p-Chlorophenylalanine effects on shock-induced attack and pressing responses in rats

The literature concerning the effects of d,1-parachlorophenylalanine (PCPA) upon shock-induced aggression (SIA) was examined and found to be inconsistent. PCPA, a known serotonin depletor, has behavioral effects in a variety of other procedures which collectively suggest that PCPA should produce SIA enhancement. The present study analyzed PCPA (300 mg/kg, IP) effects upon SIA in rats restrained spatially close to an inanimate target and panel operandum. The results showed marked increases in both aggressive biting and panel-pressing for several days following each PCPA treatment, for each subject tested. These data were interpreted to indicate that serotonin depletion by PCPA does indeed enhance SIA but that this effect is not selective for aggression. Potential controlling variables are suggested to account for reports of no effect on SIA after PCPA treatment. It is concluded that procedural variables may be the critical determinants of variation in reported PCPA-aggression effects across studies, rather that hypothesized differences in neurochemical mediators.