Although nicotinic acetylcholine receptors (nAChRs) have been studied extensively in many areas of the mammalian nervous system, they have been virtually overlooked in the cerebellum up to this point. Previous studies in rodent, monkey, and human cerebellum have detected mRNA transcripts for at least eight different nAChR subunits, including α2, α4, α5, α6, α7, β2, β3, and β4, (Didier et al., 1995; Quik et al. 2000); but practically no studies has been directed at determining which specific nAChR subtypes are actually present in the cerebellum and very little is known about their functional implications. Therefore, the objectives of my thesis research were to quantitatively determine the major heteromeric nAChR subtypes in the cerebellum, determine their distribution within the cerebellum, and to begin to determine the potential functional roles they play there. My specific aims were: (1) To fully determine the heteromeric nAChR subtypes (as defined by subunit composition) in the cerebellum. (2) To determine the location of these receptors in the circuitry of the cerebellum, including their location on extrinsic axons that innervate the cerebellum or on intrinsic cell types of the cerebellum. (3) To determine potential roles of nAChRs in the cerebellum: developmentally, physiologically, and upon chronic nicotine administration.
In carrying out these studies, I used several methods including: radioligand binding assays, RNAse protection assays, immunoprecipitation and sequential immunoprecipitation of radiolabeled receptors with subunit-specific antibodies, various lesion models, immunohistochemistry, assays of glutamate release, and electrophysiology in both granule cell cultures and cerebellar slices. Using these techniques, I delineated what subtypes are present in the cerebellum, where they are distributed, and what they may be doing. I believe that this research has resulted in better understanding of the potential role(s) of nAChRs in the cerebellum and their possible clinical implications in diseases such as autism and cerebellar ataxias.
My Research