Journal of Neuroscience, Vol 8, 1971-1980, Copyright © 1988 by Society for Neuroscience
Developmental changes in K+-selective channel activity during differentiation of the Purkinje neuron in culture
AJ Yool, VE Dionne and DL Gruol
Division of Preclinical Neuroscience and Endocrinology, Research Institute of Scripps Clinic, La Jolla, California 92037.
The cerebellar Purkinje neuron cultured from 20 d rat embryos is
electrically inexcitable when immature, and acquires excitable membrane
properties according to a programmed developmental sequence, thus providing
a useful model for investigating mechanisms of CNS neuronal development.
Using conventional patch-clamp techniques, we have characterized the the
predominant classes of active K+-selective channels at a range of ages
encompassing the entire developmental process from 5 to 29 d in vitro
(DIV), and have shown pharmacologically that these channels are important
contributors to the patterns of spontaneous activity generated by the
Purkinje neurons. The 4 predominant classes of K+ channels that are active
during steady-state depolarizing voltage commands are identified by unit
conductances as the 27, 44, 70, and 100 pS channels, and show differences
in several properties, including voltage dependence, sensitivity to
tetraethylammonium chloride (TEA), mean open time, and time of appearance
during development. Intracellular current-clamp recordings show that
physiological maturation of the Purkinje neuron entails increases in the
firing rate, the diversity of spike events that comprise spontaneous
activity, and the sensitivity of spontaneous activity to disruption by the
K+ channel blocker TEA. This increase in sensitivity to TEA correlates with
the new expression of activity of the larger-conductance TEA-sensitive
classes of K+ channel (70 and 100 pS types). These data show that
developmental regulation of the activity of K+-selective channels
contributes significantly to the ionic mechanisms that underlie the
developmental transitions in spontaneous activity patterns in the Purkinje
neuron.