Autoradiographic localization of binding sites for [3H]gamma-aminobutyrate, [3H]muscimol,(+)[3H]bicuculline methiodide and [3H] flunitrazepam in cultures of rat cerebellum and spinal cord

Cultures of rat cerebellum and spinal cord were used to visualize binding sites for [³Hγaminobutyrate, [³Hmuscimol, [³Hbicuculline methiodide and [³Hflunitrazepam by autoradiography. In cerebellar cultures, many large neurons (presumably Purkinje cells) and interneurons were labelled. In spinal cord cultures, these compounds were mainly bound to small and medium-sized neurons, whereas the majority of large neurons were unlabelled. No binding sites for these radioligands were found on glial cells. Binding of [³Hγ-aminobutyrate, [³Hmuscimol and [³Hbicuculline methiodide was markedly reduced or inhibited by adding unlabelled γ-aminobutyrate, muscimol and bicuculline (10^?3m) respectively to the incubation medium. Addition of a thienobenzazepine markedly reduced binding with [³Hflunitrazepam.It is concluded that tissue cultures are an excellent tool to visualize the cellular localization of binding sites for neurotransmitters and drugs using autoradiography.     

Septal driving of hippocampal theta rhythm: role of gamma-aminobutyrate-benzodiazepine receptor complex in mediating effects of anxiolytics

In free-moving male rats, when the hippocampal theta rhythm is artificially driven by stimulation in the septum at frequencies between 5 and 10 Hz, the function relating frequency to the threshold current required to drive the theta rhythm has a minimum at 7.7 Hz. This minimum is eliminated by anxiolytic drugs. Dose-response curves for this effect are reported for chlordiazepoxide, diazepam and meprobamate. The effect of meprobamate was reversed by two gamma-aminobutyrateA antagonists, picrotoxin and bicuculline, which have previously been shown to be without effects of their own. The gamma-aminobutyrateB agonist, baclofen, also without effect on its own, blocked the elimination of the 7.7-Hz minimum caused by the gamma-aminobutyrateA agonist, muscimol. The beta-carboline, ethyl-beta-carboline-3-carboxylate, had mixed agonist/antagonist properties, blocking the effects of chlordiazepoxide, diazepam and muscimol (though not sodium amylobarbitone) but itself acting like a benzodiazepine. Coupled with earlier data, these findings support a role for gamma-aminobutyrate receptors in mediating the effects of anxiolytic drugs.     

Naloxone excites nociceptive units in the lumbar dorsal horn of the spinal cat

Intravenous doses of 0.05–0.15 mg/kg of naloxone caused an increase in the spontaneous discharge rate of single dorsal horn units in lumbar spinal segments 5–7 in the spinal cat. This effect was seen with all of 21 units responding to noxious cutaneous stimulation. In contrast, the 7 units classified as non-nociceptive cutaneous were all unaffected by naloxone, even at doses of 0.4 mg/kg. Of two proprioceptive units, one was excited by naloxone. Naloxone also increased the response of nociceptive units to noxious radiant heat applied to the skin. Section of the ipsilateral dorsal roots of segments L₄-S₁ failed to abolish the excitatory effect of naloxone on the spontaneous activity of nociceptive units. Responses to naloxone were observed in laminae I, IV, V and VI.These results suggest that the effects of naloxone are not general and that nociceptive units in particular are excited. They also demonstrate that this effect occurs within the central nervous system and that its action is at the spinal level. It is suggested that the algesic effects of naloxone reported by others may be due, at least in part, to this action of naloxone in the spinal cord. While the results of this study support an hypothesis that an endogenous opioid agonist is being released continuously, and it is the prevention of the action of this endogenous substance on ‘opiate receptors’ at the spinal level which is observed as an excitation, it is also possible that naloxone may have an action at the spinal level independently of the actions of another agent, and that perhaps this action is on non-opiate receptors. A third possibility, raised from other recent work, is that the excitatory effects of naloxone may have been due to an antagonism of the effects of γ-aminobutyrate in the spinal cord.     

