Muscarinic Receptor Induced Contractions of the Detrusor are Mediated by Activation of TRPC4 Channels

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• 作者：Caoimhin S. Griffin ; Eamonn Bradley ; Srikanth Dudem ; Mark A. Hollywood ; Noel G. McHale ; Keith D. Thornbury ; Gerard P. Sergeant ; ^{gerard.sergeant@dkit.ie" class="auth_mail" title="E-mail the corresponding author}
• 关键词：urinary bladder ; muscle contraction ; transient receptor potential channels ; acetylcholine ; cholinergic agents
• 刊名：The Journal of Urology
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：196
• 期：6
• 页码：1796-1808
• 全文大小：2519 K

文摘

Muscarinic receptor mediated contractions of the detrusor rely on Ca²⁺ influx through voltage-gated Ca²⁺ channels but to our knowledge the mechanism linking stimulation of M3Rs to the activation of voltage dependent Ca²⁺ channels has not been established. TRPC4 channels are receptor operated cation channels that couple muscarinic receptor activation to depolarization of intestinal smooth muscle cells, voltage-activated Ca²⁺ influx and contraction. We investigated whether TRPC4 channels are involved in cholinergic mediated contractions of the detrusor.

d="absSec_2">Materials and Methods

d="abspara0015">Isometric tension recordings were made on strips of murine detrusor and intracellular Ca²⁺ measurements were made on isolated detrusor myocytes using confocal microscopy. Transcriptional expression of TRPC and IP₃R subtypes in intact detrusor strips and isolated detrusor myocytes was assessed using reverse transcriptase-polymerase chain reaction.

d="absSec_3">Results

d="abspara0020">Cholinergic stimulation of the detrusor induced by electrical field stimulation or exogenous application of carbachol or neostigmine evoked contractions consisting of a transient plus a tonic response, which was blocked by ML204, an inhibitor of TRPC4 channels. A phasic oscillatory component was blocked by the IP₃R inhibitor 2-APB. Carbachol evoked reproducible Ca²⁺ responses in isolated detrusor myocytes, consisting of an initial Ca²⁺ transient followed by Ca²⁺ oscillations. ML204 inhibited the initial Ca²⁺ transient whereas 2-APB inhibited the Ca²⁺ oscillations. Reverse transcriptase-polymerase chain reaction experiments showed that TRPC4β, TRPC6 and IP₃R1 were selectively expressed in isolated detrusor myocytes. Control experiments demonstrated that ML204 did not affect L-type Ca²⁺ or BK current amplitude, caffeine induced Ca²⁺ transients or KCl induced contractions of the detrusor.

d="absSec_4">Conclusions

d="abspara0025">Muscarinic receptor mediated contractions of the detrusor involve the activation of TRPC4β channels.