Prejunctional alpha-adrenoceptors regulate nitrergic neurotransmission in the rabbit urethra.
We evaluated the effects of prejunctional alpha-adrenoceptors on nitric oxide (NO)-mediated urethral relaxation in rabbits using a muscle bath technique and high-performance liquid chromatography coupled with a microdialysis procedure. The amount of NO(2)(-)/NO(3)(-) released during electrical field stimulation was measured by an NO(2)(-)/NO(3)(-) analyzer based on the Griess method. Pretreatment with phenylephrine (0.01 microM) and yohimbine (0.1-10 microM) significantly reduced the relaxation responses induced by electrical field stimulation. In contrast, pretreatment with clonidine (0.01 microM) and prazosin (0.01-1 microM) enhanced the relaxation responses. Cys-NO-induced relaxations of rabbit urethral smooth muscle were not affected by pretreatment with alpha-adrenoceptor agonists and antagonists. The amount of NO(2)(-)/NO(3)(-) released by electrical field stimulation increased after pretreatment with clonidine (0.01 microM) and prazosin (0.01-1 microM), but decreased after pretreatment with phenylephrine (0.01 microM) and yohimbine (0.1-10 microM). The results suggest that the release of NO from nitrergic nerves in the rabbit urethra is reduced and increased by stimulation of prejunctional alpha(1)- and alpha(2)-adrenoceptors, respectively.
Seshita
H
H
Department of Urology, Kumamoto University School of Medicine, 1-1-1 Honjo, 860-8556, Kumamoto, Japan.
Yoshida
M
M
Takahashi
W
W
Inadome
A
A
Yono
M
M
Miyamoto
Y
Y
Murakami
S
S
Ueda
S
S
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology*; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D009573:Nitrites / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D014521:Urethra / Q000187:drug effects / Q000294:innervation*; D015016:Yohimbine / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D019332:Endothelin-1; D009566:Nitrates; D009573:Nitrites; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D015016:Yohimbine; D009569:Nitric Oxide; D011224:Prazosin