SIMILARITY OF CLOZAPINES AND OLANZAPINES ACUTE EFFECTS ON RATS LAPPING BEHAVIOR

As a way of further comparing the behavioral effects of clozapine and olanzapine, dose ranges of these drugs were studied in a task emphasiz ing fine motor detail of rats' tongue movements during lapping behavio r. Rats lapped drops of tap water from a force-sensing disk. From this behavior four variables were derived: peak-force of tongue strikes, d uration of tongue contact, number of separate tongue contacts in 2 min , and the rhythm of the lapping behavior as quantified by Fourier anal ysis. Both clozapine (0.5-4.0 mg/kg, IP, 45 min) and olanzapine (0.25- 2.0 mg/kg, IP, 45 min) dose dependently reduced all four measures of b ehavior. With respect to lick rhythm, a behavioral marker which clearl y distinguishes haloperidol from clozapine in this behavioral paradigm , olanzapine was about twice as potent as clozapine, with the two drug s having parallel dose-effect functions. Within-session decrements in behavior previously reported for haloperidol in the lick task were not produced by clozapine nor by olanzapine. Taken together, these data s trengthen the idea that the behavioral effects of clozapine and olanza pine are strikingly similar, and thereby emphasize the potential of ol anzapine as an atypical antipsychotic agent.