Chronic serotonin infusion leads to prolonged fall in blood pressure in the spontaneously hypertensive rat

Abstract

Chronic serotonin, or 5‐hydroxytryptamine (5‐HT) infusion results in a prolonged fall in blood pressure (BP) in the deoxycorticosterone acetate (DOCA)‐salt hypertensive model. The role of 5‐HT in BP regulation and hypertension remains largely unknown. To further our understanding of the hypotensive role of 5‐HT, we investigated chronic 5‐HT infusion in the spontaneously hypertensive rat (SHR). We hypothesized that 5‐HT infusion in SHR would result in a fall in BP when compared with DOCA‐salt model. 5‐HT and Vehicle (Veh) were administered subcutaneously via osmotic pump (25μg/kg/min) for 7 days to 14 week old male SHR. Free circulating plasma 5‐HT levels increased in both SHR and DOCA model with 5‐HT infusion. Platelet poor plasma levels (PPP) were higher in the 5‐HT‐infused SHR (23.1± 16.2 ng/ml), compared with Veh‐infused SHR (0.33 ± 0.1 ng/ml). PPP levels were also higher in 5‐HT‐infused DOCA (114.5 ± 21.1 ng/ml), compared with Veh‐infused DOCA (24.9 ± 5.0 ng/ml). Mean arterial BP was monitored via radiotelemetry. Resting SHR BP was 145± 1.61 mmHg, while DOCA BP was 166 ± 7.58 mmHg. After 24 hours of 5‐HT infusion, SHR BP fell to 111 ± 2.45 mmHg, while DOCA pressure fell to 139 ± 3.15 mmHg. This study demonstrates a similar hypotensive role for 5‐HT in the SHR compared to DOCA and a potentially beneficial role for 5‐HT in cardiovascular system. This is the first study to investigate chronic 5‐HT‐infusion in the SHR model.