The striatal dopaminergic catalepsy mechanism is not necessary for the expression of pontine catalepsy produced by carbachol injections into the pontine reticular formation.

Abstract

We have found previously that microinjections of carbachol into the pontine reticular formation (PRF) of rats induce an intense cataleptic state which is similar behaviorally with the catalepsy induced by systemic administration of neuroleptic drugs. In the experiments described in the present article we studied the possibility that the pontine carbachol catalepsy is generated via the intermediary of the dopaminergic cataleptogenic mechanism in the striatum. To this purpose we produced kainic acid lesions in the striatum and in the output stations of the striatal cataleptogenic mechanism-substantia nigra reticulata and the VM thalamic nucleus. Catalepsy was tested after systemic haloperidol (2 mg/kg) and pontine microinjections of carbachol (5 micrograms/1 microliter) before and after the kainic lesions. The cataleptogenic effect of carbachol injected in the pons was not attenuated by any of the three types of lesions. On the contrary, the cataleptogenic effect of haloperidol was greatly attenuated by the same lesions. These results suggest that the pontine catalepsy produced by microinjections of carbachol in PRF is generated independently of the dopaminergic cataleptogenic mechanism in basal ganglia.