EFFECT OF THE NEUROTENSIN RECEPTOR ANTAGONIST SR48692 ON RAT-BLOOD PRESSURE MODULATION BY NEUROTENSIN

When administered as an intravenous injection in the pentobarbitone-an aesthetized rat, neurotensin (NT) elicits a biphasic depressor-presser effect that can be evaluated by the mean arterial blood pressure (MAB P). The first hypotensive phase elicited by low doses of NT is depende nt on the interaction of NT with its specific receptors and may be med iated by the release of histamine, since it is prevented by oral pretr eatment with the selective NT receptor antagonist SR 48692 and by intr avenous pretreatment with a selective H-1 receptor antagonist mepyrami ne. The hypertensive effect evoked by higher doses of NT is histamine- independent but remains NT receptor-mediated. The prevention of the bi phasic effect on MABP by oral administration of the NT receptor antago nist SR 48692 validates the implication of NT receptors in the histami ne release phenomenon.