Search PubMed⌕ Search

Biomedical subjects

M Segal

Publications and source records attributed to M Segal.

At least 343 records · Page 19Linked to original sources
PubMed1975

Physiological and pharmacological evidence for a serotonergic projection to the hippocampus.

Rat hippocampal pyramidal cells were studied for their response to serotonin applied iontophoretically and to stimulation of the midbrain raphe nuclei. Ninety-two percent of the cells studied were inhibited by serotonin. Fourty-eight percent of the cells responded by inhibition to dorsal and median raphe stimulation. The inhibitory response to raphe stimulation was absent when the rats were pretreated with p-chlorophenylalanine (PCPA), a serotonin synthesis inhibitor; PCPA effects were alleviated by 5-HTP or 5-HT administration. The response to raphe stimulation was blocked by emthysergide and cyproheptadine. The responses to raphe stimulation were potentiated by chlorimipramine, a serotonin reuptake blocker. These data satisfy several of the criteria required to identify serotonin as the inhibitory neurotransmitter for the raphe-hippocampal pathway

5-Hydroxytryptophan↗
PubMed1975

Hippocampal conditioned responses in the absence of entorhinal input.

Hippocampal unit responses to conditioned stimuli were analyzed in intact rats and in rats deprived of the input from the entorhinal cortex to the hippocampus. Cells in normal rats responded more intensely to a conditioned stimulus when it was applied within 1 min from a previous one. The rats with lesions had smaller conditioned hippocampal responses and, in addition, there were no differences between responses to stimuli applied after short or long intertrial intervals. No effects on gross conditioned behavior were noticed.

Acoustic Stimulation↗
PubMed1975

Characterization of an inhibitory receptor in rat hippocampus: a microiontophoretic study using conformationally restricted amino acid analogues.

1 Pyramidal cells in rat hippocampus were used to study the molecular dimensions of a receptor for inhibitory amino acids in the central nervous system. The inhibitory potencies of gamma-aminobutyrate (GABA), beta-alanine and glycine were compared by standard microiontophoretic techniques. Subsequently, rigid cyclopentane and cyclohexane amino acid analogues were applied by iontophoresis and their relative efficacies were compared with those of the naturally occurring amino acids.2 GABA was the most effective of the small aliphatic amino acids in producing inhibition of the firing of hippocampal pyramidal neurones. beta-Alanine was less effective and glycine was the least effective. GABA-induced inhibition was antagonized by concurrent iontophoresis of picrotoxin or bicuculline, whereas strychnine did not antagonize GABA inhibition.3 The ability of the series of substituted aminocyclopentane and aminocyclohexane carboxylic acids to produce inhibition of pyramidal cells was a direct function of the separation of amino and carboxylic acid groups. In both series of the cyclic amino acids the most potent inhibition was demonstrated when the spatial separation was similar to that of the extended GABA molecule (4.74 A). Additionally, the inhibition of hippocampal pyramidal cells by (+/--cis-3-amino-cyclopentanecarboxylic acid, like that produced by GABA, could be blocked by simultaneous application of picrotoxin or bicuculline, but not by strychnine.4 The present results suggest that the physiologically active conformation of GABA is the fully extended molecule, and additionally indicate that one dimension of the postsynaptic receptor site is within the range of 4.2 to 4.8 ångströms.

Amino Acids↗