Release of D-[3H]aspartate from the dorsolateral septum after electrical stimulation of the fimbria in vitro

A new in vitro preparation from guinea-pig brain is described. The preparation consists of a slice of dorsolateral septum with adhering fimbria. The viability of the preparation was demonstrated. Fibre volleys, single and multiple unit discharges and evoked postsynaptic field potentials could be detected essentially as in vivo. Electrical stimulation of the CA3 hippocampal-septal excitatory connections through the fimbria releasedd-[³H]aspartate, as a marker forl-glutamate, from the dorsolateral septum. The release was specific. The presence of presynaptic fibre volleys at both high (1.5 mm) and low (0.1 mm) concentrations of Ca²⁺, but efflux ofd-[³H]aspartate only at high Ca²⁺ concentrations strongly favour a transmitter-related release.The results strongly suggest that two axon collaterals from the same hippocampal CA3 pyramidal cells usel-glutamate as neurotransmitter.     

The role of the γ-aminobutyrate system in the interactions of cortical evoked potentials

The interactions between acoustic and somatosensory evoked potentials were examined in the anterior suprasylvian gyrus of the cat. Under conditions of barbiturate anaesthesia, occlusion was the dominant form of interaction. γ-Aminobutyrate in local and intravenous application, and baclofen and diazepam in intravenous application significantly deepened the occlusion. γ-Aminobutyrate antagonists, picrotoxin and bicuculline, in subconvulsive doses decreased occlusion or turned it into facilitation. γ-Aminobutyrate agonists and γ-aminobutyrate depressed and γ-aminobutyrate antagonists enhanced the amplitude of the evoked potentials but the interactions by themselves proved independent from the absolute amplitudes.The interactions between evoked potentials of different modalities in the association cortex of the cat can be regarded as an expression of the actual equilibrium between excitatory and inhibitory interneuronal systems.     

Calcium-dependent release of putative neurotransmitters in the chick visual system.

The calcium-dependent release of putative neurotransmitters has been studied in the chick brain. Several radioactive compounds were taken up into chick optic lobe homogenates by a high-affinity sodium-dependent transport mechanism. At a concentration of potassium sufficient to cause extensive depolarization, a large proportion of the efflux of the accumulated labeled compounds was calcium dependent. Calcium-stimulated release was antagonized by magnesium. The calcium ionophore, A-23187, enabled calcium-related release to occur in the absence of depolarizing conditions, except after accumulation of [³H]choline. Veratridine was used in order to bring about depolarization in low external potassium concentrations. In this case magnesium was able to replace calcium in inducing the efflux of labeled compounds. Tetrodotoxin inhibited the veratridine-stimulated release of compounds in the presence of calcium. The rate of release of accumulated leucine was affected to a much lesser extent by the presence of calcium. Calcium-stimulated release was also found in homogenates of the optic nerve, indicating that this process is not confined to synapses. Calcium-stimulated release of different compounds varied according to the developmental age and temperature of incubation. This suggests that some dissimilarities in the nature of their release mechanisms exist.Our results suggest that much calcium-dependent efflux is related to presynaptic neurotransmitter release mechanisms. However, a similar release process may exist in non-synaptic regions of the neuron and in glia. Furthermore, the release of non-transmitter compounds under depolarizing conditions can also be enhanced by the presence of calcium.     

Comparative study of the release of glutamate and GABA, newly synthesized from glutamine, in various regions of the central nervous system

The in vitro release of [³H]glutamate and [³H]γ-aminobutyric acid, both newly synthesized from [³H]glutamine, were studied in various regions of the rat and pigeon brain. The amount of transmitter released from slices during stimulation by excess K⁺, as well as the ratio of the amounts of glutamate and γ-aminobutyrate released, varied considerably from region to region. Very high levels of release of glutamate were observed in rat striatum and in rat and pigeon hippocampus whereas only moderate release of glutamate was found in rat and pigeon cerebellum, rat cochlear nucleus and rat substantia nigra. The highest levels of release of γ-aminobutyrate were observed in the rat substantia nigra, hippocampus and striatum. Particularly low levels of release of glutamate was observed in the pigeon optic tectum. The release of γ-aminobutyrate and glutamate in all structures was largely calciumdependent.These results suggest that the release of glutamate and γ-aminobutyrate newly synthesized from glutamine reflects the neurotransmitter function of the two amino acids within various CNS regions. They further suggest that the glutamate synthesizing and releasing pool is different from the γ-aminobutyrate synthesizing and releasing pool. The similarity between the release of glutamate in rat and pigeon cerebellum and hippocampus suggest some structural homology in both species.     

