Effect of serotonergic agents on neuroleptic induced catalepsy in rats.

Three pharmacological tools namely zimelidine, danitracen and MK 212, were selected to examine the nature of involvement of serotonergic neurotransmission in catalepsy, an undesirable side effect following administration of neuroleptics in rats. Reserpine and haloperidol were chosen as cataleptogenic challenges. Zimelidine, a serotonin (5-HT) reuptake blocker, inhibited the manifestation of reserpine and haloperidol induced catalepsy. However, a dose dependent effect could not be demonstrated beyond 30 mumoles/kg. Danitracen, a 5-HT receptor blocker, prevented the occurrence of the symptoms that were observed following reserpine treatment but it could not elicit blockade of haloperidol response. MK 212, an S2 (5-HT2) receptor stimulant forestalled the occurrence of reserpine syndrome at lower doses but exhibited cataleptogenic effects at higher doses. Besides, MK 212 failed to influence catalepsy following administration of haloperidol. It appears that 5-HT exerts a homoeostatic control in the regulatory neuraxis in neuroleptic induced neurological side effects.