Role of supraspinal vasopressin neurones in the effects of atrial natriuretic peptide on sympathetic nerve activity.
The aim of the present study was to determine if paraventricular-spinal vasopressin neurones participate in the sympatho-inhibitory effects of systemically administered atrial natriuretic peptide (ANP) on renal sympathetic nerve activity (RSNA). Experiments were carried out on male Sprague-Dawley rats anesthetized with 1.3 g/kg urethane. Changes in mean arterial pressure (mm Hg), heart rate (beats per minute) and RSNA (%) were measured following intravenous bolus administration of ANP (250 ng, 500 ng and 5 microg). Intrathecal application of selective V 1a receptor antagonist was performed to test for the involvement of supraspinal vasopressin pathways in mediating the effect on sympathetic outflow evoked by intravenous ANP administration. The results obtained demonstrated that both low and high doses of ANP caused renal sympathoinhibition (250 ng; - 7.5 +/- 1%, 500 ng; - 14.2 +/- 1%, 5 microg; - 16.4 +/- 2%), concomitant with vasodilation and bradycardia. After spinal vasopressin receptor blockade, the inhibitory effects of ANP were prevented and there was a small renal sympatho-excitation (250 ng; + 1.7 +/- 0.2%, 500 ng; + 6.1 +/- 0.03%, 5 microg; + 8.0 +/- 0.03%, P < 0.05). Therefore, the renal sympathetic nerve inhibition elicited by circulating ANP is dependent on the efficacy of a well established supraspinal vasopressin pathway. Since supraspinal vasopressin neurones without exception excite renal sympathetic neurones, it is suggested that ANP elicits this effect by activating cardiac vagal afferents that inhibit the spinally projecting vasopressin neurones at their origin in the paraventricular nucleus of the hypothalamus.
Masterskill University College Of Health Sciences (MUCH), Main Campus, Kemacahaya Street, 9th Mile, 43200, Cheras, Selangor Darul Ehsan, Malaysia. ahmadpauzi@masterskill.edu.my
A P M
AP
Yusof
N H M
NH
Yusoff
F W
FW
Suhaimi
J H
JH
Coote
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D065092:Antidiuretic Hormone Receptor Antagonists; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007668:Kidney / Q000294:innervation; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000166:cytology*; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000502:physiology; D014667:Vasopressins / Q000378:metabolism*
D065092:Antidiuretic Hormone Receptor Antagonists; D014667:Vasopressins; D009320:Atrial Natriuretic Factor