DIFFERENTIAL INVOLVEMENT OF VOLTAGE-DEPENDENT CALCIUM CHANNELS IN APOMORPHINE-INDUCED HYPERMOTILITY AND STEREOTYPY

The involvement of the voltage-dependent calcium channel in behavioral effects of apomorphine was tested in naive rats and in animals which were morphine-abstinent or were subjected to chronic electroconvulsive treatment (ECS). In naive rats a calcium channel blocker, nifedipine, which by itself does not affect locomotor activity, inhibited the loc omotor stimulation induced by apomorphine, while it facilitated stereo typed behavior. Morphine-abstinent and ECS-treated rats displayed elev ated responsiveness to apomorphine, reflected by hypermotility and ste reotyped behavior after a dose of 1 mg/kg IP that does not produce ove rt behavioral effects in naive animals. Nifedipine, 5 mg/kg IP, signif icantly reduced hypermotility produced by apomorphine in morphine abst inent or ECS-treated rats. The calcium channel blocker did not, howeve r, antagonize enhanced stereotyped behavior. The results indicate that apomorphine hypermotility is controlled by dihydropyridine calcium ch annels and that enhancement of calcium channel density produced by mor phine abstinence and by chronic ECS potentiates the hypermotility resp onse. Calcium channels seem to be differently involved in control of a pomorphine-induced hypermotility and stereotypy.