Electrophysiological and biochemical responses of mouse vomeronasal receptor cells to urine-derived compounds: possible mechanism of action

Receptor cells of the vomeronasal organ (VNO) are thought to detectpheromone-like molecules important for reproductive physiology. Severalcompounds derived from male mouse urine have been demonstrated to affectendocrine events in female mice. In the present study, the ability of thesecompounds to affect VNO activity was tested. In dissociated VNO cells heldunder voltage clamp conditions, application of dehydro-exo-brevicomin (DHB)evoked an outward current at negative holding potentials and an inwardcurrent at positive holding potentials. Under current clamp, DHB reducedaction potential firing. Since DHB application caused a decrease inmembrane conductance, this compound appeared to act by reducing inwardcurrent through closing an ion channel. Biochemical experiments tested theeffects of DHB and 2- (sec-butyl)-4,5-dihydrothiazole (SBT) on cAMP levelsin the VNO. A mixture of DHB and SBT decreased cAMP levels in VNO sensorytissue and had no effect on VNO non-sensory tissue. The results suggestthat pheromones have an inhibitory influence on action potential generationand on cAMP levels in receptor cells of the VNO.