J. Fernando Garcia-Diaz

Research in this lab centers on the regulation of ion channel expression during neuronal differentiation and on the modulation of ion channel activity by certain neurotransmitters. We use cell culture techniques, electrophysiology and fluorescence microscopy to analyze the expression pattern and regulation of ion channels in cochlear ganglion (CG) neurons during development. Spiral or cochlear ganglion neurons are responsible for the faithful transmission of sound information from the hair cells in the organ of Corti (the sound transducing elements) to the cochlear nucleus in the brain and, thus, are endowed with a set of fast activating voltage-gated ion channels. We have analyzed the temporal pattern of expression of voltage-gated sodium, calcium and potassium channels in chick embryo CG neurons and found functionally relevant correlations between the development of membrane currents and the innervation pattern of the cochlea (Garcia-Diaz et al., 1998; Garcia-Diaz, 1999). We are also investigating whether certain members of the nerve growth factor family of proteins (neurotrophins), released by the target cells of neurons, regulate the expression of ion channels during embryonic development (Jimenez et al., 1997; Garcia-Diaz, 1999). On the other hand, efferent innervation acting through muscarinic and purinergic receptors modulates the firing response of CG neurons to sound information. We are presently investigating whether the activation of these receptors, and the ensuing signaling events, modulate a cloned non-inactivating potassium channel transfected in a heterologous system.