The effect of L-3,4-dihydroxyphenylalanine (L-dopa) on the prolactin response to sexual behavior in the male rat.

L-3,4-dihydroxyphenylalanine (L-dopa) was administered intraperitoneally (i.p.) to sexually experienced male rats, and blood was collected both by decapitation without anesthesia and by cardiac puncture with ether anesthesia. Samples were taken before and during mating with a receptive female. Both the prolactin (Prl) response to ether and the Prl response to mating were suppressed by L-dopa. Basal Prl levels were depressed, but not significantly. However, sexual behavior was not altered by L-dopa. It was concluded that the previously reported loss of the Prl response to an estrous female in male rats lesioned in the medial preoptic area (MPOA) could not account for their loss of sexual behavior. Further, elevation of Prl levels during mating is not necessary to normal sexual behavior in the intact male rat.