Here we analyzed transient voltage-activated K+ currents (IA) of projection neurons and local interneurons in the antennal lobe (AL) of the cockroach Periplaneta americana. The AL is the first synaptic processing station for olfactory information in insects. Local interneurons are crucial for computing olfactory information and form local synaptic connections exclusively in the AL, while a primary task of the projection neurons is the transfer of preprocessed olfactory information from the AL to the protocerebrum. The different physiological tasks of these neurons require specialized physiological and morphological neuronal phenotypes. Here we asked if and how the different physiological phenotypes are reflected in the functional properties of IA, which is crucial for shaping intrinsic electrophysiological properties of neurons. Whole cell patch-clamp recordings from adult male P. americana showed that all their central AL neurons can generate IA. The current exhibited marked cell type specific differences in voltage dependence of steady-state activation and inactivation, and differences in inactivation kinetics during sustained depolarization. Pharmacological experiments revealed that IA in all neuron types was partially blocked by α-dendrotoxin and phrixotoxin-2, which are considered blockers with specificity for shaker- and shal-type channels, respectively. These findings suggest that IA in each cell type is a mixed current generated by channels of both families. The functional role of IA was analyzed in experiments under current-clamp, in which portions of IA were blocked by α-dendrotoxin or phrixotoxin-2. These experiments showed that IA contributes significantly to the intrinsic electrophysiological properties such as the action potential waveform and membrane excitability.
- local interneuron
- projection neuron
- Periplaneta americana
- Copyright © 2016, Journal of Neurophysiology