Influence of 6-hydroxydopamine on the behavioral effects induced by apomorphine or clonidine in rats

Abstract

The aim of this paper is to examine if central chemical sympathectomy induced by two injections of 6-hydroxydopamine (6-OHDA) in a dose of 250 μg intracerebroventricularly (k.c.v.) affects behavioral phenomena elicited by apomorphine (AP) (1 or 1.2 mg/kg i.p.) or clonidine (CL) (0.1 mg/kg, 5 or 1 μg/kg i.p.). Experiments were carried out on male Wistar rats. The time of duration of several components of behavior and the degree of irritability of rats were measured. Moreover, open field and hole test were performed. The lower dose of AP did not affected behavior of rats. The higher dose increased the locomotor and exploratory activity of animals. 6-OHDA potentiated these effects of AP. CL (0.1 mg/kg) had a depressive effect on the rats' behavior, which was potentiated by 6-OHDA. CL (5 μg/kg) had no effect on the rats' behavior, but in a dose of 1 μg/kg caused excitatory behavior. This type of behavior was abolished by 6-OHDA. In conclusion, central chemical sympathectomy caused increased sensitivity of the central nervous system on AP. Excitatory behavioral effects of CL in low dosage may be connected with stimulation of central adrenergic receptors. Depressive behavioral effect of CL in high dosage is unspecific. Central chemical sympathectomy affects by different methods the reactivity of dopaminergic and noradrenergic neurons.