Neuropeptides related to neurohypophyseal hormones interfere with apomorphine-induced behavioral changes

Abstract

The interaction between peptides related to neurohypophyseal hormones and brain dopaminergic systems was studied by investigating in rats the effect of these peptides on behavioral changes induced by graded doses of the specific dopamine agonist apomorphine. Low doses of this drug induce hypoactivity of the animals, while higher doses result in hyperactivity and stereotyped sniffing. Desglycinamideg[Arg8]vasopressin (DG-AVP), prolyl-leucyl-glycinamide (PLG) and oxytocin did not interfere with the behavioral responses induced by the higher doses of apomorphine. Peptide treatment made the rats more sensitive to apomorphine with respect to the drug induced hypoactivity. PLG and especially DG-AVP were more effective than oxytocin. It is concluded that these peptides may have a selective action on distinct dopaminergic receptor systems in the brain, that are presumably located presynaptically in the nucleus accumbens area.

Oxytocin modulates psychotomimetic-induced deficits in sensorimotor gating

“…Supporting this is the fact that oxytocin binding sites have been identiÞed in the nucleus accumbens (Van Leeuwan 1985), and the Þnding that systemically administered oxytocin blocks the increased dopamine utilization in the nucleus accumbens produced by cocaine (Kovacs et al 1990). It is interesting to note, in light of the present Þndings, the report by Xiao et al (1984) that oxytocin had no e¤ect on hyperlocomotion produced by apomorphine.…”