Multiple, but not acute, infusions of cocaine alter the release of prolactin in male rats.
Hypothalamic dopamine tonically inhibits the release of prolactin (PRL) from the anterior pituitary gland. Cocaine, in turn, alters dopaminergic transmission. We compared the effects of acute and repeated injections of cocaine on the release of PRL in male rats to assess whether cocaine could affect dopaminergically mediated hormonal responses. We found that the concentration of PRL in plasma was not affected by single i.v. injections of 1, 3 or 10 mg/kg of cocaine. However, in rats infused repeatedly with 1 mg/kg of cocaine for 5 s every 12 min for 2 h over 10 days, the pre-infusion concentrations of PRL increased in a time-dependent manner whereas cocaine uniformly decreased post-infusion levels of PRL. Repeated administration of cocaine may produce long-term changes in either the tuberoinfundibular dopaminergic neurons or the adenohypophysial dopamine D2-receptors, or both. Changes in the peripheral concentration of PRL after multiple injections of cocaine and during cocaine withdrawal may reflect dopaminergic activity in the hypothalamus. In contrast, single injections of cocaine increased adrenocorticotropin (ACTH) in a dose-dependent manner whereas repeated infusions did not increase peripheral concentrations of ACTH or corticosterone. It seems that repeated injections of cocaine do not result in persistent changes in the hypothalamo-pituitary-adrenal axis.
Pilotte
N S
NS
Addiction Research Center, National Institute on Drug Abuse, Baltimore, MD 21224.
Sharpe
L G
LG
Dax
E M
EM
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D003042:Cocaine / Q000008:administration & dosage*; D003345:Corticosterone / Q000097:blood; D004298:Dopamine / Q000378:metabolism / Q000502:physiology*; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D007275:Injections, Intravenous; D008297:Male; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew
D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D003042:Cocaine; D004298:Dopamine; D003345:Corticosterone