats to non-selective dopaminergic agonists, such as the D1-D2 receptor agonist apomorphine. Specifically, systemic and intra-accumbal administrations of the 5α-reductase inhibitor finasteride countered apomorphine-induced deficits of sensorimotor gating, as measured by the prepulse inhibition (PPI) of the startle reflex; the classes of dopamine receptors involved in these effects, however, remain unknown. Prior rodent studies have revealed that the contributions of dopamine receptors to PPI regulation vary depending on the genetic background; thus, we analyzed the effect of finasteride on the PPI deficits induced by selective dopamine receptor agonists in Long-Evans (a strain exhibiting PPI deficits in response to both D1 and D2 receptor agonists) and Sprague-Dawley rats (which display PPI reductions following treatment with D2, and D3, but not D1 receptor agonists). In Long-Evans rats, finasteride opposed the PPI deficits induced by activation of D1, but not D2 receptors; conversely, in Sprague-Dawley rats, finasteride prevented the reductions in %PPI and accumbal dopamine extracellular levels caused by selective stimulation of D3, but not D2 receptors; however, the effects on %PPI were not confirmed by analyses on absolute PPI values. Our findings suggest that 5α-reductase modulates the effects of D1, but not D2 receptor agonists on sensorimotor gating. These data may help elucidate the role of neurosteroids in neuropsychiatric disorders featuring PPI deficits, including schizophrenia and Tourette syndrome.
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MESH Headings
- 3-Oxo-5-alpha-Steroid 4-Dehydrogenase/metabolism
- 5-alpha Reductase Inhibitors/pharmacology
- Animals
- Dopamine Agonists/pharmacology
- Finasteride/pharmacology
- Male
- Microdialysis
- Nucleus Accumbens/drug effects
- Nucleus Accumbens/metabolism
- Prepulse Inhibition/drug effects
- Prepulse Inhibition/physiology
- Rats
- Rats, Long-Evans
- Rats, Sprague-Dawley
- Receptors, Dopamine D1/drug effects
- Receptors, Dopamine D1/metabolism
- Receptors, Dopamine D2/drug effects
- Receptors, Dopamine D2/metabolism
- Receptors, Dopamine D3/drug effects
- Receptors, Dopamine D3/metabolism
- Reflex, Startle/drug effects
- Reflex, Startle/physiology
- Sensory Gating/drug effects
- Sensory Gating/physiology
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Affiliation(s)
- Roberto Frau
- "Guy Everett" Laboratory, Dept. of Biomedical Sciences, University of Cagliari, Italy; Tourette Syndrome Center, University of Cagliari, Italy
| | - Laura J Mosher
- Dept. of Pharmacology and Toxicology, University of Kansas, Lawrence, KS, USA; Consortium for Translational Research on Aggression and Drug Abuse (ConTRADA), University of Kansas, Lawrence, KS, USA; Problem Gambling Research Studies (ProGResS) Network, University of Kansas, Lawrence, KS, USA
| | - Valentina Bini
- "Guy Everett" Laboratory, Dept. of Biomedical Sciences, University of Cagliari, Italy; Tourette Syndrome Center, University of Cagliari, Italy
| | - Giuliano Pillolla
- "Guy Everett" Laboratory, Dept. of Biomedical Sciences, University of Cagliari, Italy
| | - Romina Pes
- "Guy Everett" Laboratory, Dept. of Biomedical Sciences, University of Cagliari, Italy; Dept. of Pharmacology and Toxicology, University of Kansas, Lawrence, KS, USA
| | - Pierluigi Saba
- "Guy Everett" Laboratory, Dept. of Biomedical Sciences, University of Cagliari, Italy
| | - Silvia Fanni
- "Guy Everett" Laboratory, Dept. of Biomedical Sciences, University of Cagliari, Italy
| | - Paola Devoto
- "Guy Everett" Laboratory, Dept. of Biomedical Sciences, University of Cagliari, Italy; Tourette Syndrome Center, University of Cagliari, Italy
| | - Marco Bortolato
- Tourette Syndrome Center, University of Cagliari, Italy; Dept. of Pharmacology and Toxicology, University of Kansas, Lawrence, KS, USA; Consortium for Translational Research on Aggression and Drug Abuse (ConTRADA), University of Kansas, Lawrence, KS, USA; Problem Gambling Research Studies (ProGResS) Network, University of Kansas, Lawrence, KS, USA.
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