Paul  Fuchs, Ph.D

John E. Bordley Professor of Otolaryngology- Head and Neck Surgery

Telephone Number:   (410) 955-6311

Fax Number:   (410) 614-4748

Johns Hopkins University

School of Medicine

Department of Otolaryngology, Head and Neck Surgery

Baltimore, MD 21205

Room: 818 Ross Bldg.

We use a combination of biophysical, molecular genetic and histological techniques to examine excitability and synaptic function in mechanosensory hair cells of the vertebrate cochlea. These sensory cells transduce mechanical inputs into receptor potentials whose waveform and amplitude encode the information content of sound. A specific complement of voltage and ligand-gated ion channels shape the receptor potential for each hair cell and determine the timing and efficacy of transmitter release. Presently we focus on two main topics.

1. The cholinergic inhibition of hair cells. Efferent neurons from the brainstem inhibit cochlear hair cells by the release of acetylcholine. We have identified two of the ion channels involved in the cholinergic response, an unusual nicotinic receptor, and a small conductance, calcium-activated potassium channel.  We collaborate with Dr. A.B. Elgoyhen of the University of Buenos Aires (who first cloned the hair cell’s acetylcholine receptor subunits) to study transgenic mouse models in which specific alterations have been made in these proteins.  An unresolved question concerns the role of intracellular calcium stores in augmenting cholinergic inhibition.  Our work on efferent synapses has recently expanded to include mechanisms of plasticity that modify the efficacy of inhibitory feedback. 

2.  Type II cochlear afferents.  These unmyelinated neurons make up a small minority of the afferent innervation of the cochlea, and till recently little was known of their function.  We’ve used patch-clamp recording in excised cochlear tissue to study these mysterious neurons.  Emerging evidence suggests that type II afferents would be activated only by damaging levels of sound.  Thus they may function analogously to C fibers that subserve pain and temperature sensation in the somatic nervous system.  If proven true this provides new insights into pathogenic mechanisms of peripheral disorders such as hyperacusis and tinnitus.