Biomedical subjects

H Korn

Publications and source records attributed to H Korn.

At least 19 recordsLinked to original sources

PubMed2002

Further evidence for a reversed crossing of foveal projections in schizophrenic vulnerability.

Further evidence in support of the thesis developed in a previous article published in Medical Hypotheses (Sept. 2000) proposing that schizophrenic vulnerability might consist of the temporal instead of the nasal foveal projections crossing over in the chiasma opticum has been provided by an experiment in which pinholes are used to isolate foveally stimulated from peripherally stimulated vergence. By shifting the pinholes inwards or outwards a dilemma is created regarding the fusion of the edges of the two pinholes or of a single diode light seen at the inner or outer edges of the pinholes. It was revealed that schizophrenic patients never solved the dilemma in favour of what was represented on the temporal foveal halves while this was always the case in the control group. At best, the patients fusioned neither the diode light nor the pinhole edges but saw both double. An explanation is given as to how this disturbance might be based on the interchange of nasal and temporal foveal projections and might lead to the dissociation of the visual goals of the two eyes, as shown in a previous test. The cause of markers of schizophrenic vulnerability mentioned in literature, in particular saccaded SPEM, P50 response and hyperdopaminergia, is related to such an interchange and suggestions are made for further experiments. Finally, the difficulty of schizophrenic patients to distinguish between reality and illusion is attributed to a disconnection of spatial and object perception.

Accommodation, Ocular↗

PubMed2001

Activation of human alpha1 and alpha2 homomeric glycine receptors by taurine and GABA.

1. Two ligand binding alpha subunits, alpha1 and alpha2, of the human (H) glycine receptor (GlyR) are involved at inhibitory synapses in the adult and neonatal spinal cord, respectively. The ability of homomeric alphaH1 and alphaH2 GlyRs to be activated by glycine, taurine and GABA was studied in Xenopus oocytes or in the human embryonic kidney HEK-293 cell line. 2. In outside-out patches from HEK cells, glycine, taurine and GABA activated both GlyRs with the same main unitary conductance, i.e. 85 +/- 3 pS (n = 6) for alphaH1, and 95 +/- 5 pS (n = 4) for alphaH2. 3. The sensitivity of both alphaH1 and alphaH2 GlyRs to glycine was highly variable. In Xenopus oocytes the EC50 for glycine (EC50gly) was between 25 and 280 microM for alphaH1 (n = 44) and between 46 and 541 microM for alphaH2 (n = 52). For both receptors, the highest EC50gly values were found on cells with low maximal glycine responses. 4. The actions of taurine and GABA were dependent on the EC50gly: (i) their EC50 values were linearly correlated to EC50gly, with EC50tau approximately 10 EC50gly and EC50GABA approximately 500-800 EC50gly; (ii) they could act either as full or weak agonists depending on the EC50gly. 5. The Hill coefficient (n(H)) of glycine remained stable regardless of the EC50gly whereas n(H) for taurine decreased with increasing EC50tau. 6. The degree of desensitization, evaluated by fast application of saturating concentrations of agonist on outside-out patches from Xenopus oocytes, was similar for glycine and taurine on both GlyRs and did not exceed 50 %. 7. Our data concerning the variations of EC50gly and the subsequent behaviour of taurine and GABA could be qualitatively described by the simple del Castillo-Katz scheme, assuming that the agonist gating constant varies whereas the binding constants are stable. However, the stability of the Hill coefficient for glycine was not explained by this model, suggesting that other mechanisms are involved in the modulation of EC50.

Algorithms↗

PubMed2001

Slow inhibitory potentials in the teleost Mauthner cell.

