Abstract
Effects of diazepam and baclofen on the anemic decerebrate rigidity in rats were studied by using the drugs that modify GABAergic mechanisms or deplete catecholamine. Rigid forelimb tension in anemic decerebrate rats took the form of tonically sustained tension (tonic component), while the phasic tension (phasic component) was induced by mechanical stimulation of hindlimbs. Diazepam exerted a marked dose-dependent inhibition of the phasic component, whereas baclofen produced a similar effect on both tonic and phasic components. In rats pretreated with semicarbazide, the inhibitory effect of diazepam on phasic component was reduced, and the effect of semicarbazide was antagonized by pyridoxine. The effect of diazepam was slightly enhanced by pretreatment with aminooxyacetic acid, and antagonized by picrotoxin. In contrast to diazepam, the depressant actions of baclofen on both components were not affected by semicarbazide, aminooxyacetic acid or picrotoxin. Catecholamine depletion produced by a-methyltyrosine or disulfiram significantly reduced the effect of baclofen on the phasic component. It thus appears that GABA is involved in the effect of diazepam on the phasic component, and noradrenaline is involved in the same effect of baclofen in anemic decerebrate rats.
