EFFECTS OF N‐METHYLAMINO ACIDS AND CONVULSANTS ON SPONTANEOUS ACTION POTENTIALS IN GUINEA‐PIG CEREBELLAR SLICES

• Published in: British journal of pharmacology 1977-04, Vol.59 (4), p.551-560
• Main Authors: OKAMOTO, K., QUASTEL, J.H.
• Format: Article
• Language: English
• Subjects: Action Potentials - drug effects; Amino Acids - pharmacology; Animals; Cerebellum - drug effects; Cerebellum - physiology; Convulsants - pharmacology; Drug Interactions; Glutamates - pharmacology; Guinea Pigs; In Vitro Techniques; Kinetics; Methylation; Picrotoxin - pharmacology; Strychnine - pharmacology
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.1977.tb07720.x

1 N‐methyl‐γ‐aminobutyrate (N‐methylGABA), N‐methylglycine, N‐methyltaurine and N‐methylβ‐alanine diminished the frequency of spontaneous spike discharges in guinea‐pig cerebellar slices. Usually a weak excitatory effect preceded the inhibition. 2 The inhibitory effects of N‐methylGABA and N‐methylβ‐alanine were competitively antagonized by both picrotoxin and strychnine. 3 The inhibitory action of N‐methyltaurine was competitively suppressed by strychnine and by low concentrations of picrotoxin. 4 The inhibitory action of N‐methylglycine was suppressed by strychnine but not by picrotoxin. The suppression was competitive at low concentrations of strychnine. 5 N‐methyldl‐glutamate brought about a strong inhibition followed by a strong excitation of the neurones. The inhibitory effects were competitively suppressed by both picrotoxin and strychnine. Neither convulsant affected the excitation. 6 Whereas l‐ or D‐glutamate caused only excitation in the majority of cells examined, a small proportion of the cells exhibited inhibition preceding the excitation by l‐ or D‐glutamate. Such inhibitory effects were suppressed by picrotoxin but not by strychnine. 7 Kinetic analyses of the dose‐response curves for the N‐methylamino acid in the presence or absence of the convulsant indicated that the number of molecules of the amino acid combining with the receptor site to produce a response was 3 for N‐methylGABA, 2 for N‐methylglycine, 3 for N‐methyltaurine, 3 for N‐methylβ‐alanine. The corresponding value was 1 for N‐methyldl‐glutamate (inhibition). The number of molecules of convulsant combining with the receptor site was calculated to be 2 for picrotoxin with N‐methylGABA, N‐methylβ‐alanine and N‐methyldl‐glutamate and 1 for strychnine with all N‐methylamino acids examined.