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Increased blood pressure (BP) in genetic hypertension is usually caused by high activity of sympathetic nervous system (SNS) which is enhanced by central angiotensin II but lowered by central nitric oxide (NO). We have therefore evaluated NO synthase (NOS) activity as well as neuronal NOS (nNOS), inducible NOS (iNOS) and endothelial NOS (eNOS) protein expression in brainstem and midbrain of adult spontaneously hypertensive rats (SHR) characterized by enhanced sympathetic vasoconstriction. We also studied possible participation of brain NO in antihypertensive effects of chronic captopril treatment of adult SHR. NOS activity was increased in midbrain of SHR compared to Wistar-Kyoto (WKY) rats. This could be ascribed to enhanced iNOS expression, whereas nNOS expression was unchanged and eNOS expression was reduced in this brain region. In contrast, no significant changes of NOS activity were found in brainstem of SHR in which nNOS and iNOS expression was unchanged, but eNOS expression was increased. Chronic captopril administration lowered BP of adult SHR mainly by attenuation of sympathetic tone, whereas the reduction of angiotensin II-dependent vasoconstriction and the decrease of residual BP (amelioration of structural remodeling of resistance vessels) were less important. This treatment did not affect significantly either NOS activity or expression of any NOS isoform in the two brain regions. Our data do not support the hypothesis that altered brain NO formation contributes to sympathetic hyperactivity and high BP of adult SHR with established hypertension.

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The effects of the peptidergic nootropic drug Cerebrolysin on spatial memory and motor activity were examined in intact and ischemic rats. Ischemic-hypoxic damage was induced by injection of Na-cyanide followed by bilateral occlusion of common carotid arteries. Immediately afterwards Cerebrolysin or saline was administered, either by continuous intraventricular (i.v.) infusion or by daily intraperitoneal (i.p.) injection. Rats were tested for spatial memory and motor activity in the Morris water maze on days 3 and 4 post-surgery. The best dose of the substance for i.p. administration was known from previous studies. Therefore we had to investigate the dose-response-relationship and tolerability of the drug after i.v. administration in intact rats. Infusion (i.v.) of a high dose of Cerebrolysin (0.57 mg/day) decreased motor activity and spatial memory of intact rats (p < 0.01 and p < 0.05, respectively) but low dose of Cerebrolysin was well tolerated in the intact animals. Ischemia led to deterioration of motor activity in control rats (p < 0.01). Cerebrolysin significantly counteracted deleterious motor changes due to ischemia up to the level of intact controls after both i.v. infusion (0.0057 mg/day) and daily i.p. drug administration (100 mg/kg bw and day) indicating an accelerating recovery after ischemia.

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