Altered function of nitrergic nerves inhibiting sympathetic neurotransmission in mesenteric vascular beds of renovascular hypertensive rats.
Neuronal nitric oxide (NO) has been shown to modulate perivascular adrenergic neurotransmission by inhibiting noradrenaline release from terminals in rat mesenteric arteries. This study was conducted to investigate changes in the inhibitory function of NO-containing nerves (nitrergic nerves) in mesenteric vascular beds of 2-kidney, 1-clip renovascular hypertensive rats (2K1C-RHR). Rat mesenteric vascular beds without endothelium were perfused with Krebs solution and the perfusion pressure was measured. In preparations from sham-operated rats (control) and 2K1C-RHRs, vasoconstriction induced by periarterial nerve stimulation (PNS; 2-8 Hz), but not vasoconstriction induced by exogenously injected noradrenaline (0.5, 1.0 nmol), was markedly facilitated in the presence of a nonselective NO synthase (NOS) inhibitor, N-omega-nitro-L-arginine methyl ester (L-NAME) (100 microM). The facilitatory effect of L-NAME in preparations from 2K1C-RHR was smaller than that in control preparations. L-NAME augmented PNS-evoked noradrenaline release, which was smaller in 2K1C-RHRs than in controls. The expression of neuronal NO synthase (nNOS) measured by western blotting in mesenteric arteries from 2K1C-RHRs was significantly decreased compared with control arteries. Immunohistochemical staining of mesenteric arteries showed dense innervation of nNOS-immunopositive nerves that was significantly smaller in arteries from 2K1C-RHR than that in control arteries. Mesenteric arteries were densely innervated by tyrosine hydroxylase-immunopositive nerves, which coalesced with nNOS-immunopositive nerves. These results suggest that the inhibitory function of nitrergic nerves in adrenergic neurotransmission is significantly decreased in 2K1C-RHRs. This functional alteration based on the decrease in nNOS expression and nitrergic innervation leads to enhanced adrenergic neurotransmission and contributes to the initiation and development of renovascular hypertension.
Koyama
Toshihiro
T
Department of Clinical and Pharmaceutical Science, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Tsushima-naka, Okayama, Japan.
Hatanaka
Yukako
Y
Jin
Xin
X
Yokomizo
Ayako
A
Fujiwara
Hidetoshi
H
Goda
Mitsuhiro
M
Hobara
Narumi
N
Zamami
Yoshito
Y
Kitamura
Yoshihisa
Y
Kawasaki
Hiromu
H
D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D006977:Hypertension, Renal / Q000378:metabolism / Q000503:physiopathology*; D007150:Immunohistochemistry; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism / Q000503:physiopathology*; D018613:Microscopy, Confocal; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D026602:Nitrergic Neurons / Q000187:drug effects / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000187:drug effects
D052248:Nitric Oxide Synthase Type I; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine