Alteration in the sexual behaviour of male and female rats after neonatal administration of p-chlorophenylalanine

Abstract

p-Chlorophenylalanine (pCPA) was administered to male and female rats on the 2nd and 3rd (20 mg/kg) and on the 5th and 6th (100 mg/kg) postnatal day. The display of spontaneous and hormone induced adult sexual behaviour, the onset of puberty in the females, and the effect of the neonatal drug injections on serotonin and 5-hydroxyindole acetic acid levels in the brains of 15-day-old rats were examined. In the females, the time of vaginal opening was delayed even though the vaginal cytological cycles appeared to be normal. In addition, these females showed less ear wiggling activity during both spontaneous and hormone induced copulatory behaviour and a tendency to shortening of mount latencies during hormone induced masculine sexual behaviour. The drug treated males were, as adults, generally more sexually facile than were the vehicle treated controls: they required fewer mounts and intromissions prior to ejaculation, and displayed shorter intromission and ejaculation latencies as well as shorter refractory periods and intervals between successive intromissions. The hormone induced female sexual behaviour in the drug treated males appeared, however, to be unaltered. Finally, although many differences in adult sexual behaviour were observed in the animals treated with pCPA shortly after birth, no changes or sex differences in hypothalamic or forebrain concentrations of serotonin or 5-hydroxyindole acetic acid were found in animals treated similarly in infancy but killed at the age of 15 days. The relevance of these findings is discussed in the light of the possible significance of brain indole amines during the sexual development and differentiation.