p-Chloroamphetamine: effects on tonic immobility, activity, and temperature in chickens.

The effects of p-chloramphetamine (PCA) on tonic immobility (TI) duration, activity, and temperature in chickens were examined in six experiments. In Experiment 1, intraperitoneal doses of 10 or 15 mg/kg PCA produced a significant attenuation of TI duration. The involvement of norepinephrine or dopamine in this effect is questionable since catecholamine synthesis inhibition with alpha-methyl-p-tyrosine in Experiment 2 did not alter the PCA attenuation of TI duration. However, in the third and fourth experiments, serotonin synthesis inhibition with p-chlorophenylalanine produced a blockade of the PCA effect on TI when subjects were tested at 60, but not 10, min after PCA injection. A competing response interpretation of the PCA effect in terms of enhanced motor activity was ruled out in Experiment 5 since, in contrast to the hyperactivity observed in mammals, PCA produced a decrease in both open-field and stabilimeter activity. A PCA-induced decrease in core temperature was observed in Experiment 6, and this effect also contrasts with the hyperthermia reported in rats following PCA injection. These results provide additional evidence that drug treatments that produce a serotonergic behavioral syndrome in rats result in attenuated TI duration in chickens, and they further document the existence of a curious mammalian-avian reversal in drug effects.