Activation of brown adipose tissue thermogenesis by chemical stimulation of the hypothalamic supraoptic nucleus.
Glutamate microinjection (1 M, 250 nl) into the hypothalamic supraoptic nucleus (SON) stimulated heat production in brown adipose tissue (BAT) and caused a rapid and sustained increase in interscapular BAT and core temperatures in urethane-anaesthetized rats. This effect was blocked by intraperitoneal pretreatment with a sympathetic ganglionic blocker, chlorisondamine chloride (2.5 mg/kg), or a beta-adrenergic receptor blocker, propranolol (2.5 mg/kg), but not by prior hypophysectomy or intracerebroventricular pretreatment with specific receptor blockers to vasopressin (d(CH2)5[Tyr(Me)2]AVP, 5 micrograms) or oxytocin (d(CH2(5)[Tyr(Me)2,Thr4,Tyr-NH2(9)]OVT, 5 micrograms). The results demonstrate that stimulation of SON cells with glutamate elicits a non-vasopressinergic/non-oxytocinergic neural signal that can bring about a sympathetically-mediated increase in BAT thermogenesis. Heat production in BAT is an important mechanism of thermal protection during cold stimulation, and there is evidence that osmotic stimulation can influence thermoregulation. SON neurons play a major role in osmoregulation via release of the peptide hormones vasopressin and oxytocin. The present results suggest the possibility that apart from releasing peptide hormones for osmoregulation, SON neurons might be involved in mediating the effect of osmotic stimulation on thermoregulatory responses involved in thermal adaptation.
Department of Psychology, Concordia University, Montreal, Que., Canada.
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Amir
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De Blasio
D002001:Adipose Tissue, Brown / Q000502:physiology*; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects / Q000502:physiology*; D002714:Chlorisondamine / Q000008:administration & dosage / Q000494:pharmacology; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D008845:Microinjections; D009474:Neurons / Q000502:physiology; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology; D010121:Oxytocin / Q000378:metabolism; D051381:Rats; D013238:Stereotaxic Techniques; D013268:Stimulation, Chemical; D013495:Supraoptic Nucleus / Q000187:drug effects / Q000502:physiology*; D014667:Vasopressins / Q000037:antagonists & inhibitors / Q000378:metabolism
D000319:Adrenergic beta-Antagonists; D005971:Glutamates; D014667:Vasopressins; D018698:Glutamic Acid; D010121:Oxytocin; D002714:Chlorisondamine; D009638:Norepinephrine