Biochemical evidence for glutamate as a transmitter in hippocampal efferents to the basal forebrain and hypothalamus in the rat brain

The effects of bilateral transection of the fornix bundle on the high affinity uptake of glutamate and on the amino acid content in several nuclei of rat forebrain and hypothalamus were studied in order to investigate the possible role of glutamate as a transmitter of these fibres. This lesion decreased the high affinity uptake ofl-glutamate by 60–70% in the mammillary body and lateral septum, and by 40–50% in the anterior diagonal band nucleus, the bed nucleus of the stria terminalis, the mediobasal hypothalamus and the nucleus accumbens. The content of endogenous glutamate in samples dissected from freeze-dried tissue also decreased significantly in these regions. Endogenous aspartate was slightly decreased in the anterior diagonal band nucleus and the mammillary body, but unchanged in the other regions. No significant changes were seen in the levels of serine, γ-aminobutyric acid, glutamine and taurine, except for an increase in glutamine and taurine in the bed nucleus of the stria terminalis. The high affinity uptake of γ-aminobutyric acid, tested in the bed nucleus of the stria terminalis, the mediobasal hypothalamus and the mammillary body, was unchanged after the lesion.The results indicate that allocortical efferents innervating subcortical nuclei through the fornix might use glutamate as a transmitter. The study further supports the concept that glutamate plays an important role as transmitter of several different corticofugal fibre systems in mammalian brain.     

Microanatomy of enkephalin-containing neurones in the developing rat spinal cordin vitro

Enkephalin has been demonstrated in neurones in organotypic cultures of embryonic rat lumbar spinal cord using the indirect immunofluorescence technique. The peptide was demonstrated in neurone precursors in cultures of spinal cord at stage 16 (10 days' gestation). The subsequent development of the cells was studied by culturing spinal cord tissue from stage 30–34 (14–17 days' gestation) embryos and applying sequential immunocytochemistry, silver impregnation histology and autoradiography to the preparations. Acetylcholinesterase and γ-aminobutyrate transaminase activity in neurones and fibres in stage 30–34 cultures was at a maximum three weeks after explantation. Following a 24 h pulse of [³H]thymidine, about one third of enkephalin-immunoreactive neurones were labelled in cultures 7 days old. The proportion fell to nearly zero in cultures 14 and 21 days old. At this time axonal and dendritic growth began in most immunoreactive cells. The disappearance of neuritic growth cones indicated that differentiation of the cells was not complete until 5–7 weeks after explanation. Fully-differentiated neurones had cell bodies of 10–15 μm diameter and processes spanning 400 μm or less. During development and at maturity, three groups of immunoreactive neurone were identified by morphological criteria. Immunocytochemical demonstration of leucine enkephalin-containing neurones in smear preparations of spinal cord from young animals suggested that their cytodifferentiation was also completed late in the process of development in vivo (after the second week of life).The results show that lumbar spinal neurones containing the putative transmitter, leucine enkephalin, have a prolonged but otherwise normal pattern of development when grown in tissue culture. When mature they appear to be small interneurones of several morphological types.     

Cellular localization of the uptake of [3H]taurine and [3H]β-alanine in cultures of the rat central nervous system

The cellular localization of the uptake of [³H]taurine and [³H]β-alanine was studied in cultures of rat central nervous system using autoradiography. In brain stem and spinal cord cultures, both amino acids were taken up by neurones and glial cells. In cerebellar cultures, [³H]taurine was accumulated by all glial cells and by a small number of neurones, whereas [³H]β-alanine was only taken up by glial elements. The uptake of both amino acids was sodium and temperature dependent, indicating an active transport mechanism.The results provide further support for the hypothesis that taurine and β-alanine are neurotransmitters in the mammalian central nervous system.     

