5-HT-(1D) receptor inhibits renal sympathetic neurotransmission by nitric oxide pathway in anesthetized rats

摘要

Although serotonin has been shown to inhibit peripheral sympathetic outflow, serotonin regulation on renal sympathetic outflow has not yet been elucidated. This study investigated which 5-HT receptor subtypes are involved. Wistar rats were anesthetized (sodium pentobarbital; 60 mg/kg, i.p.), and prepared for in situ autoperfused rat kidney, which allows continuous measurement of systemic blood pressure (SBP), heart rate (HR) and renal perfusion pressure (PP). Electrical stimulation of renal sympathetic nerves resulted in frequency-dependent increases in PP (18.3 +/- 1.0, 43.7 +/- 2.7 and 66.7 +/- 4.0 for 2,4 and 6 Hz, respectively), without altering SBP or HR. 5-HT, 5-carboxamidotryptamine (5-HT1/7 agonist) (0.00000125-0.1 mu g/kg each) or L-694,247 (5-HT1D agonist; 0.0125 mu g/kg) i.a. bolus inhibited vasopressor responses by renal nerve electrical stimulation, unlike i.a. bolus of agonists alpha-methyl-5-HT (5-HT2), 1-PBG (5-HT3), cisapride (5-HT4), AS-19 (5-HT7), CGS-12066B (5-HT1B) or 8-OH-DPAT (5-HT1A) (0.0125 mu g/kg each). The effect of L-694,247 did not affect the exogenous norepinephrine-induced vasoconstrictions, whereas was abolished by antagonist LY310762 (5-HT1D; 1 mg/kg) or L-NAME (nitric oxide; 10 mg/kg), but not by indomethacin (COX1/2; 2 mg/kg) or glibenclamide (ATP-dependent K+ channel; 20 mg/kg). These results suggest that 5-HT mechanism-induced inhibition of rat vasopressor renal sympathetic outflow is mainly mediated by prejunctional 5-HT1D receptors via nitric oxide release. (C) 2015 Elsevier Inc. All rights reserved.