Properties of IA in a neuron of the dorsal raphe nucleus

Voltage clamp data were analyzed in order to characterize the properties of the fast potassium transient current IAIA for a presumed serotonergic neuron of the rat dorsal raphe nucleus (DRN). We obtain maximal conductance, time constants of activation and inactivation, and the steady state activation and inactivation functions m∞ and h∞, as Boltzmann curves, defined by half-activation potentials and slope factors.IAIA is estimated as g¯(V−Vrev)m4h, with g¯=20.5 nS. For activation, the half-activation potential is Va = − 52.5 mV with slope factor ka = 16.5 mV, whereas for inactivation the corresponding quantities are − 91.5 mV and − 9.3 mV. We discuss the results in terms of the corresponding properties of IAIA in other cell types and their possible relevance to pacemaking activity in cells of the DRN. Methods of identification of serotonergic DRN neurons and the nature of the Kv channels underlying the A-type current are also discussed.

Research Highlights► First report of IA in dorsal raphe neurons. ► Novel and accurate method of finding activation functions. ► Excellent agreement with experiment.