Presynaptic serotonin receptors on peripheral noradrenergic and central serotoninergic neurons of spontaneously hypertensive and Wistar-Kyoto rats.

In spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats it was examined whether the effects mediated by presynaptic 5-HT1 receptors on noradrenergic and serotoninergic neurons are altered in hypertension. Vascular strips (arteria iliaca, vena cava) as well as brain slices (nucleus tractus solitarii, hypothalamus, cortex) were prepared from 5-7-, 9-11-, and 19-22-week-old SHR and WKY rats (mean systolic blood pressure: 111, 183, and 212 and 105, 113, and 106 mm Hg, respectively). Subsequent to incubation with [3H]noradrenaline ([3H]NA; vascular strips) and [3H]serotonin ([3H]5-HT; brain slices), the tissues were superfused and the effects of 5-HT on the electrically evoked [3H]monoamine overflow were studied. The inhibitory effect of 5-HT on the evoked [3H]NA release in the arterial strips did not differ between both strains (at any age). In strips of the vena cava, the maximum inhibitory effect of 5-HT on evoked release was, at any age, more pronounced in SHR than in WKY rats. In slices of the three brain regions, the evoked [3H]5-HT release was similar in SHR and WKY rats. Likewise, the inhibitory effect of 5-HT on the evoked release did not differ in both strains at any age. The present results indicate that the inhibitory effect mediated by presynaptic 5-HT1 receptors is more pronounced in the vein, but is identical in the artery, of SHR rats compared to WKY rats. 5-HT release in the brain and its modulation via inhibitory presynaptic 5-HT1 autoreceptors do not differ in both strains.(ABSTRACT TRUNCATED AT 250 WORDS)