In vivo recordings from Mauthner cells in adult zebrafish (Danio rerio) and goldfish (Carassius auratus) preparations with potassium chloride filled electrodes revealed a new class of long-lasting synaptic events in these cells. Their decay time constant ranged from 20 to 80ms, which is about 20 times longer than that of previously identified fast glycinergic inhibitory postsynaptic potentials in this neuron. The average time to peak of these slow events ranged from 1 to 6ms. We demonstrated that they are also inhibitory since (i) they were resistant to antagonists of the excitatory glutamatergic receptors; (ii) their amplitude was increased following chloride loading of the Mauthner cell; (iii) their reversal potential was the same as that of fast, glycinergic inhibitory postsynaptic potentials; and (iv) they produced an inhibitory shunt of the cell's membrane resistance. Furthermore, as with the fast inhibitory postsynaptic potentials, the decay time of the slow events is voltage dependent, increasing when the Mauthner cell is depolarized. However, these inhibitory postsynaptic potentials had a different pharmacological profile to the fast glycinergic ones. That is, they persisted in the presence of strychnine at doses that abolished the fast ones and they were more sensitive to bicuculline. These data are compatible with the notion that these inhibitory postsynaptic potentials are mediated by activation of a different inhibitory receptor type, and may be GABAergic. In addition, the decay time constant of the fast inhibitory postsynaptic current was shorter than the first of the two components that contribute to the bi-exponential decay reported previously for miniature inhibitory postsynaptic currents in Mauthner cells of larval zebrafish. This suggests developmental modifications and/or a switch in the assembly of glycine receptor subtypes. While amplitude distributions of the fast miniature inhibitory postsynaptic potentials recorded in the presence of tetrodotoxin generally could fit with a single Gaussian function, the amplitude histograms of slow miniature events were skewed, often with multiple nearly equally spaced peaks, consistent with the synchronous release of several quantal units. These previously undescribed slow unitary inhibitory postsynaptic potentials contribute to inhibitory synaptic noise recorded in the Mauthner cells. Specifically, autocorrelation analysis revealed gamma-like rhythms (30-80Hz) in each of two phases, characterized as "noisy" and "quiet", and dominated by the fast and slow inhibitory postsynaptic potentials, respectively. The major frequencies of these two states were significantly different (i.e. around 90 and 40Hz, respectively), suggesting that the fast and slow inhibitory postsynaptic potentials are derived from different inhibitory networks. Chloride-filled Mauthner cells gradually hyperpolarized in the presence of tetrodotoxin, reflecting the effect of ongoing activity in the interneurons that produce the slow events. We conclude that this new class of inhibitory postsynaptic potentials contributes to the tonic inhibition which controls the Mauthner cell's excitability. In physiological conditions, this regulatory influence is expressed as a continuous shunt of this neuron's input resistance and responsiveness to sensory inputs.

2-Amino-5-phosphonovalerate↗

PubMed2001

Isolation and characterization of an alpha 2-type zebrafish glycine receptor subunit.

The complementary DNA for a novel alpha subunit of the glycine receptor, alphaZ2, was isolated from a zebrafish adult brain library. The molecular characteristics, phylogenetic relationships and messenger RNA length of this alphaZ2 subunit show it to be an alpha2-type glycine receptor subunit isoform. The leader peptide however, diverges from those of known glycine receptor alpha isoforms. Recombinantly expressed in Xenopus oocytes, alphaZ2 formed functional glycine receptor channels. These homomeric channels were activated by glycine and taurine, with apparent affinities similar to those reported for zebrafish alphaZ1 glycine receptor, and were also effectively antagonized by nanomolar concentrations of strychnine. However, during prolonged applications of agonists, ionic currents of alphaZ2 receptor channels declined to a much lower steady-state level than those of alphaZ1, indicating different desensitization properties. Analysis of messenger RNA revealed that alphaZ2 is specifically expressed in adult brain tissue and present in both adult and embryonic zebrafish. This report contributes to the characterization of the diversity of glycine receptor isoforms in vertebrates.

Aging↗

PubMed2001

Regional distribution of glycine receptor messenger RNA in the central nervous system of zebrafish.

We report the cloning of the zebrafish beta subunit of the glycine receptor and compare the anatomical distribution of three glycine receptor subunit constituents in adult zebrafish brain (alphaZ1, alphaZ2 and betaZ) to the expression pattern of homologous receptor subunits (alpha1, alpha2 and beta) in the mammalian adult CNS. Non-radioactive hybridization was used to map the distribution of the alphaZ1, alphaZ2 and betaZ glycine receptor subunit messenger RNAs in the adult zebrafish brain. The anterior-posterior expression gradient found in adult zebrafish brain was similar to that reported in mammalian CNS. However, the glycine receptor transcripts, notably the alphaZ1 subunit, were more widely distributed in the anterior regions of the zebrafish than in the adult mammalian brain. The isoform-specific distribution pattern was less regionalized in zebrafish than in the rat mammalian CNS. Nevertheless, there was some regionalization of alphaZ1, alphaZ2 and betaZ transcripts in the diencephalic and mesencephalic nuclei where different sensory and motor centers express either alphaZ1/betaZ or alphaZ2 subunits. In contrast to the widespread distribution of the beta subunit in adult mammalian brain, alphaZ2 messenger RNA presented the widest expression territory of all three glycine receptor subunits tested. alphaZ2 messenger RNA was expressed in the absence of alphaZ1 and betaZ messenger RNA in the outer nuclear layer of the retina, the inferior olive and the raphe of the medulla oblongata, as well as in the nucleus of Cajal of the medulla spinalis. In contrast, an identified central neuron of the reticular formation, the Mauthner cell, expresses all three glycine receptor subunits (alphaZ1, alphaZ2 and betaZ). This report extends the already described glycine receptor expression in the vertebrate CNS and confirms the importance of glycine-mediated inhibition in spinal cord and brainstem.

