POTASSIUM CURRENTS IN MOTONEURONS

The measurements of intrinsic unitary and macroscopic properties of po tassium channels in motoneurones constitutes an important step in the characterization of cellular function. A number of potassium currents contribute to the integrated function of motoneurones and this review considers the properties of the inward rectifier (I-h-type), calcium-d ependent (BK- and SK-types), delayed rectifier, transient outward, and leak currents. The modification of channel properties by agents such as serotonin and thyrotropin-releasing hormone is likely relevant to m odulation of motoneurone function. Indeed, even during the course of n ormal cell development, the expression and properties of particular po tassium channels can undergo considerable changes, which would be mani fested as altered firing patterns and excitability of motoneurones. Br ainstem and spinal cord slices have considerable utility for electroph ysiological studies and have been used in recordings from spinal, hypo glossal and facial motoneurones. New procedures have also been develop ed which would enhance the purification of cultured motoneurones for p atch-clamp experiments.