Effects of topical baclofen on C fibre-evoked neuronal activity in the rat dorsal horn

Baclofen appears to be an agonist for the bicuculline-insensitive gamma-aminobutyrateB receptors associated with C fibre terminals in the dorsal horn of the spinal cord. We have tested the effect of baclofen (applied intrathecally onto the spinal cord) on the A and C fibre-evoked responses of convergent/multireceptive neurones in the halothane-anaesthetized rat. L-Baclofen produced a dose-dependent inhibition of the C fibre- and pinch-evoked activity of these neurones which persisted for 2 h whilst the A fibre and tactile activities were little changed. The C fibre-evoked (X 3 threshold) responses were markedly or completely inhibited 10 min after doses of between 0.25 and 30 micrograms of L-baclofen (n = 21) with 0.05 micrograms causing a 48% (n = 3) and 0.01 micrograms a 28% inhibition (n = 3). D-Baclofen (30 micrograms), the inactive isomer, produced no significant changes in activity (n = 10). Bicuculline (60 micrograms) applied intrathecally before (n = 7) or after (n = 8) L-baclofen did not reverse the inhibitions. Intravenous baclofen (1-3 mg/kg) also produced neuronal inhibitions similar to the effects of intrathecal injection. The results suggest that gamma-aminobutyrateB receptors may exert a presynaptic control of C fibre afferents in the dorsal horn following intrathecal administration in the rat.     

K+-stimulated release of labeled γ-aminobutyrate,glycine and taurine in slices of several regions of rat central nervous system

The effect of depolarization by high K⁺ concentration (68.5 mm) on the release of [³H] γ-aminobutyrate (GABA), [¹⁴C]glycine and [³⁵S]taurine was studied in superfused slices of rat cerebellum, striatum, hypothalamus, colliculi, cerebral cortex and ventral and dorsal halves of spinal cord. The release of [³H]GABA was notably stimulated by K⁺-depolarization in all regions studied, particularly in the cerebral cortex and the hypothalamus. The Ca²⁺-dependence of this phenomenon was studied in the cortex and ventral spinal cord; in both regions the K⁺-stimulated release was abolished when Ca²⁺ was omitted from the superfusing medium. The release of [¹⁴C]glycine was also stimulated in all regions, except the cerebellum, but to a lesser extent than that of GABA. This stimulation was Ca²⁺-dependent in the ventral spinal cord but not in the cerebral cortex. The release of [³⁵S]taurine was not affected by K⁺-depolarization in any of the regions studied.These results are consistent with a widely distributed neurotransmitter role for GABA. The Ca²⁺-dependence of glycine release in the spinal cord is in agreement with a role of this amino acid as a transmitter in this region. The finding that [³⁵S]taurine release was not stimulated by K⁺-depolarization in any of the regions studied, under experimental conditions identical to those resulting in an enhancement of [³H]GABA and [¹⁴C]glycine release, argues against a neurotransmitter role of this amino acid in brain and spinal cord.     

Levamisole-resitant mutants of the nematode Caenorhabditis elegans appear to lack pharmacological acetylcholine receptors

The body muscles of the nematode Caenorhabditis elegans contract when the animal is cut in solutions of cholinergic agonists. The pharmacological specificity of the apparent nematode cholinergic receptor is most like a vertebrate nicotink ganglionic receptor. The anthelmintic levamisole resembles nicotine in its effects and acts directly or indirectly as both a cholinergic agonist and antagonist. Mutants at 7 loci conferring extreme resistance to levamisole respond very poorly to cholinergic agonists effective on the wild type. These mutants all share the same uncoordinated motor behavior and contract like the wild type in response to the noncholinergic muscle agonist ouabain. The uncoordinated motor behavior of the mutants and the resistance to levamisole and cholinergic agonists can be copied by exposing the wild type to the cholinergic blocking agent mecamylamine. Another class of mutants (8 loci, 5 corresponding to loci also producing extremely resistant alleles) possesses intermediate resistance to levamisole and cholinergic agonists and behaves pharmacologically and genetically like mutants moderately impaired in the levamisole-sensitive function. A third class of mutants (2 loci) with spasmodic muscle twitching is partially resistant to cholinergic agonists and to ouabain and probably represents defects in the muscle-contraction cycle physiologically downstream from the levamisole-sensitive function. Meta-phenyl-substituted derivatives of levamisole retain considerable biological activity and may be useful in the molecular analysis of our mutants. α-bungarotoxin, benzyltrimethyl-ammonium, and 3-quinuclidinyl benzilate, potential probes of cholinergic receptor function, do not show significant activity in our cut worm assay.The nature of the observed cholinergic response and the neuronanatomy of C. elegans suggest that the primary response occurs at muscle synapses. We believe that the physiological defect the extremely resistant mutants share is a severe lack of functional muscle acetylcholine receptors and that most of the wild type function of this molecule is not essential to the life of C. elegans. The ability to obtain such mutants may result from there being more than one pharmacological type of nematode cholinergic muscle receptor and/or from the coexistence of a noncholinergic motor mechanism. More generally, the ease with which levamisole-resistant mutants can be isolated (up to 74 mutants in one gene) makes these mutants a favorable system for understanding how a small group of related genes function in a simple animal.     

