Dipsogenic-like and behavioural effects of bombesin administered intracerebroventricularly to sheep.

Bombesin administered intracerebroventricularly both by bolus injection (3.0, 6.0, 12.5, 25.0 and 50.0 ng kg-1) and slow infusion (0.4, 0.8 and 1.6 ng kg-1 min-1 for 30 min) potently and promptly stimulated water intake in sheep. This effect was dose dependent and bombesin was slightly more potent than angiotensin II (on a molar basis); both caused behavioural alterations (scratching and licking) in treated animals. Intravenous bolus injections of bombesin at doses up to 2500 ng kg-1 did not elicit either dipsogenic-like or behavioural effects, unlike angiotensin II. The receptor antagonist of angiotensin II, saralasin, provoked drinking in sheep at doses of 18.7, 37.5 and 75.0 ng kg-1 by intracerebroventricular bolus injection. These results surprisingly revealed that bombesin, a potent inhibitor of water intake in other mammals (rats and pigs), exerted in sheep dipsogenic-like effects similar to those in pigeons and ducks.

Possible mechanisms of action of caerulein on intestinal motility of sheep.

The authors report the stimulatory effects provoked by caerulein on caecum and colon motilities in sheep which are quite opposite to those exerted by the same peptide on the forestomach and abomasal sections. By means of various pharmacological tools these effects are suggested to be attributable to a direct effect of caerulein on the smooth muscle of these viscera through the involvement of receptors different from those ones on which CCK may be antagonizable by proglumide or cGMP pretreatments.