Convulsant versus typical barbiturates: effects on conflict behavior in the rat.

Typical barbiturates produce a spectrum of behavioral effects, including anti-convulsant, muscle relaxant, sedative hypnotic and anti-anxiety actions. In contrast to these typical barbiturates, there exists a group of barbiturates which are pro-, rather than anti-convulsant. The effects of these convulsant barbiturates on anxiety-related behaviors have not been examined. Therefore, the present studies were designed to compare the effects of the convulsant barbiturate CHEB to those of a number of typical barbiturates in the Conditioned Suppression of Drinking (CSD) paradigm, an "animal model" for the study of anxiety and anti-anxiety agents. In daily 10-minute sessions, water-deprived rats were trained to drink from a tube which was occasionally electrified (0.5 mA), electrification being signalled by a tone. Within 3-4 weeks control responding had stabilized (10-15 shocks and 10-15 ml water/session); drug tests were then conducted at weekly intervals. Consistent with previous reports, typical barbiturates (pentobarbital, secobarbital, phenobarbital) produced dose-dependent increases in the number of shocks received at doses which did not depress background responding (water intake). In contrast, sub-convulsant doses of CHEB (0.3-2.5 mg/kg) produced a dose-dependent depression of both punished responding and background responding. Finally, it was found that pre-treatment with 1.25 mg/kg CHEB did not alter the anti-conflict effects of pentobarbital. These results suggest that (1) convulsant and typical barbiturates have markedly different effects on conflict behavior in the rat and (2) CHEB appears not to possess any "barbiturate antagonist" qualities.