A comparison between the hypothermia induced by intra-ventricular injections of thyrotropin releasing hormone, noradrenaline or calcium ions in unanaesthetized cats.
1 The hypothermia produced by intraventricular injections of thyrotropin releasing hormone (TRH) in unanaesthetized cats has been investigated. 2 TRH is more potent than either noradrenaline or calcium ions. It is estimated that the equi-potent molar ratio for TRH: noradrenaline:calcium is 1:900:27,000. 3 TRH injections is also produce profuse salivation, tachypnoea, cutaneous vasodilatation and frequently defaecation and vomiting. It is considered that the increased respiration is a major cause of the hypothermia. 4 Prior administration of phentolamine antagonized noradrenaline-induced hypothermia but did not affect hypothermia produced by TRH or calcium ions. Pretreatment with alpha-methyltyrosine did not affect the hypothermia induced by TRH, calcium ions or noradrenaline. 5 The calcium antagonists verapamil and xylocaine did not antagonize hypothermia induced by an injection of calcium ions. 6 The constituent amino acids of TRH did not produce hypothermia either individually or collectively. Thyroxine sodium produced a rise in temperature that was slow in onset, consistent with its known metabolic effects. TSH produced a small hypothermia unrelated to dose.
D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D002118:Calcium / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002415:Cats; D005260:Female; D006639:Histidine / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D008781:Methyltyrosines / Q000494:pharmacology; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D011392:Proline / Q000494:pharmacology; D011761:Pyrrolidonecarboxylic Acid / Q000494:pharmacology; D012119:Respiration / Q000187:drug effects; D013972:Thyrotropin / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D013974:Thyroxine / Q000494:pharmacology; D013997:Time Factors
D008781:Methyltyrosines; D006639:Histidine; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D011392:Proline; D013974:Thyroxine; D002118:Calcium; D011761:Pyrrolidonecarboxylic Acid; D009638:Norepinephrine; D010646:Phentolamine