Adjacent sections of membrane are pinched off to form new vesicles. Neuropeptides are synthesized in the perikaryon of the neuron, and must be transported to the nerve terminal before they can be released. D. Termination of the effect of the released neurotransmitter. At cholinoceptive sites, this occurs by metabolic inactivation by an exceedingly efficient enzyme, acetylcholinesterase. At adrenoceptive sites, the major mechanism is inactivation by reuptake of the neurotransmitter into the presynaptic nerve terminal, although some metabolic inactivation also occurs.
Diffusion also occurs to some extent in both cholinergic and adrenergic receptor sites.
Peptides are hydrolyzed by peptidases and dissipated by diffusion. Reuptake has as yet not been demonstrated. VI Mechanisms of action of drugs that influence the ANS A. Interference with synthesis of the transmitter 1. Cholinergic a. Hemicholinium causes blockade of choline uptake with consequent depletion of ACh. B. Metabolic transformation by the same pathway as the precursor of the neurotransmitter.