Development of tolerance to the hormonal effects of morphine without changes in the aminergic functions in the brain of the rat.
The effect of morphine on cold-stimulated secretion of TSH and prolactin was studied in male rats, both in acute studies and after the chronic administration of morphine for 14 days (twice a day with increasing doses). The duration of the stimulatory effect of a single dose of morphine on secretion of prolactin was shorter (less than 2 hr) than its inhibitory effect on cold-stimulated secretion of TSH (over 2 hr). In the rats pretreated with morphine, a tolerance to the depressant effect of TSH of the challenge dose of morphine was seen at 2 hr but not at 1 hr after the injection. In contrast, a tolerance to the stimulatory effect of morphine on prolactin was seen at 1 hr after the acute dose of morphine. The minor alterations of the hypothalamic amine neurotransmitters and their metabolites did not correlate with the hormonal responses or to the development of tolerance.
Rauhala
P
P
Department of Pharmacology and Toxicology, University of Helsinki, Finland.
Tuominen
R K
RK
Tuomainen
P
P
Toivonen
M
M
Borisenko
S A
SA
Männisto
P T
PT
D000818:Animals; D015306:Biogenic Monoamines / Q000378:metabolism*; D001923:Brain Chemistry / Q000187:drug effects*; D003080:Cold Temperature; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D006728:Hormones / Q000097:blood*; D007031:Hypothalamus / Q000378:metabolism; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D011388:Prolactin / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D013972:Thyrotropin / Q000097:blood; D013997:Time Factors
D015306:Biogenic Monoamines; D006728:Hormones; D009020:Morphine; D011388:Prolactin; D013972:Thyrotropin