Responses of anterior pituitary hormones and hypothalamic histamine to blockade of histamine synthesis and to selective activation or inactivation of presynaptic histamine H3 receptors in stressed rats.
The stress-induced release of anterior pituitary hormones and changes in hypothalamic content of histamine (HA) and its metabolite tele-methylHA (t-meHA) were studied in male rats during inhibition of HA synthesis or activation or blockade of HA H3 receptors. Pretreatment with the HA synthesis inhibitor alpha-fluoromethylhistidine (alpha-FMH; 200 micrograms intracerebroventricularly (icv) at -120 min) or the specific H3 receptor agonist R(alpha)methylhistamine (RmHA; 10 mg/kg intraperitoneally (ip) at -180 and -60 min) inhibited by 30-80% the responses of prolactin (PRL), corticotropin (ACTH) and beta-endorphin (beta-END) immunoreactivity to 1, 2.5 or 5 min of restraint stress (p < 0.05-0.01), but had no effect on basal secretion of the hormones. The inhibitory effect of the H3 receptor agonist RmHA (10 mg/kg x 2) on the hormone response to 5 min of restraint stress was prevented by simultaneous ip administration of the H3 receptor antagonist thioperamide. alpha-FMH reduced the hypothalamic content of HA 60% and that of t-meHA 30%, while RmHA had no effect on the HA content. Restraint stress for 5 min did not affect the HA and t-meHA contents, which may be due to the short duration of stress exposure. Pretreatment with the H3 receptor antagonist thioperamide (5 or 10 mg/kg ip at -120 min) had no effect on basal or restraint stress-induced release of PRL, ACTH or beta-END, although the compound increased the hypothalamic content of t-meHA 2-fold.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
P
P
Søe-Jensen
U
U
Knigge
M
M
Garbarg
A
A
Kjaer
A
A
Rouleau
F W
FW
Bach
J C
JC
Schwartz
J
J
Warberg
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D006632:Histamine / Q000096:biosynthesis / Q000378:metabolism*; D006633:Histamine Antagonists; D007003:Hypoglycemia / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008761:Methylhistamines / Q000494:pharmacology; D008762:Methylhistidines / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D010908:Pituitary Hormones, Anterior / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011968:Receptors, Histamine / Q000502:physiology*; D018100:Receptors, Histamine H3; D012149:Restraint, Physical; D013312:Stress, Physiological / Q000503:physiopathology*; D001615:beta-Endorphin / Q000378:metabolism
D006633:Histamine Antagonists; D007328:Insulin; D008761:Methylhistamines; D008762:Methylhistidines; D010880:Piperidines; D010908:Pituitary Hormones, Anterior; D011968:Receptors, Histamine; D018100:Receptors, Histamine H3; D001615:beta-Endorphin; C069357:alpha-methylhistamine; C028309:alpha-fluoromethylhistidine; D006632:Histamine; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; C052075:thioperamide