title: Elucidation with the protease alpha-chymotrypsin of the inhibitory modulating action of endogenous neuropeptide Y over sympathetic neurotransmission in rat vas deferens.
abstract: The physiological role of endogenous neuropeptide Y (NPY) in sympathetic neurotransmission was examined in rat and guinea pig vas deferens (VD), using alpha-chymotrypsin (alpha-CT). NPY-like immunoreactivity was detected in the longitudinal muscle layer of VD densely in rats but sparsely in guinea pigs, and it disappeared following surgical denervation. Under blockade of the prejunctional alpha(2)-adrenergic autoinhibition, alpha-CT potentiated the phasic contraction in rat, but not guinea pig, VD induced by trains of transmural nerve stimulation (TNS) in a frequency-dependent manner, which was reproducible during repeated applications and not affected by pretreatment with capsaicin. In contrast, alpha-CT did not potentiate the twitch response or contractions induced respectively by a single pulse TNS or by direct electrical stimulation to the smooth muscle. Exogenously applied NPY suppressed the twitch response, which was cancelled by alpha-CT, and excitatory junction potentials, although it affected neither spontaneous junction potentials nor the direct electrical stimulation-induced contraction. These observations provided further evidence to support that NPY is released endogenously by TNS at high frequency, acting prejunctionally to suppress sympathetic neurotransmission. Thus, the protease alpha-CT proved itself to be a useful tool to reveal a functional role of endogenously released peptides.
authors.affiliation: Division of Xenobiotic Metabolism and Disposition, National Institute of Health Sciences, Tokyo, Japan. kono@nihs.go.jp
authors.forename: Kageyoshi
authors.initials: K
authors.lastname: Ono
authors.forename: Akira
authors.initials: A
authors.lastname: Saito
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Goto
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kasuya
authors.forename: Koki
authors.initials: K
authors.lastname: Shigenobu
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D002918:Chymotrypsin; D003714:Denervation; D004558:Electric Stimulation; D004594:Electrophysiology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D009411:Nerve Endings / Q000378:metabolism; D009478:Neuropeptide Y / Q000494:pharmacology / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D014649:Vas Deferens / Q000187:drug effects / Q000294:innervation / Q000502:physiology
chemical_list: D009478:Neuropeptide Y; D018377:Neurotransmitter Agents; D002918:Chymotrypsin; D002118:Calcium