MOLECULAR AND FUNCTIONAL CHARACTERIZATION OF THE NICOTINIC CHOLINERGIC RECEPTOR AT THE EFFERENT SYNAPSE OF ZEBRAFISH LATERAL LINE

AGUSTIN CARPANETO FREIXAS; CAROLINA WEDEMEYER; PAOLA PLAZAS; ANA BELÉN ELGOYHEN

Congreso; Reunion Anual de la Sociedad Argentina de Neurociencias; 2017

Zebrafish (z) lateral line (LL) is a mechanosensory system that detects water movements and pressure changes. It consists of hair cells innervated by afferent neurons that transmit information to the CNS and by efferent neurons that contact directly to hair cells. LL hair cells share structural, functional and molecular characteristics with those in vertebrate inner ear. Efferent stimulation to the LL and the inner ear leads to similar effects suggesting the existence of similar synaptic mechanisms. It is known that the alpha9 alpha10 (a9 a10) nicotinic receptor (nAChR) mediates efferent transmission in the cochlea, however this information is lacking for zLL. Zebrafish has two a9 genes, located in chromosomes 1 (a9-1) and 14 (a9-14) and two a10 genes in chromosomes 15 (a10-15) and 21 (a10-21). To characterize the nAChRs at the efferent synapse in zLL, we have cloned all za9 and za10 subunits, expressed them in X. laevis oocytes and performed electrophysiological recordings under two-electrode voltage-clamp. Whereas ACh activates za9-1 homomeric nAChRs (EC50=11.71 uM), zα10-15 are only functional when co-expressed with zα9-1 (ACh EC50=437 uM). Moreover, zα9-1 nAChRs are blocked reversibly by strychnine with an IC50 of 0.12 uM. Both za9-1 and za9-1 za10-15 nAChRs exhibit high Ca2+ permeability and large desensitization rates. To study the properties of native nAChR at zLL, we are setting up procedures to perform whole cell patch clamp in zLL hair cells.