Neuropeptide Abnormalities Suggest a Dopaminergic Basis for High Blood Pressure in the Spontaneously Hypertensive Rat

Abstract

The spontaneously hypertensive rat (SHR) and the stroke-prone substrain (sp-SHR) have been reported to have several abnormalities in levels of peptides both in tissue and in plasma (beta-endorphin, prolactin, thyroid stimulating hormone and vasopressin) when compared to the Wistar Kyoto (WKY) normotensive control rat. As the secretion of these peptides is under dopaminergic control and the abnormalities consistently suggest under-activity of the dopaminergic control system in the brain, injections of dopamine (0.4 mg/kg) were given i.c.v. to 10 SHR, 10 renal artery stenosis hypertensive rats (LRAS) and 10 genetically hypertensive rats of the New Zealand strain (GHR). Mean blood pressure fell from 205 +/- 6 (SEM) mmHg to 128 +/- 8 mmHg in the SHR (p less than 0.001), from 184 +/- 7 mmHg to 176 +/- 7 mmHg in the LRAS (p greater 0.05) and from 157 +/- 5 mmHg to 138 +/- 6 mmHg in he GHR (p less than 0.02). These effects were unlikely to be due to leakage of dopamine out into the periphery as i.v. dopamine (0.4 mg/kg) increased blood pressure in these animals.

Blood Pressure, Plasma and Pituitary Prolactin Responses to Bromocriptine in New Zealand Genetically Hypertensive and Normotensive Rats

“…The GHR, on the other hand, has been shown to have increased sympathetic tone (Clark & Phelan 1976) and increased peripheral vascular resistance (Simpson & Phelan 1984) compared with the normotensive (NT) rats. Previous work in this laboratory (Hutchinson & Mok 1984) showed that acute intracerebroventricular (i.c.v.) administration of dopamine to anaesthetized SHR and GHR produced significant falls in mean blood pressure (BP) in both strains.…”