[Multiple receptor interactions in the electrically stimulated ductus deferens of the guinea-pig]

The evidence that ATP is released with noradrenaline as a cotransmitter from sympathetic nerve endings in the isolated guinea-pig vas deferens, had led to investigate the potential interactive effects of P2 and alpha 1 receptors, extending the observations to potentially synergistic interactions of histamine-, acetylcholine- and serotonin-receptors. Ineffective concentrations of histamine, carbachol and serotonin increase the neurogenic response to field stimulation; this effect is prevented by the specific antagonist. The responses to the exogenously applied ATP and noradrenaline are increased as well, suggesting that this synergistic interaction of carbachol is less specific. It can be envisaged that receptor complex is a multicomponent system with subunits specific for the primary neurotransmitter and accessory subunits which may interact to increase the responsiveness of the target cell to simultaneous afferent stimuli.