HYPOTENSIVE EFFECT OF DIAZEPAM IN SPONTANEOUSLY HYPERTENSIVE RATS (SHR)

Abstract

To test if hypertension in SHR is related to exaggerated central responsiveness to environment, Diazepam (D) was chronically administered from the newborn period to adulthood. Four groups (10 each) were studied receiving either daily D 0.02 mg/gm S.C. or D vehicle (V): (1) SHR-D; (2) SHR-V; (3) normotensive control (NC-D); (4) NC-V. Tailcuff blood pressure was consistently 20-30 mm Hg lower in SHR-D than SHR-V (p<.01). Blood pressure of NC-D and NC-V were similar. Pulse rate was similar. Vasomotor reactivity was studied at 12 weeks by hindquarter vascular resistance. Though SHR-V developed high vascular resistance (VR), VR in SHR-D was reduced (p<.05), the VR of NC-D and NC-V were similar. The change in vascular resistance to norepinephrine (NE), epinephrine (E), barium chloride (BaCl2), angiotensin (Ang) and acetycholine (ACH) are summarized below: (*p<.05;]not significantly different) Response to lumbar sympathetic stimulation was blunted in SHR-D. Conclusions: D, by peripheral and or central mechanisms depresses vascular smooth muscle reactivity to a wide variety of stimuli, however these effects are related to a hypotenslve action only in SHR.