MOLECULAR CHARACTERIZATION OF MUSCARINIC RECEPTORS IN THE HUMAN VESTIBULAR PERIPHERY - IMPLICATIONS FOR PHARMACOTHERAPY

Hypothesis: Muscarinic acetylcholine receptor subtypes are expressed i n the human vestibular periphery to receive efferent innervation on th e type II vestibular hair cells and primary afferent dendrites. Backgr ound: Previous immunohistochemical and electrophysiologic studies have shown that acetylcholine (ACh) is likely the primary neurotransmitter of the efferent vestibular periphery. The structural distribution of nicotinic receptors (nAChR) and muscarinic receptors (mAChR) are not w ell established in the human vestibular periphery. Methods: Reverse tr anscription polymerase chain reaction (RT-PCR) was used to study the e xpression of all five mAChR subtypes in Scarpa's ganglia and the vesti bular end-organs of the rat and human. Results: The authors found mi t hrough m5 expression in rats. and mi, m2, and m5 expression in humans. Conclusions: These studies show evidence that both muscarinic acetylc holine receptors sire present in the human vestibular periphery in add ition to the nicotinic receptors reported previously. The pharmacologi c implications of these data are discussed.