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^1–4. Burnstock² 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 deferons^5,6, but no such evidence exists for adenosine. The presence of a non-cholinergic, non-adrenergic nerve supply to the urinary bladder has been postulated^7,8 and termed purinergic^1,2, as these nerves have been shown to release ATP⁷. Furthermore, atropine-resistant contractions of bladder smooth muscle are thought to be mediated by ATP, while in situ experiments^9,10 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.