Sodium dependence of taurine uptake in rat brain synaptosomes

Taurine uptake by synaptosomes isolated from rat brain is strongly inhibited in the absence of sodium ions, in particular within a low concentration range of taurine. Omission of calcium or potassium ions reduces the uptake only slightly. The saturable, high-affinity uptake of taurine is shown to be strictly sodium-dependent, while the low-affinity uptake is only partially sodium-dependent.Sodium ions mimic the actions of allosteric effectors of taurine uptake, showing positive co-operativity. At least three sodium ions may be needed for the transport of one taurine molecule.     

Diazepam stimulates the binding of GABA and muscimol but not THIP to rat brain membranes

Diazepam (10-1000 nM) enhanced the binding of [3H]GABA and of the monocyclic GABA agonist [3H]muscimol, but failed to alter binding of the bicyclic GABA agonist [3H]THIP to fresh, well washed rat brain membranes incubated at 2 degrees C. Although stimulation of [3H]diazepam binding by THIP was observed at higher incubation temperatures and in the presence of chloride ions, these measures did not induce a corresponding enhancement of [3H]THIP binding by diazepam. These results extend earlier observations of the unusual behavior of THIP as a selective GABA agonist, and emphasize that enhancement of benzodiazepine binding by GABA agonists is not necessarily reflected in a complementary manner by any action of benzodiazepines on the binding of GABA agonists.     

The section-Golgi impregnation procedure. 2. Immunocytochemical demonstration of glutamate decarboxylase in Golgi-impregnated neurons and in their afferent synaptic boutons in the visual cortex of the cat

Sections of the cat's visual cortex were stained by an antiserum to glutamate decarboxylase using the peroxidase-antiperoxidase method; they were then impregnated by the section Golgi procedure and finally the Golgi deposit was replaced by gold. Neurons containing glutamate decarboxylase immunoreactivity were found in all layers of the visual cortex, without any obvious pattern of distribution. Fifteen immunoreactive neurons were also Golgi-impregnated and gold-toned, which enabled us to study the morphology and synaptic input of identified GABAergic neurons. These neurons were found to be heterogeneous both with respect to the sizes and shapes of their perikarya and the branching patterns of their dendrites. All the immunoreactive, Golgi-impregnated neurons had smooth dendrites, with only occasional protrusions. The synaptic input of glutamate decarboxylase-immunoreactive neurons was studied in the electron microscope. Immunoreactive neurons received immunoreactive boutons forming symmetrical synapses on their cell bodies. The Golgi-impregnation made it possible to study the input along the dendrites of immunoreactive neurons. One of the large neurons in layer III whose soma was immunoreactive was also Golgi-impregnated: it received numerous non-immunoreactive asymmetrical synaptic contacts along its dendrites and occasional ones on its soma. The same neuron also received a few boutons forming symmetrical synaptic contacts along its Golgi-impregnated dendrites; most of these boutons were immunoreactive for glutamate decarboxylase. Glutamate decarboxylase-immunoreactive boutons were also found in symmetrical synaptic contact with non-immunoreactive neurons that were Golgi-impregnated. A small pyramidal cell in layer III was shown to receive several such boutons along its somatic membrane. It is concluded that the combination of immunoperoxidase staining and Golgi impregnation is technically feasible and that it can provide new information. The present study has shown that there are many morphologically distinct kinds of aspiny GABAergic neurons in the visual cortex; that the predominant type of synaptic input to the dendrites of such neurons is from boutons forming asymmetrical synapses, but that some of the GABAergic neurons also receive a dense symmetrical synaptic input on their cell bodies, and occasional synapses along their dendrites, from the boutons of other GABAergic neurons. These findings provide a morphological basis, firstly, for a presumed powerful excitatory input to GABAergic interneurons and, secondly, for the disinhibition which has been postulated from electrophysiological studies to occur in the cat's visual cortex.     

