AUTHOR=Baumann Veronika , Lehnert Simon , Leibold Christian , Koch Ursula 

TITLE=Tonotopic organization of the hyperpolarization-activated current (Ih) in the mammalian medial superior olive

JOURNAL=Frontiers in Neural Circuits

VOLUME=7

YEAR=2013

URL=https://www.frontiersin.org/journals/neural-circuits/articles/10.3389/fncir.2013.00117

DOI=10.3389/fncir.2013.00117

ISSN=1662-5110

ABSTRACT=<p>Neuronal membrane properties can largely vary even within distinct morphological cell classes. The mechanisms and functional consequences of this diversity, however, are little explored. In the medial superior olive (MSO), a brainstem nucleus that performs binaural coincidence detection, membrane properties at rest are largely governed by the hyperpolarization-activated inward current (I<sub>h</sub>) which enables the temporally precise integration of excitatory and inhibitory inputs. Here, we report that I<sub>h</sub> density varies along the putative tonotopic axis of the MSO with I<sub>h</sub> being largest in ventral, high-frequency (HF) processing neurons. Also I<sub>h</sub> half-maximal activation voltage and time constant are differentially distributed such that I<sub>h</sub> of the putative HF processing neurons activate faster and at more depolarized levels. Intracellular application of saturating concentrations of cyclic AMP removed the regional difference in hyperpolarization-activated cyclic nucleotide gated (HCN) channel activation, but not I<sub>h</sub> density. Experimental data in conjunction with a computational model suggest that increased I<sub>h</sub> levels are helpful in counteracting temporal summation of phase-locked inhibitory inputs which is particularly prominent in HF neurons.</p>