NEUROGENIC CONTROL OF THE OVINE GALLBLADDER - ULTRASTRUCTURAL AND FUNCTIONAL-STUDY

The purpose of this study was to investigate the ultrastructure of the local nerve supply of ovine gallbladders as well as the functional ch aracteristics of inhibitory nerves. We used electron microscopy of thi n sections of ovine gallbladders and in vitro isometric tension record ing using gallbladder strips. Specifically, we measured contractile an d inhibitory responses induced by transmural electrical field stimulat ion (EFS). We found a ganglionated plexus with intramural nerve cells and interconnecting axons. Clear and large dense-core vesicles colocal ized in axons close to smooth muscle cells. EFS elicited gallbladder c ontractions which were converted to relaxation after atropine. EFS-ind uced relaxation was reduced by the nitric oxide (NO) synthase inhibito r, L-NOARG and blocked by propranolol and/or tetrodotoxin. In conclusi on, enteric ganglia and neurones with synaptic vesicles (clear and den se core) were detected close to smooth muscle bundles. Neural inhibiti on of gallbladder contraction was mediated by P-adrenoceptors coupled to NO generation.