Calcium Handling in Postganglionic Sympathetic Neurons is enhanced in Prehypertensive Spontaneously Hypertensive rat

Abstract

Noradrenergic hyperactivity is associated with hypertension that may precede the developing of hypertension itself. We hypothesized that Ca2+ signalling in sympathetic neurons is enhanced in young pre‐hypertensive spontaneously hypertensive rats (SHR). We measured depolarisation (high [K+]0) evoked Ca2+ transient ([Ca2+]i) with fluorescence imaging using fura‐2 in superior cervical ganglia from age and gender matched hypertensive and normotensive Wistar‐Kyoto (WKY) rats. In 4‐7 day old rats, no difference was observed in [Ca2+]i between the SHR and WKY. In contrast, among young pre‐hypertensive (4‐5 weeks old) rats, [Ca2+]i were higher in the SHR (male: 1.39±0.11 μM; female: 1.21±0.05 μM) compared with the gender matched WKY (male: 1.08±0.13 μM, p<0.05; female: 1.07±0.05 μM, p<0.05). In adult (16‐18 weeks old) rats the [Ca2+]i were also increased in the SHR (male: 1.82±0.06 μM; female: 1.58±0.07 μM) compared with the gender matched WKY (male: 1.59±0.09 μM, p<0.01; female: 1.12±0.06 µM, p<0.001). Interestingly, in the adult SHR and WKY, [Ca2+]i was significantly higher in male. The overall responses are consistent with the hypothesis that enhanced Ca2+ signalling may contribute to the noradrenergic hyperactivity that is seen before the onset of hypertension itself.This work was supported by British Heart Foundation and Welcome Trust.