Amino Acid Sequence↗

PubMed2001

Is there chaos in the brain? I. Concepts of nonlinear dynamics and methods of investigation.

In the light of results obtained during the last two decades in a number of laboratories, it appears that some of the tools of nonlinear dynamics, first developed and improved for the physical sciences and engineering, are well-suited for studies of biological phenomena. In particular it has become clear that the different regimes of activities undergone by nerve cells, neural assemblies and behavioural patterns, the linkage between them, and their modifications over time, cannot be fully understood in the context of even integrative physiology, without using these new techniques. This report, which is the first of two related papers, is aimed at introducing the non expert to the fundamental aspects of nonlinear dynamics, the most spectacular aspect of which is chaos theory. After a general history and definition of chaos the principles of analysis of time series in phase space and the general properties of chaotic trajectories will be described as will be the classical measures which allow a process to be classified as chaotic in ideal systems and models. We will then proceed to show how these methods need to be adapted for handling experimental time series; the dangers and pitfalls faced when dealing with non stationary and often noisy data will be stressed, and specific criteria for suspecting determinism in neuronal cells and/or assemblies will be described. We will finally address two fundamental questions, namely i) whether and how can one distinguish, deterministic patterns from stochastic ones, and, ii) what is the advantage of chaos over randomness: we will explain why and how the former can be controlled whereas, notoriously, the latter cannot be tamed. In the second paper of the series, results obtained at the level of single cells and their membrane conductances in real neuronal networks and in the study of higher brain functions, will be critically reviewed. It will be shown that the tools of nonlinear dynamics can be irreplaceable for revealing hidden mechanisms subserving, for example, neuronal synchronization and periodic oscillations. The benefits for the brain of adopting chaotic regimes with their wide range of potential behaviours and their aptitude to quickly react to changing conditions will also be considered.

Animals↗

PubMed2000

Characterization of the two zebrafish orthologues of the KAL-1 gene underlying X chromosome-linked Kallmann syndrome.

The gene underlying X chromosome-linked Kallmann syndrome, KAL-1, has been identified for several years, yet its role in development is still poorly understood. In order to take advantage of the zebrafish as a model in developmental genetics, we isolated the two KAL-1 orthologues, kal1.1 and kal1.2, in this species. Comparison of deduced protein sequences with the human one shows 75.5 and 66.5% overall homology, respectively. The most conserved domains are the whey acidic protein-like domain and the first of four fibronectin-like type III repeats. However, kal1.2 putative protein lacks the basic C-terminal domain (20 residues) found in kal1.1 and KAL-1. The expressions of kal1.1 and kal1.2 were studied in the embryo between 6 and 96 hours post fertilization using whole-mount in situ hybridization. Although a few structures express both genes, kal1.1 and kal1.2 expression patterns are largely non-overlapping. Taken together, these patterns match fairly well those previously reported for human KAL-1 and chicken kal1. As regards the olfactory system, kal1.1 is expressed, from 37 h.p.f. onward, in the presumptive olfactory bulbs, whereas kal1.2 transcript is only detected, from 48 h.p.f., in the epithelium of the nasal cavity. The relevance of the zebrafish as an animal model for studying both the function of KAL-1 in normal development and the developmental failure leading to the olfactory defect in Kallmann syndrome, is discussed.

Amino Acid Sequence↗

PubMed2000

Calcium mobilization elicited by two types of nicotinic acetylcholine receptors in mouse substantia nigra pars compacta.

