Abstract
The intravenous injection of neurotensin (NT) (0.4 and 1.1 nmoles/kg) produced dose-dependent hypotensive effects in pentobarbital anesthetized rats. The acute or chronic administration of compound 48/80, a well known mast cell depletor, completely abolished the hypotensive effect of low to medium doses of NT and unmasked the previously unknown hypertensive effect of high doses (4.0 nmoles/kg) of NT. This hypertensive effect was significantly reduced by infusing the animals with [D-Trp 11]-NT a selective antagonist of NT. The hypotensive action of NT in control rats was also significantly reduced by pretreating the animals with disodium cromoglycate, an antiallergic drug which is believed to stabilize mast cells membranes, or with a mixture of azatadine and methysergide. The results suggest the participation of histamine, serotonin and possibly other endogenous vasoactive substances, to the hypotensive action of NT in rats. The possible origin of these mediators is discussed.
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