Sauvagine-induced hypothermia: evidence for an interaction with the dopaminergic system.
In rats kept at an ambient temperature of 22 degrees C, centrally and peripherally administered sauvagine induces a dose-dependent hypothermia. To clarify the regulatory mechanisms and to ascertain which neurotransmitter systems mediate sauvagine-induced hypothermia, we administered sauvagine intracerebroventricularly and subcutaneously in rats pretreated with antagonists of muscarinic receptors (atropine), opiate receptors (naloxone), alpha-adrenoceptors (phentolamine, yohimbine and prazosin), beta-adrenoceptors (propranolol) and dopamine receptors (haloperidol and spiperone). Systemic pretreatment of rats with atropine, naloxone, prazosin and propranolol left sauvagine-induced hypothermia unaltered. Pretreatment with phentolamine (4 mg/kg, s.c.), a non-selective alpha-adrenoceptor antagonist, and yohimbine (3 mg/kg, s.c.), a selective alpha 2-adrenoceptor antagonist, enhanced the hypothermic action of sauvagine. Pretreatment with haloperidol (2 mg/kg, s.c.), a non-selective dopamine receptor antagonist, and spiperone (80 micrograms/kg, s.c.), a selective dopamine D2 receptor antagonist, significantly reduced the temperature fall induced by centrally (4 micrograms/rat) and peripherally (20 micrograms/kg) administered sauvagine. Thus, sauvagine-induced hypothermia appears not to be mediated by interactions with cholinergic, endogenous opiate or noradrenergic systems, but rather D2 dopaminergic pathways alone are involved in the inhibitory effect of sauvagine on body temperature in the rat.
Broccardo
M
M
Institute of Medical Pharmacology, University La Sapienza, Rome, Italy.
Improta
G
G
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D029845:Amphibian Proteins; D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D065127:Dopamine D2 Receptor Antagonists; D004305:Dose-Response Relationship, Drug; D007035:Hypothermia / Q000139:chemically induced*; D007276:Injections, Intraventricular; D007279:Injections, Subcutaneous; D008297:Male; D018727:Muscarinic Antagonists; D009292:Narcotic Antagonists; D036361:Peptide Hormones; D010455:Peptides / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D017448:Receptors, Dopamine D2 / Q000502:physiology*
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D029845:Amphibian Proteins; D065127:Dopamine D2 Receptor Antagonists; D018727:Muscarinic Antagonists; D009292:Narcotic Antagonists; D036361:Peptide Hormones; D010455:Peptides; D017448:Receptors, Dopamine D2; C025727:sauvagine