ARE THERE NICOTINIC ACETYLCHOLINE RECEPTORS ON PHRENIC MOTOR NEURONS?

Abstract

Nicotinic acetylcholine receptors (nAChRs) are expressed throughout the central nervous system, including on neuron populations that control breathing. The specific locations of nAChRs on respiratory related neurons are relatively unknown and their presence on phrenic motor neurons (PMNs) could indicate a point at which developmental nicotine exposure may impact breathing. We hypothesize that application of nicotine to the PMNs will elicit changes in amplitude and area of respiratory motor bursting recorded from cervical 3-5 ventral roots due to the presence of nAChRs on PMNs. A brainstem spinal cord split-bath preparation was used to separately perfuse brainstem and spinal cord chambers with artificial cerebrospinal fluid (aCSF), and nicotinic aCSF was added to the spinal cord chamber. Burst amplitude and area under the curve were measured at baseline and during application of three different nicotine concentrations (400nM, 4M, 40M). Our results show that while 400nM nicotinic aCSF did not significantly affect the amplitude or area of bursts, both 4M and 40  nicotinic aCSF caused an initial increase in amplitude and area of the bursts, indicating nAChR activation, followed by a decrease in these parameters, indicating nAChR desensitization. These findings indicate the presence of nAChR on PMNs or neurons that synapse with PMNs.