Effects of intraventricular neurotensin on blood pressure and heat balance in rats.

Abstract

The effects of intraventricular neurotensin (NT) at doses of 0.1, 1.0, and 10.0 µg on blood pressure (BP), heart rate (HR), heat production (M), heat loss (H), and colonic temperature (Tco1) were investigated in conscious rats in a direct calorimeter at 18 and 28°C. At 18°C, a 10.0 ,ug of NT significantly increased BP for several minutes after injection with prolonged bradycardia. The larger two doses (1.0 and 10.0 ,ug) significantly reduced M and Tco1. In sinoaortic denervated rats, a 1.0 ,ug of NT elevated BP and decreased HR. The decrease in HR was significantly smaller than that in nerve intact rats, which indicates the occurrence of baroreflex with Intraventricular NT. The changes in M and Tco1 in the denervated rats were, however, not statistically different from the intact rats. The barorefiexive suppression of metabolism seems to play a minimum role in the NT-induced hypothermia. H slightly increased for several minutes after central NT (1.0 and 10.0 ,ug) and significantly decreased thereafter. Thermal conductance significantly increased for a longer period of time after NT injection. At 28°C, 1.0 ,ug of NT increased H and M. It is concluded that central NT produced hypothermia by reducing M and enhancing H in the cool environment, but not at 28°C.

Carotid-Sinus Baroreflex Modulation of Core and Skin Temperatures in Rats: An Open-Loop Approach

“…Earlier studies investigated the effect of the arterial baroreflex on body temperatures under the closedloop conditions of the arterial baroreflex [18][19][20]. However, vasoactive agents used in these studies for loading or unloading the arterial baroreceptors could directly, i.e., not mediated by the arterial baroreflex, affect the distribution of cardiac output.…”

“…Therefore it would be difficult to directly link the baroreceptor unloading to the resultant decrease in skin blood flow and temperature, because the decrease in cardiac output itself can directly modulate skin circulation. It is also difficult to evaluate the role of the arterial baroreceptor reflex in thermoregulation from the responses of core and skin temperatures to pharmacological changes in arterial pressure [18][19][20] because the systemic administration of vasoactive agents itself could affect the distribution of cardiac output to various organs, including the skin. Along with thermoregulation, the baroreflex control of arterial pressure is a physiological feedback system.…”

Orexigenic vs. anorexigenic peptides and feeding status in the modulation of fever and hypothermia

“…they do not exert such coordinated effects on consummatory behavior and metabolic rate. For example, bombesin (21) or neurotensin (22) suppresses both food intake and metabolic rate (i.e. they are anorectic, but not catabolic), unlike the catabolic melanocortin or leptin, both of which cause hypermetabolism simultaneously suppressing food intake (23,24), or the anabolic neuropeptide Y, which suppresses metabolic rate concurrently enhancing food intake (24).…”