抄録
Sensory nerves play a significant role in regulating spontaneous contractions of the renal pelvis, while autonomic motor nerves have a relatively small role. The major inhibitory neurotransmitter is calcitonin gene-related peptide (CGRP), but the cellular mechanisms of its action are not well understood. Changes in the intracellular Ca concentrations were recorded from fluo-4 loaded smooth muscle bundles of the mouse renal pelvis. Electrical and mechanical responses were recorded separately. The effects of stimulating capsaicin (CAP)-sensitive sensory nerves on spontaneous activity were compared with the effects of applying human CGRP (hCGRP).Renal pelvis preparations exhibited spontaneous action potentials, Ca transients and contractions. CAP (10 μM) caused a long-lasting inhibition of spontaneous activity which was often preceded by a transient excitation. Similarly, hCGRP (0.1 μM), isoproterenol (10 μM), forskolin (1 μM) and 8 Bromo-cAMP (1 mM) all suppressed spontaneous activity. These inhibitory effects were reduced in preparations previously treated with the ATP-sensitive K channel blocker, glybenclamide (10 μM). In mouse renal pelvis, stimulation of cyclic AMP production in smooth muscle may activate ATP-sensitive K channels to hyperpolarize the membrane and reduce the frequency of spontaneous activity. This pathway may be involved in sensory nerve-mediated regulation of spontaneous activity by releasing CGRP. [J Physiol Sci. 2008;58 Suppl:S55]
