Adenosine mediates a slow hyperpolarizing synaptic potential in autonomic neurones

Abstract

Considerable evidence has accumulated suggesting that purines, adenosine and ATP function as neurotransmitters in the central and peripheral nervous systems. Burnstock has proposed that purinergic receptors be classified into two types, P1 and P2, having adenosine and ATP, respectively, as agonist prototypes. Recent data suggest that ATP may mediate a synaptic potential in guinea pig vas deferens, but no such evidence exists for adenosine. The presence of a non-cholinergic, non-adrenergic nerve supply to the urinary bladder has been postulated and termed purinergic, as these nerves have been shown to release ATP. Furthermore, atropine-resistant contractions of bladder smooth muscle are thought to be mediated by ATP, while in situ experiments in vesical parasympathetic ganglia have suggested that a purinergic modulatory mechanism may control urinary bladder function. We now report the presence of a slow hyperpolarizing synaptic potential (slow-h.s.p.) in neurones of cat vesical parasympathetic ganglia, produced by stimulating the preganglionic nerves, and provide evidence that the slow-h.s.p. is mediated by adenosine.