Nicotinic acetylcholine receptors (nAChRs) are expressed in the midbrain ascending dopaminergic system, a target of many addictive drugs. Here we assessed the intracellular Ca2+ level by imaging fura-2-loaded cells in substantia nigra pars compacta in mouse brain slices, and we examined the influence on this level of prolonged exposures to nicotine using mice lacking the nAChR beta2-subunit. In control cells, superfusion with nicotine (10-100 microM) caused a long-lasting rise of intracellular Ca2+ level which depended on extracellular Ca2+. This nicotinic response was almost completely absent in beta2-/- mutant mice, leaving a small residual response to a high concentration (100 microM) of nicotine which was inhibited by the alpha7-subunit-selective antagonist, methyllycaconitine. Conversely, the alpha7-subunit-selective agonist choline (10 mM) caused a methyllycaconitine-sensitive increase in intracellular Ca2+ level both in wild-type and beta2-/- mutant mice. Nicotine-elicited Ca2+ mobilization was reduced by the Na+ channel blocker tetrodotoxin (TTX) and by T-type Ca2+ channel blocking agents, whereas the choline-elicited Ca2+ increase was insensitive to TTX. Neither nicotine nor choline produced Ca2+ increase following inhibition of the release of Ca2+ from intracellular stores by dantrolene. These results demonstrate that in nigral dopaminergic neurons, nicotine can elicit Ca2+ mobilization via activation of two distinct nAChR subtypes: that of beta2-subunit-containing nAChR followed by activation of Na+ channel and T-type Ca2+ channels, and/or activation of alpha7-subunit-containing nAChR. The Ca2+ influx due to nAChR activation is subsequently amplified by the recruitment of intracellular Ca2+ stores. This Ca2+ mobilization may possibly contribute to the long-term effects of nicotine on the dopaminergic system.

2-Amino-5-phosphonovalerate↗

PubMed2000

Schizophrenic vulnerability: a deficiency of the correlation between foveal perception and oculomotor proprioception?

In a previous paper published in Medical Hypotheses, the author proved by a simple mirror test a dissociation between the goals of selective attention and bifoveal fixation in a schizophrenic patient. In the present article, she enters into the details of the patient's results in ophthalmological tests which revealed an opposite deviation of accommodation and vergence, compensated in a way incompatible with Hering's law. She expounds that Hering's law is based on the correlation of retinal data with proprioceptive information of the exterior eye-muscles, and that schizophrenic vulnerability might consist of a disturbance of this correlation favouring fusion of patterns in the remote and external space over fusion in the near and central space. Some phenomena found in schizophrenic patients and their carrier parents are explained in the light of this hypothesis. Finally, the author gives detailed advice on how to overcome difficulties in the correction of the ophthalmological deviations that induce the vulnerability to take effect. ¿

Fovea Centralis↗

PubMed2000

Synaptic efficacy and the transmission of complex firing patterns between neurons.

In central neurons, the summation of inputs from presynaptic cells combined with the unreliability of synaptic transmission produces incessant variations of the membrane potential termed synaptic noise (SN). These fluctuations, which depend on both the unpredictable timing of afferent activities and quantal variations of postsynaptic potentials, have defied conventional analysis. We show here that, when applied to SN recorded from the Mauthner (M) cell of teleosts, a simple method of nonlinear analysis reveals previously undetected features of this signal including hidden periodic components. The phase relationship between these components is compatible with the notion that the temporal organization of events comprising this noise is deterministic rather than random and that it is generated by presynaptic interneurons behaving as coupled periodic oscillators. Furthermore a model of the presynaptic network shows how SN is shaped both by activities in incoming inputs and by the distribution of their synaptic weights expressed as mean quantal contents of the activated synapses. In confirmation we found experimentally that long-term tetanic potentiation (LTP), which selectively increases some of these synaptic weights, permits oscillating temporal patterns to be transmitted more effectively to the postsynaptic cell. Thus the probabilistic nature of transmitter release, which governs the strength of synapses, may be critical for the transfer of complex timing information within neuronal assemblies.

Animals↗

PubMed1999

Tonic inhibition alternates in paired neurons that set direction of fish escape reaction.

