Abolition of monocular optokinetic nystagmus directional asymmetry after unilateral visual deprivation in adult vertebrates: involvement of the GABAergic mechanism.

In lower vertebrates such as frogs and chickens, monocular optokinetic nystagmus (OKN) displays directional asymmetry, temporal-nasal (T-N) stimulation being more efficient in evoking this visuomotor reflex than N-T stimulation. The N-T component of monocular OKN is significantly weaker in chickens, while it is almost absent in frogs. Coil recordings showed that in adult frogs and chickens, prolonged monocular visual deprivation by unilateral eyelid suture provoked the appearance of the N-T component in frogs as well as its significant and progressive increase in both species.

Behavioral analysis of the effects of benzodiazepine receptor ligands in the conditioned burying paradigm.

In the conditioned burying paradigm, 10 mutually exclusive behavioral sequences were encoded in order to characterize the effects of various benzodiazepine receptor ligands. It was found that each ligand produced a specific behavioral pattern, the elements of which were consistent with results obtained in other experimental situations. Whereas anxiolytic (diazepam, Ro 16-6028) and 'anxiogenic' ligands (FG 7142) both decreased the mean duration of burying, these two classes of drugs largely differed when approaches to the prod and escape movements away from the prod were considered.

Aversion induced by electrical stimulation of the mesencephalic locomotor region in the intact and freely moving rat.

Electrical stimulation of the so-called "mesencephalic locomotor region" (MLR) in the acute mesencephalic and restrained rat is known to induce locomotion. In the intact and freely moving rat, electrical stimulation of an area coextensive with MLR is reported to elicit an apparently aversive type of behavioral response. Indeed, the description of this behavioral response is very similar to the description of the prototypical escape reaction elicited by electrical stimulation of the periaqueductal gray (PAG), a structure of the so-called "brain aversive system.

Time-dependent effects of intrahippocampal grafts in rats with fimbria-fornix lesions.

Based on three experiments, this study examined whether behavioral and histological effects of fetal septal or hippocampal grafts placed in the denervated hippocampus depend on the duration of post-grafting delays. Each experiment included four groups of rats: sham-operated rats (Sham), rats with aspirative lesions of the fimbria-fornix (Fifo) and rats given both Fifo lesions and intrahippocampal fetal suspension grafts of either septal (Fifo.ST) or hippocampal (Fifo.

[Presence of antibodies to lectin CSL in the blood of patients with multiple sclerosis patients].

We have recently shown (Zanetta et al., Lancet, 335, 1990, pp. 1482-1484) that antibodies to the protein CSL (an endogenous lectin involved in myelination) are present in the cerebrospinal fluid of patients with multiple sclerosis.

Alteration of benzodiazepine receptors in mouse cerebellum following methylazoxymethanol treatment during development.

The specific binding of [3H]flunitrazepam was studied to biochemically specify the morphological alterations induced in mouse cerebellum by a single injection of an antimitotic agent, methylazoxymethanol (MAM) performed at the beginning of the postnatal life. The MAM injection causes a general reduction of the benzodiazepine receptors in the adult mice which is particularly severe in mice having been injected the 1st day of postnatal life (so-called MAM0 mice) as compared to animals injected the 5th day (MAM5 mice): in MAM0 mice the benzodiazepine receptor is reduced to half of the control value. The affinity of the benzodiazepine towards its receptor was not affected and the topographic and biochemical action of MAM in the central nervous system was ascertained.

Effect of a single dose of beta,beta'-iminodipropionitrile in vivo on the properties of neurofilaments in vitro: comparison with the effect of iminodipropionitrile added directly to neurofilaments in vitro.

The biochemical properties of neurofilaments isolated from control and iminodipropionitrile-treated rats were compared with regard to autophosphorylation capacity, hydrolysis of ATP, and the formation of a viscous gel between filaments. Both preparations exhibited a similar polypeptide composition, and no covalent cross-linking between neurofilament subunits was induced by iminodipropionitrile in vivo. An ATPase activity, systematically present in all preparations, was unaffected by the administration of iminodipropionitrile to the rats.

Neurotransmission in the frog retina: possible physiological and histological correlations.

