Neuronal nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that are necessary in memory and cognition. They are pentameric and consist of Î± and Î² subunits. They are most commonly heteromeric but, can sometimes be homomeric. nAChRs are activated by many ligands including nicotine (exogenous) and acetylcholine (endogenous).nAChRs are located on hippocampal interneurons. The interneurons, although sparse, control the synchronous firing of the pyramidal cells. However, the hippocampal interneuron structure and function is quite diverse and not fully characterized. Therefore, we sought to quantify nAChR subunit mRNA levels using real-time PCR of CA1 hippocampal interneurons.Surprisingly we found that the Î±3 and Î²2 mRNA subunits were the highest expressed and highest co-expressed subunits. Additionally, the Î±4 mRNA subunit was the lowest expressed of the subunits detected. The Î±4 subunit is one of the most pharmacologically targeted nAChR subunits and is found throughout the rest of the brain at much higher levels than the Î±3 mRNA subunit. Upon PCR analysis two subpopulations of the Î±3 and Î²2 subunits emerged: those that contained 3X more Î±3 than Î²2 and those that contained 3X more Î²2 than Î±3. Therefore, we hypothesized that two likely Î±3Î²2 nAChR stoichiometries are present in hippocampal interneurons. We differentiated their kinetic properties using electrophysiology.Additionally, like the Î±4 subunit, the Î±7 subunit is highly targeted in cognitive therapeutics. Since, the Î±7 subunit is the most characterized nAChR subunit, there are current efforts to develop allosteric modulators of the Î±7 subunit. The Î±7 subunit is found at moderate levels within hippocampal interneurons and remains a valid target. Current treatment options for Alzheimer's disease, and other dementias are limited and only mildly effective. Therefore, we sought to characterize the effect of 3-furan-2-yl-N-p-tolyl-acrylamide (PAM-2) on Î±7.Furthermore, there are no current methods to distinguish the Î±7 from the Î±7Î²2 nAChRs during whole cell electrophysiological recordings. Therefore, we also characterized the PAM-2 effect on Î±7Î²2 nAChRs. Our results highlight at least 2 ways PAM-2 can be used to differentiate Î±7 from the Î±7Î²2 during whole-cell recordings.
College and Department
Life Sciences; Physiology and Developmental Biology
BYU ScholarsArchive Citation
Jackson, Doris Clark, "Characterization of Neuronal Nicotinic Acetylcholine Receptors and their Positive Allosteric Modulators" (2017). Theses and Dissertations. 6856.
nicotinic acetylcholine receptors (nAChRs), hippocampus, interneurons, electrophysiology, allosteric modulators, real-time PCR