Blood pressure and heart rate responses to centrally administered substance P are increased in spontaneously hypertensive rats.
1. The cardiovascular effects after intracerebroventricular injections of substance P were investigated in normotensive Wistar-Kyoto and in spontaneously hypertensive rats. 2. Substance P increased blood pressor in both rat strains. Wistar-Kyoto rats responded with moderate, dose-dependent blood pressure increases, and heart rate decreased; spontaneously hypertensive rats showed two- to three-fold increased pressor effects and, concomitantly, marked heart rate increases to intracerebroventricular injections of substance P. 3. Sino-aortic baroreceptor denervation rendered Wistar-Kyoto rats supersensitive to intracerebroventricular substance P to a similar degree as unoperated spontaneously hypertensive rats. Sino-aortic denervation had no effect on the blood pressure responses to the peptide in spontaneously hypertensive rats. 4. The central pressure actions of substance P could be markedly attenuated by intracerebroventricular pretreatment with the derivative of gamma-aminobutyric acid, baclofen. 5. We conclude that the baroreceptor reflex is disturbed in spontaneously hypertensive rats. Substance P may contribute to the pathogenesis of hypertension. The effector pathways appear to be different from angiotensin.
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects*; D003714:Denervation; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006973:Hypertension / Q000503:physiopathology*; D007276:Injections, Intraventricular; D008297:Male; D011311:Pressoreceptors / Q000502:physiology; D051381:Rats; D013373:Substance P / Q000008:administration & dosage / Q000494:pharmacology*
D000804:Angiotensin II; D013373:Substance P; D001418:Baclofen