Facilitatory effect of phenobarbital on shock-elicited jumping behavior in rats.

Recently we found that the marked behavioral difference between isolated and grouped rats occurred under foot shock situations by measuring frequency of jumping behavior in rats (Nishikawa and Tanaka, 1978). We also postulated by the results of methamphetamine administration and the behavioral findings that catecholaminergic hyperactivity especially receptor supersensitivity might play a role in the isolation-induced behavioral changes under foot shock situations. Further study revealed that jumping behavior might be mediated mainly by central noradrenergic neurons, since jumping frequency was facilitated markedly by methamphetamine and slightly by L DOPA but not by the dopaminergic receptor stimulant, apomorphine (Funatsu, 1978). Such catecholaminergic antagonistic agents as a -methyl-ptyrosine, f usaric acid, disulf i ram, chlorpromazine and reserpine decreased jumping frequency. Agonistic and antagonistic agents of serotonin, 5hydroxy-tryptophan and p-chlor-phenylalanine, did not show any effect on jumping frequency (Funatsu, 1978). In the present study, we report the further pharmacological characteristics of jumping behavior, wherein jumping frequency is facilitated by one of the depressants of central nervous system, phenobarbital. Fifty-six male Wistar rats weighing 200g 250g were subjected to the study. All animals were kept at constant room temperature (24 •} 1 •Ž) and humidity (50 •} 10 %). Lights were on from 7 : 00 a. m. to 7 : 00 p. m. and food and water were given ad libitum. The apparatus for electric foot shock was a plexi-