Barbiturate depresses simple spike activity of cerebellar Purkinje cells after climbing fiber input.

1. Some scientists reported that the simple spike (SS) activity was transiently depressed after climbing fiber input, but others reported that predominant population of Purkinje cells increased their SS activity after the complex spike (CS). In the present study, SS activity after spontaneous CS was compared before and after the administration of pentobarbital sodium and of ketamine in high decerebrate cats. 2. Frequencies of spontaneous CS and SS firing were reduced (P < 0.001, t test) after pentobarbital administration of a total dose of 20-30 mg/kg. 3. In the peri-CS time histogram, the SS activity during a post-CS period of 10-110 ms with respect to that during a pre-CS period of -100-0 ms was reduced (P < 0.001) after the pentobarbital administration from, on average, 132.4 to 81.9%. In contrast, the SS activity during a post-CS period of 110-210 ms remained unchanged (P > 0.2). 4. In the pre-CS time histogram constructed after the pentobarbital administration, there were no significant differences (P > 0.01) between the SS activity during a pre-CS period of -600 to -500 ms and that during each of other pre-CS periods, suggesting that the barbiturate had little effect on the SS activity preceding the CS. 5. Analysis of raster diagrams revealed the variability of individual SS activity after the CS.(ABSTRACT TRUNCATED AT 250 WORDS)