Intermedin inhibits norepinephrine-induced contraction of rat seminal vesicle

Objective: To study the effect of inter medin(IMD) on smooth muscle of rat seminal vesicles including the specific receptors and the signal pathways involved. Methods: The contraction of the seminal vesicle in response to norepinephrine (NE) and ADM2/IMD was studied by the organ bath method. The effects of antagonists for calcitonin gene related peptide (CGRP), adrenomedullin (ADM) and IMD receptors, and inhibitors of nitric oxide synthase, [L-NG-Nitroarginine Methyl Ester, L-NAME) and cAMP-dependent protein kinase (PKA), KT5720] were also investigated. The first overshoot, amplitude, frequency and basal tone were measured. Results: There is no significant effect of IMD on the initial overshoot, frequency and the basal tone in the seminal vesicle contraction. Only the amplitude of the contraction induced by NE was inhibited by IMD. The IMD inhibitory actions on amplitude were completely blocked by hADM22-52 and L-NAME, but not by hCGRP8-37 or KT5720. Furthermore, the action was diminished by IMD17-47. Conclusion: The results demonstrated that the inhibitory action of IMD on NE-induced seminal vesicle contraction was mediated via the ADM receptor(s) and the nitric oxide production pathway, partially by the IMD receptor, but not by the CGRP receptor and the cAMP-PKA pathway