In the frog retina, extracellular recordings of transient ganglion cells have shown that the inhibitory surround of the receptive field of these cells was mediated by gamma-aminobutyric acid and acetylcholine (through the nicotinic receptors). Histoautoradiographic and immunocytochemical studies for the two respectively have shown that these neurotransmitters can act through horizontal and amacrine cells. The separation of the ON and OFF channels mediated by glutamate at the bipolar cell level may also be obtained by glycine and/or acetylcholine (through muscarinic receptors).

Effects of unilateral microinjections of GABAergic drugs into the inferior colliculus on auditory evoked potentials and on audiogenic seizure susceptibility.

Alteration of GABAergic neurotransmission within the inferior colliculus (IC) appears to be involved in the generation of the audiogenic seizure (AGS) susceptibility. In the present study, we provide evidence indicating that this susceptibility may result from IC neuronal hyperexcitability to sound induced by a decreased GABAergic inhibition. In a first experiment, a unilateral microinjection of bicuculline, a GABAa antagonist, into the IC of normal rats increased the amplitude of the collicular auditory evoked potential, while the microinjection of THIP, a GABAa agonist, decreased this response.

Conditioned place aversion produced by microinjections of semicarbazide into the periaqueductal gray of the rat.

Previous studies have shown that the blockade of GABA-ergic neurotransmission in the periaqueductal gray (PAG) of the rat induce flight reactions. The present study examined whether a negative affective state was produced by such a blockade. Microinjections of semicarbazide, a GABA synthesis inhibitor, into the PAG were found to produce a conditioned place aversion.

Choline acetyltransferase-like activity bound to neuronal plasma membranes.

A form of CAT-like activity was found bound present in rat brain synaptosomal membranes which could be recovered in the Triton X-114 phase. The enzyme activity was slightly activated by NaCl, had a pH maximum around 8 and showed a temperature dependence with a Q10 of 2.28.

Expression of neurofilament proteins by Purkinje cells: ultrastructural immunolocalization with monoclonal antibodies.

Purkinje cell bodies in rodent cerebellum have been shown to express neurofilament protein epitopes but neurofilaments are rarely seen in these perikarya by classical morphological approaches. In an attempt to solve this enigma the ultrastructural distribution of two neurofilament epitopes was studied by immunoelectron microscopy with two monoclonal antibodies (Mabs) of divergent specificity: one, Mab 04-7 recognized a phosphorylated epitope, the other, Mab 02-135 a non-phosphorylated epitope. Longitudinal filamentous elements were heavily labeled in basket cell axons and afferent nerve fibers with both Mabs.

Influence of the phosphorylation state of neurofilament proteins on the interactions between purified filaments in vitro.

The extensive enzymic dephosphorylation of neurofilaments determined the progressive loss of their capacity to interconnect in vitro into a reticulated network, measured by the formation of highly viscous gels in purified preparations of neurofilaments [Leterrier & Eyer (1987) Biochem. J. 245, 93-101].

Studies on the 240-kDa Con A-binding glycoprotein of rat cerebellum, a putative marker of synaptic junctions.

A Con A-binding glycoprotein of Mr 240,000 was isolated from the remaining residue of rat cerebella after sequential extraction with buffers supplemented with or without neutral detergents. It was further purified by affinity chromatography on Con A-Sepharose in the presence of sodium dodecyl sulfate and preparative gel electrophoresis. This glycoprotein partially resists Triton X-100 extraction and is soluble in N-lauryl sarcosinate.

Evidence that activation of GABA receptors in the substantia nigra suppresses spontaneous spike-and-wave discharges in the rat.

The involvement of intranigral gamma-aminobutyric acid (GABA) receptors in the control of generalized non-convulsive epilepsy was investigated in a genetically determined model of petit mal epilepsy in the rat. Bilateral intranigral injection of muscimol (2 ng/0.2 microliter/side), a GABA agonist, significantly suppressed EEG-recorded spike-and-wave discharges for about 80 min, both at the cortical and thalamic levels.

Regional differences in depolarization-induced release of gamma-hydroxybutyrate from rat brain slices.

gamma-Hydroxybutyrate (GHB), an endogenous compound in mammalian brain which possesses important neuroregulatory properties, has been proposed as a neurotransmitter. The present report concerns the heterogeneous regional characteristics of depolarization-induced gamma-[3H]hydroxybutyrate ([3H]GHB) release in rat brain slices. The Ca2+-dependent component of [3H]GHB release in cerebellum and pons-medulla, areas with low concentrations of GHB binding sites, is only about 23% of that in hippocampus, striatum and frontoparietal cortex, all areas rich in binding sites.

