Regulation of Neuronal Function by Choline and 4OH-GTS-21 Through 7 Nicotinic Receptors

Uteshev, Vladimir V., Edwin M. Meyer, and Roger L. Papke. Regulation of neuronal function by choline and 4OH-GTS-21 through 7 nicotinic receptors. J Neurophysiol 89: 1797–1806, 2003. First published December 4, 2002; 10.1152/jn.00943.2002. A unique feature of 7 nicotinic acetylcholine receptor physiology is that, under normal physiological conditions, 7 receptors are constantly perfused with their natural selective agonist, choline. Studying neurons of hypothalamic tuberomammillary (TM) nucleus, we show that choline and the selective 7 receptor agonist 4OH-GTS-21 can regulate neuronal functions directly, via activation of the native 7 receptors, and indirectly, via desensitizing those receptors or transferring them into a state “primed” for desensitization. The direct action produces depolarization and thereby increases the TM neuron spontaneous firing (SF) rate. The regulation of the spontaneous firing rate is robust in a nonphysiological range of choline concentrations 200 M. However, modest effects persist at concentrations of choline that are likely to be attained perineuronally under some conditions (20–100 M). At high physiological concentration levels, the indirect choline action reduces or even eliminates the responsiveness of 7 receptors and their availability to other strong cholinergic inputs. Similarly to choline, 4OH-GTS-21 increases the TM neuron spontaneous firing rate via activation of 7 receptors, and this regulation is robust in the range of clinically relevant concentrations of 4OH-GTS-21. We conclude that factors that regulate choline accumulation in the brain and in experimental slices such as choline uptake, hydrolysis of ACh, membrane phosphatidylcholine catabolism, and solution perfusion rate influence 7 nAChR neuronal and synaptic functions, especially under pathological conditions such as stroke, seizures, Alzheimer’s disease, and head trauma, when the choline concentration in the CSF is expected to rise.