Biochemical evidence for γ-aminobutyrate containing fibres from the nucleus accumbens to the substantia nigra and ventral tegmental area in the rat

Glutamate decarboxylase activity, a specific marker for γ-aminobutyrate-containing neurons, has been analysed in microdissected samples from rat mesencephalon following unilateral electrocoagulations of the nucleus accumbens. This lesion resulted in a consistent decrease of 50% in the enzyme activity in the rostromedial substantia nigra, and a slight, but insignificant decrease (?15%) in the medial parts of the caudal pars compacta of the substantia nigra. No change was found in the lateral pars compacta or the central pars reticulata. In the ventral tegmental area, the highest activity was found in the rostromedial part, adjacent to the mammillary body. At this level, a significant decrease of 20% was found in the ventral tegmental area on the lesioned side. In contrast, the activities in the medial accessory optic nucleus and the caudal ventral tegmental area adjacent to the interpenduncular nucleus were unchanged.The results indicate that the nucleus accumbens sends γ-aminobutyrate-containing fibres to the rostromedial substantia nigra and to the rostral ventral tegmental area. The caudal ventral tegmental area, the lateral pars compacta and the central pars reticulata do not receive measurable amounts of such fibres.     

Glutamate decarboxylase immunoreactivity in the intermediate grey layer of the superior colliculus in the cat

Recent evidence suggests that gamma-aminobutyrate has a profound influence on the activity of premotor neurons in the intermediate grey layer of the superior colliculus. In the present study an antibody to glutamate decarboxylase, the synthesizing enzyme for gamma-aminobutyrate, was used to identify and characterize the structures in the intermediate grey layer of the cat that use gamma-aminobutyrate as a transmitter. The material was examined with both the light and electron microscope. Glutamate decarboxylase immunoreactivity was confined, for the most part, to axon terminals. Glutamate decarboxylase positive terminals almost completely cover the soma and proximal dendrites of the large neurons that are characteristic of this layer. Other glutamate decarboxylase positive terminals contact smaller, presumably more distal dendrites. By combining the glutamate decarboxylase immunocytochemistry with the retrograde transport of horseradish peroxidase in single animals, it was demonstrated that the cells of origin of the major descending efferent pathway from the intermediate grey layer, the predorsal bundle, are heavily contacted by glutamate decarboxylase immunoreactive terminals.     

Ultrastructural immunocytochemistry of gamma-aminobutyrate in the cerebral and cerebellar cortex of the rat

gamma-Aminobutyrate containing structures in the cerebral and cerebellar cortex of the rat were visualized by an immunocytochemical method using glutaraldehyde fixation and an antiserum developed against a gamma-aminobutyrate-glutaraldehyde-protein conjugate. Labelled elements (perikarya and cell processes) were observed to be distributed throughout the layers of the cerebral cortex in a pattern similar to that described using glutamate decarboxylase immunocytochemistry. The morphological features of many immunoreactive cell bodies were typical of stellate neurons. In the cerebellar cortex, Purkinje, basket, Golgi and stellate, cell bodies were found to be immunoreactive along with numerous labelled neuronal processes. At the ultrastructural level, the labelled processes in both areas corresponded to immunoreactive dendrites and fibres. Labelled synaptic boutons, generally of the symmetrical type, could also be seen in contact with positive or negative cell bodies and dendrites. In the cerebellum, glomeruli could be clearly identified including mossy fibres surrounded by unlabelled dendrites in contact with immunoreactive terminals. At the subcellular level in both brain regions, the areas occupied by the Golgi apparatus were never labelled, although the nuclei had varied reactions. The strong glutaraldehyde fixation that limits the diffusion of gamma-aminobutyrate limits also antibody diffusion. However, this fixation is compatible with a good morphological preservation and should enable immunocytochemistry studies to be compared to other methods such as autoradiography.     

Brain gamma-aminobutyric acid and benzodiazepine receptor binding in dialysis encephalopathy

We measured gamma-aminobutyric acid (GABA) and benzodiazepine binding in autopsied frontal cortex of 8 patients dying with dialysis encephalopathy (DE). No alteration in [3H] GABA binding was observed. However, a mild reduction (-23%, P less than 0.05) of [3H] flunitrazepam-binding density was found in DE cortex. The magnitude of this reduction was similar to that observed in frontal cortex of amygdala-kindled rats [10]. We suggest that a reduction in benzodiazepine receptor number, in combination with markedly reduced GABA concentration in DE cerebral cortex may contribute to some of the clinical features (especially seizures) characteristically observed in this syndrome.