GAD immunoreactivity in pretectal and accessory optic nuclei of the frog mesencephalon.

By an immunocytochemical technique using anti-GAD antibodies, we found a high density of GAD-immunoreactive puncta in the 5 pretectal nuclei and in the nucleus of the basal optic root. These results back up the suggestion that GABAergic modulation of the output of the visual pretectal relay nuclei might underlie the directional asymmetry of the horizontal optokinetic nystagmus and the directional selectivity of pretectal neurons.

[Proliferation of oligodendrocytes is stimulated after their adhesion on a matrix made up of a nerve lectin, CSL].

It is shown that oligodendrocytes (myelin producing cells in the central nervous system) can adhere to a substratum constituted by an endogenous cerebellar soluble lectin (CSL) adsorbed on plastic Petri dishes. This adhesion induces a rapid and important proliferation of cultured oligodendrocytes.

On cholinergic mechanisms in the optokinetic nystagmus of the frog: antagonistic effects of muscarinic and nicotinic systems.

In a monocular situation, an intravitreal injection of acetylcholine (ACh) agonists (especially muscarinic agonists like muscarine or oxotremorine) provoked both the suppression of the optokinetic nystagmus (OKN) related to the injected eye, and the appearance of a nasal-temporal (N-T) component in the OKN triggered by the contralateral non-injected eye. These two effects were added in a binocular condition. Similar results were obtained with ACh nicotinic antagonists (D-tubocurarine, alpha-bungarotoxin, hexamethonium and gallamine).

Ultrastructural localization of fibroblast growth factor in neurons of rat brain.

The distribution of fibroblast growth factor (FGF) at the ultrastructural level in the brain of young (15- and 20-day-old) and adult (3-month-old) rats was investigated by immunocytochemistry. Strong staining was observed in most neurons of the cortex of young rat brain. In the same brain area of adult rat many neurons were also stained intensely, while others were negative.

Spike trains in rat periaqueductal gray depend on the stochastic properties of interacting electrical stimulation trains.

Spike trains flowing into the periaqueductal gray (PAG) might be discriminated from one another by PAG neurons on the basis of the distribution or sequence of their respective interspike intervals. The various sequences of interspike intervals characteristic of spontaneous PAG unit activities were assessed in a preliminary experiment. These sequences were then simulated by means of appropriate mathematical functions.

Effect of iron and transferrin on pure oligodendrocytes in culture; characterization of a high-affinity transferrin receptor at different ages.

Oligodendrocytes in pure culture can grow on relatively low iron concentrations (0.1-0.3 microM), in the absence of transferrin; with micromolar concentrations of iron, toxic effects can be seen after one week in culture.

Properties of highly viscous gels formed by neurofilaments in vitro. A possible consequence of a specific inter-filament cross-bridging.

Neurofilaments freshly isolated from bovine spinal cord form a reversible gel in vitro, consisting of nearly parallel and interlinked filaments organized in bundles. This phenomenon is obtained above a critical neurofilament concentration and is highly sensitive to denaturation. No gelation occurs with neurofilaments reconstituted from urea-solubilized subunits.

[Contribution of internal layers of the retina to the genesis of the light peak in the electrooculogram in the chicken].

We report that in the Chicken retina, Na aspartate which selectively blocks signal transmission between the photoreceptors and second order neurons also largely modifies the EOG. In treated eyes, the standing potential is reduced and the LP which is very transient in the Chicken eye is substituted for by a reactivity to light with much slower rise and delayed culmination time. The data are discussed in terms of interaction between pigment epithelium and neuroretina in the pharmacological determinism of the LP.

[Immunocytochemical localization of endogenous lectin during the development of the cerebellum in the rat].

An endogenous cerebellar lectin (called CSL) was localized immunocytochemically using antibodies against the antigen. It was found that the lectin is not specifically localized in one of the nervous cell types. This compound, intracellularly localized in adult tissue, accumulated in the cerebellar premigratory zone and in white matter of young rats, suggesting the involvement of this molecule in contact guidance of cell migration and in myelination.