Crossed antagonism between activities in neurons subserving alternating movements such as swimming or walking has been described in a number of systems. The role of reciprocal inhibition has been implicated in these activities, but involvement of rhythmic ongoing fluctuations of membrane potential, called synaptic "noise," has not been examined. In the Mauthner (M) cells, which control the direction of escape, this activity is inhibitory. We report that in the zebrafish (Danio rerio), inhibitory synaptic noise exhibits prolonged bursts of rhythmic, inhibitory postsynaptic potentials, which attenuate the M cell's sensibility to excitatory sensory drives. Furthermore, paired intracellular recordings have shown that inhibitory synaptic noise alternates between two distinct states, noisy and quiet, which are out of phase in the two cells. Firing of either M cell resets this pattern by reducing the inhibition in the contralateral one. This suggests that an avoidance reflex in one direction may favor initiation, by the opposite M cell, of a subsequent escape toward a more appropriate location.

Action Potentials↗

PubMed1999

A statistical method for correcting distortions of amplitude distribution histograms due to collisions of synaptic events.

The waveform of spontaneous synaptic potentials or currents comprising synaptic noise can be significantly distorted when these events are closely spaced due to a high frequency activity in the presynaptic inputs that generate them. It is essential to correct these alterations prior to measurements of overlapping miniature and/or postsynaptic potentials, in order to provide reliable information about their true amplitude distributions, and to avoid spurious peaks in the resulting histograms. In this paper we describe a statistical method for making these corrections, its range of application, and its theoretical background. Its use becomes necessary when the frequency of events is of the order of 8-50 Hz, depending upon their time to peak, which ranges from 6 to 1 ms in most synaptic potentials recorded in the central nervous system.

Action Potentials↗

PubMed1999

Comparison of glycine and GABA actions on the zebrafish homomeric glycine receptor.

1. Glycine and GABA can be co-released from the same presynaptic terminals and in lower vertebrates they can activate the same glycine receptors (GlyRs). Thus we examined the effects of these two inhibitory transmitters on the homomeric GlyRs formed by the alphaZ1 subunit, of the zebrafish using two expression systems: Xenopus oocytes and the human BOSC 23 cell line. 2. The apparent affinity (EC50) of alphaZ1 for these neurotransmitters was highly variable. In Xenopus oocytes the EC50 ranged from 37 to 360 microM (mean +/- s. d. EC50 116 +/- 75 microM, n = 83) for glycine and from 8 to 120 mM (mean EC50 40 +/- 30 mM, n = 37) for GABA. 3. In BOSC cells the EC50 varied from 9 to 92 microM (mean EC50 33 +/- 17 microM, n = 19) and from 0.7 to 19.1 mM (mean EC50 4.9 +/- 4.7 mM, n = 29) for glycine and GABA, respectively. 4. GABA activated alphaZ1 GlyRs either as a weak or full agonist: its efficacy (defined as Imax,GABA/Imax,Gly) was related to EC50 by an exponential relationship. A linear relationship was observed between EC50 values for GABA and glycine. 5. In outside-out patches, GABA and glycine activated alphaZ1 with identical single-channel conductances (85-100 pS), but with different kinetics and marked effect of concentration on burst duration for glycine only. 6. In outside-out patches deactivation time constants were concentration dependent for glycine, but not for GABA. 7. Our data demonstrate that the kinetics of glycine and GABA interactions with alphaZ1 are different and that they determine the properties of these neurotransmitter actions on the GlyR.

Animals↗

PubMed1999

Functional integrity of green fluorescent protein conjugated glycine receptor channels.

The alpha subunit (alphaZ1) of the zebrafish glycine receptor (GlyR) has been N-terminus fused with green fluorescent protein (GFP). We found that both pharmacological and electrophysiological properties of this chimeric alphaZ1-GFP are indistinguishable from those of the wild-type receptor when expressed in Xenopus oocytes and cell lines. The apparent affinities of this receptor for agonists (glycine, taurine and GABA), and the antagonist (strychnine) are unchanged, and single channel kinetics are not altered. In the same expression systems, alphaZ1-GFP was visualized using fluorescence microscopy. Fluorescence was distributed anisotropically across cellular membranes. In addition to the Golgi apparatus and endoplasmic reticulum, its presence was also detected on the plasmalemma, localized at discrete hot-spots which were identified as sites of high membrane turnover. Overall, the preservation in alphaZ1-GFPs of the wild type receptor functional properties makes it a promising new tool for further in situ investigations of GlyR expression, distribution and function.

Animals↗

PubMed1999

Cloning, expression and electrophysiological characterization of glycine receptor alpha subunit from zebrafish.

