Meeting Abstract

S6-1.1  Saturday, Jan. 5  Computation meets GnRH neurons: Dynamic current clamping SUTER, Kelly; University of Texas, San Antonio kelly.suter@utsa.edu

Gonadotropin releasing hormone (GnRH) neurons form in part, a central neural oscillator that controls sexual reproduction through intermittent release of the GnRH peptide. Activity of GnRH neurons and, by extension release of GnRH has been proposed to reflect a combination of intrinsic properties and synaptic input. To understand synaptic processing in GnRH neurons we combine traditional electrophysiology and computational methods. In particular, we used the dynamic current clamping approach to understand how GnRH neurons process input from glutamate and GABA, two key neurotransmitters in the neuroendocrine hypothalamus. Dynamic current clamping allows one to construct simulated synaptic inputs and apply them to living GnRH neurons in hypothalamic brain slices. Our studies using dynamic clamping have demonstrated that despite the small amplitude of glutamatergic currents, they can drive repetitive firing at frequencies which are consistent with neuropeptide release. Furthermore, application of simulated GABAergic synapses with a depolarized reversal potential have revealed two functional subpopulations of GnRH neurons: one population where GABA chronically depolarizes membrane potential (without inducing action potentials) and a second population where GABAergic excitation results in slow spiking which is largely dependent on endogenous L-type calcium conductances. Finally, when AMPA-type and GABA-type simulated inputs are applied together, action potentials occur when the AMPA-type conductance occurs during the descending phase of GABAergic excitation, but with a relatively wide temporal window. Our findings suggest that, due to this wide temporal window, GABAergic inputs with a depolarized reversal potential could function as a �sophisticated device� for modulating firing patterns and, as such, may be a liable component in the control of GnRH neuronal firing.