Axoplasmic transport of muscarinic receptors

Abstract

The reality of axoplasmic transport is widely accepted; various neurotransmitters^1–3, enzymes^2–4, labelled proteins⁵ and peptides⁶ are known to move rapidly along the axons of different nerve fibres. In the terminals of sympathetic nerves, nor adrenaline release is controlled by various regulatory mechanisms which imply the occurrence of presynaptic receptors⁷. In this regard, there is considerable indirect physiological evidence for the existence of muscarinic cholinergic receptors in the sympathetic nerve endings^7–9; the stimulation by acetylcholine of such presynaptic receptors elicits an inhibitory effect on noradrenaline release^8,9. We now provide direct biochemical evidence for the occurrence in dog splenic nerve of muscarinic receptors which seem to move along the axon as suggested by their rapid accumulation on either side of a ligature.