The glycine receptor is a ligand-gated anion channel protein, providing inhibitory drive within the nervous system. We report here the isolation and functional characterization of a novel alpha subunit (alphaZ1) of the glycine receptor from adult zebrafish (Danio rerio) brain. The predicted amino acid sequence is 86%, 81% and 77% identical to mammalian isoforms alpha1, alpha3 and alpha2, respectively. AlphaZ1 exhibits many of the molecular features of mammalian alpha1, but the sequence patterns in the M4 and C-terminal domains are more similar to alpha2/alpha3. Phylogenetic analysis indicates that alphaZ1 is more closely related to the mammalian alpha1 subunits, being positioned, however, on a distinct branch. The alphaZ1 messenger RNA is 9.5 kb, similar to that described previously for alpha1 messenger RNAs. When expressed in Xenopus oocytes or a human cell line (BOSC 23), alphaZ1 forms a homomeric receptor which is activated by glycine and antagonized by strychnine. This receptor demonstrates unexpectedly high sensitivity to taurine and can also be activated by GABA. These results are consistent with physiological findings in lamprey and goldfish, and they suggest that this teleost fish glycine receptor displays a lower selectivity to neurotransmitters than that reported for glycine mammalian receptors.

Amino Acid Sequence↗

PubMed1999

The somatic component of schizophrenia: a dissociation of the goals of visual attention and bifoveal fixation?

The presence of disorders of eye movements is today regarded as 'the strongest candidate for a genetically transmitted biological trait marker of schizophrenic disorders' (1). The present study is based on the experience, rather than the behaviour, of one patient in a search for a method of objectifying his visual problems. This method was found to be a simple test, which demonstrates a disturbance of fixation: while one eye accommodated on the figure without vergence, the other, vergent, eye fused with the image of the related background. The disorder had been misdiagnosed as 'exophoria' in conventional ophthalmological examinations, because prevailing ophthalmological theory accepts only one mode of vision; according to the most recent researches, however, it is necessary to distinguish two complementary modes of vision--one for panorama and one for detail--which differ in their coordination of vergence and accommodation. This new bimodal theory of vision--presented here for the first time--made it possible to understand the cause of the disorder as a substitution of sighting for fixation, due either to a disinhibition of panorama vision during fixation vision, or to an interchange of ipsilateral temporal and contralateral nasal projections from the retina, both associated with a fixation disparity. After correction of the patient's fixation disparity according to an unusual method, the dissociation of the visual goals was remedied and the mental disturbances of the patient vanished.

Attention↗

PubMed1999

The biographical component of schizophrenia: a two-faced definition of relationship?

The schizophrenic's disturbed relationship with reality is generally ascribed to a mental illness of endogenous origin. Following the author's paper on a fixation disorder (1) provable in these patients, she expounds that their disturbed relationship with reality does not primarily concern their consciousness of objective reality but of their own self. As a result of contradictory definitions of relationship within his group (2,3) the schizophrenic is unable to integrate the awareness of his potentialities with the awareness of his social role. He cannot protect himself against a joker role imposed on him since his fixation disorder acts like a one-way valve impeding him from taking an active part in the definition of relationship. A hypothesis is presented as to how the schizophrenic's described fixation disorder may cause this one-way functioning of the definition of relationship.

Humans↗

PubMed1998

Inhibitory long-term potentiation underlies auditory conditioning of goldfish escape behaviour.

Long-term potentiation (LTP), the increase in synaptic strength evoked by high-frequency stimulation, is often considered to be a cellular model for learning and memory. The validity of this model depends on the assumptions that physiological stimuli can induce LTP in vivo and that the resulting synaptic modifications correlate with behavioural changes. However, modifiable synapses are generally embedded deep in complex circuits. In contrast, the goldfish Mauthner (M)-cell and its afferent synapses are easily accessible for electrophysiological studies, and firing of this neuron is sufficient to trigger fast escape behaviour in response to sudden stimuli. We have previously shown that tetanic stimulation can induce LTP of the feedforward inhibitory synapses that control the excitability of the M-cell. Here we report that natural sensory stimulation can induce potentiation of this inhibitory connection that resembles the LTP induced by afferent tetanization. Furthermore, comparable acoustic stimulation produced a parallel decrease in the probability of the sound-evoked escape reflex. Thus we demonstrate for the first time, to our knowledge, a behavioural role for the long-term synaptic strengthening of inhibitory synapses.

Acoustic Stimulation↗