Prolactin induces grooming in the rat: possible involvement of nigrostriatal dopaminergic system

The possibility that Prolactin-induced grooming involves the nigrostriatal dopaminergic system was studied. Intracerebroventricular injection of rat Prolactin (PRL) in an amount of 10 micrograms induced grooming in male rats, and neostriatal injection of haloperidol (1 microgram/1 microliter) markedly suppressed this effect. Local administration of 6-OHDA in the substantia nigra also abolished the influence of intracerebroventricularly administered PRL. Bilateral injections of PRL (10 micrograms/l microliters) in the neostriatum failed to induce grooming, whereas bilateral injections of peptide into the substantia nigra (1 microgram/0.5 micrograms) elicited the behavioral response. It is probable that PRL induces grooming in the rat by interacting with the nigrostriatal dopaminergic transmission through an action on the cell bodies rather than in presynaptic terminals or at the postsynaptic level of this system.