THE RELEASE OF LABELLED ACETYLCHOLINE AND CHOLINE FROM CEREBRAL CORTICAL SLICES STIMULATED ELECTRICALLY

• Published in: British journal of pharmacology 1974-12, Vol.52 (4), p.499-507
• Main Authors: RICHARDSON, I.W., SZERB, J.C.
• Format: Article
• Language: English
• Subjects: Acetylcholine - metabolism; Animals; Atropine - pharmacology; Cerebral Cortex - metabolism; Cerebral Cortex - physiology; Choline - metabolism; Cholinesterase Inhibitors - pharmacology; Electric Stimulation; In Vitro Techniques; Physostigmine - pharmacology; Rats; Systematic Pharmacology; Time Factors
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.1974.tb09717.x

1 In order to establish the origin of the increased efflux of radioactivity caused by electrical stimulation of cerebral cortical slices which had been incubated with [3H]‐choline, labelled choline and acetylcholine (ACh) collected by superfusion were separated by gold precipitation. 2 In the presence of physostigmine electrical stimulation (1 Hz, 10 min) increased the release of only [3H]‐ACh which was greatly enhanced by the addition of atropine. 3 Continuous stimulation in the presence of physostigmine resulted in an evoked release of [3H]‐ACh which declined asymptotically. This evoked release appeared to follow first‐order kinetics with a rate constant which remained stable over the course of prolonged stimulation. 4 The rate constant for the evoked release of [3H]‐ACh with 1 Hz stimulation was three times greater in the presence of physostigmine and atropine than in the presence of physostigmine alone, while the size of the store from which [3H]‐ACh was released was nearly identical under these two conditions. 5 In the absence of physostigmine and atropine, stimulation caused the appearance of only [3H]‐choline in the samples. 6 Reduction of [3H]‐ACh stores before the application of physostigmine resulted in a reduced evoked release of total radioactivity, both in the absence or presence of physostigmine and atropine, and decreased the evoked release of [3H]‐ACh without affecting the release of [3H]‐choline. 7 Results suggest that electrical stimulation of cortical slices which had been incubated with [3H]‐choline causes the release of only [3H]‐ACh, both in the presence or absence of an anticholinesterase. The evoked increase in the efflux of total radioactivity is therefore a good measure of the release of [3H]‐ACh.