title: Neuroendocrine effects of caffeine. II. Effects on thyrotropin and corticosterone secretion.
abstract: Caffeine injected i.p. to rats decreased serum thyrotropin and markedly increased serum corticosterone with ED50 values of 40 to 50 mg/kg. Adrenalectomy did not affect the response of thyrotropin to caffeine. Theophylline was as potent as caffeine in inhibiting thyrotropin and stimulating corticosterone secretion; theobromine and paraxanthine were less potent, but their own serum concentrations were also lower. One week of once-daily injections of 50 mg/kg of caffeine produced tolerance to its effects on thyrotropin and corticosterone. The lowest caffeine dose to produce tolerance to a 50-mg/kg challenge dose was 25 mg/kg. Adenosine receptor agonists did not affect serum thyrotropin nor did they block the caffeine-induced decrease in serum thyrotropin. Blockade of the hypothermic effect of caffeine did not alter the effect of caffeine on serum thyrotropin. Similarly, the caffeine-induced decrease in serum thyrotropin was additive to the decrease produced by placing rats in a warm environment or to the increase in serum thyrotropin produced by placing them in the cold. Deviating from the stress-like pattern of increased corticosterone and decreased thyrotropin, caffeine did not affect prolactin secretion in ovariectomized rats with or without estrogen pretreatment.
mesh_terms: D000315:Adrenalectomy; D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D002110:Caffeine / Q000008:administration & dosage* / Q000494:pharmacology; D003345:Corticosterone / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D005260:Female; D007035:Hypothermia / Q000139:chemically induced; D009490:Neurosecretory Systems / Q000187:drug effects; D011388:Prolactin / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000187:drug effects; D011983:Receptors, Purinergic; D013972:Thyrotropin / Q000097:blood*
chemical_list: D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; D002110:Caffeine; D011388:Prolactin; D013972:Thyrotropin; D003345:Corticosterone