Ca2+-activated potassium currents (IK(Ca)) are an important link between the intracellular signaling system and the membrane potential, which shape intrinsic electrophysiological properties. To better understand the ionic mechanisms that mediate intrinsic firing properties of olfactory uniglomerular projection neurons (uPN), we used whole-cell patch clamp recordings in an intact, adult brain preparation of the male cockroach Periplaneta americana to analyze IK(Ca). In the insect brain uPNs form the principal pathway from the antennal lobe to the protocerebrum, where centers for multimodal sensory processing and learning are located. In uPNs the activation of IK(Ca) was clearly voltage and Ca2+ dependent. Thus, under physiological conditions IK(Ca) is strongly dependent on the Ca2+ influx kinetics and on the membrane potential. The biophysical characterization suggest that IK(Ca) is generated by BK channels. An SK channel generated current could not be detected. IK(Ca) was sensitive to charybdotoxin and iberiotoxin but not to apamin. The functional role of IK(Ca) was analyzed in occlusion experiments under current clamp, in which portions of IK(Ca) were blocked by charybdotoxin or iberiotoxin. Blockade of IK(Ca) showed that IK(Ca) contributes significantly to the intrinsic electrophysiological properties such as the action potential waveform and membrane excitability.
- antennal lobe
- calcium activated potassium current
- Periplaneta americana
- Copyright © 2015, Journal of Neurophysiology