Movement of K⁺ across the Blood-Brain Barrier of the American Cockroach, Periplaneta americana

Abstract

<p>Several previous studies of the blood brain barrier (BBB) of the American cockroach, <em>Periplaneta americana</em>, have shown that it is involved in the regulation of K⁺ and Na⁺ flux across the ventral nerve cord (VNC). Na⁺ flux is regulated in part by a Na⁺/K⁺-ATPase but few mechanisms involved in the regulation of K⁺ flux have been identified. Using the scanning ion-selective electrode technique (SIET) K⁺ flux across the VNC can be measured. This technique was used to determine whether K⁺ flux is actively regulated and whether the BBB is involved in the regulation of K⁺ flux. An uptake of K⁺ is seen at the connectives and an efflux is seen at the ganglion under some conditions indicating cycling of K⁺ from the ganglion to the connective may be occurring. A Na⁺/K⁺-ATPase appears to contribute to an influx of K⁺ at the ganglion but not the connective. It is postulated that a K⁺/H⁺-exchanger is involved in maintaining K⁺levels at the ganglion. The presence of K⁺-channels (possibly Ca²⁺-gated) was detected at both the ganglion and the connective, although it appears that K⁺-channels play a greater role in regulating K⁺ flux at the connective. These results provide insights into the basic mechanisms regulating ion flux across the cockroach VNC.</p>