ABSTRACT
Many neuropeptides, like angiotensins and vasopressin, are involved in the regulation of urinary bladder contractile activity. They activate the inositol-triphosphate signal pathway and increase intracellular calcium concentration. To determine the effect of ghrelin and extracellular calcium on the amplitude and force of angiotensin and vasopressin-mediated contractions of detrusor, we used strips from urinary bladder of Wistar rats. The obtained preparations were stimulated with Angiotensin II (Ang II) and arginine-vasopressin (AVP), independently and in combination with CaCl(2) or ghrelin. The simultaneous application of peptide and CaCl(2) increased the amplitude and the integral force (AUC) of muscle contraction for both neuropeptides. If ghrelin was applied to the preparation 30min prior to application of Ang II, it prevented the development of typical Ang II-mediated contraction. Ghrelin did not affect the amplitude of AVP-mediated contraction, but significantly lowered its integral force. Our experimental data indicate that the increase of calcium in the extracellular fluid possesses a synergistic effect on the neuropeptide-mediated contraction. The effects of ghrelin on Ang II- and AVP-mediated contractions allow us to express the assumption that the urinary bladder cells probably have ghrelin receptors which do not activate phospholipase C signal pathway.