Hypothermia and intolerance to cold induced by intracisternal administration of the hypothalamic peptide neurotensin

Abstract

NEUROTENSIN is a tridecapeptide (pGlu–Leu–Tyr–Glu–Asn–Lys–Pro–Arg–Arg–Pro–Tyr–Ile–Leu–COOH)¹ isolated from bovine hypothalami². Using a sensitive and specific radio immunoassay, Carraway and Leeman have demonstrated immunoreactive neurotensin in hypothalamic extracts of rat, mouse, rabbit and human tissue³. Intravenous (i.v.) administration of neurotensin to rats has been reported to cause hypotension (minimum effective dose 100 pmol kg⁻¹ = 0.167 µg kg⁻¹), cyanosis (minimum effective dose 1 nmol kg⁻¹ = 1.67 µg kg⁻¹)², and hyperglycaemia (minimum effective dose 200 pmol kg⁻¹ = 0.33 µg kg⁻¹)⁴. These effects are not prevented by adrenalectomy or hypophysectomy. The hypotensive effects are not altered by α- or β-adrenergic blockers. Neurotensin also stimulates the contraction of guinea pig ileum while relaxing rat duodenum in vitro. Neurotensin is as potent as bradykinin in its effects on guinea pig ileum and rat duodenum and thus is classified as a kinin². It increases plasma gonadotropin levels in ovariectomised, oestrogen–progesterone-treated rats after intravenous injection (minimum effective dose 5 nmol kg⁻¹ = 8.4 µg kg⁻¹)⁵. Intravenous administration of a dose of 3 µg kg⁻¹ to rats produces hypoinsulinaemia, hyperglycaemia and hyperglucagonaemia⁶.