A frequency analysis of behavior components of the serotonin syndrome produced by p-chloroamphetamine.

A time-sampling frequency analysis was made of criterion behaviors following injection of 2.5--10 mg/kg dosages of p-chloroamphetamine (PCA). Stereotypic behaviors (forepaw treading, circling, head weaving and inching) increased with increasing dosages and normal behaviors (grooming, rearing, and instances of inactivity) decreased. Composite scores of stereotypic behavior were a positive, linear function of PCA dosage. Composite scores of normal behavior showed near maximal inhibition at 5 mg/kg. Splayed hindlimbs is a reliable and sensitive indicator of PCA action, but vocalization, tremors, diarrhea and autonomic signs are not. Preinjection of PCA strongly attenuated the PCA-induec syndrome, as expected, since the preinjection should deplete brain serotonin and reduce the amount released by the second PCA injection.