THE POTASSIUM CHANNEL SUBUNIT KV3.1B IS LOCALIZED TO SOMATIC AND AXONAL MEMBRANES OF SPECIFIC POPULATIONS OF CNS NEURONS

Potassium channels play major roles in the regulation of many aspects of neuronal excitability. These channels are particularly well suited for such multiplicity of roles since there is a large diversity of cha nnel types. This diversity contributes to the ability of specific neur ons (and possibly different regions of the same neuron) to respond uni quely to a given input. Neuronal integration depends on the local resp onse of spatially segregated inputs to the cell and the communication of these integration centers with the axon. Therefore, the functional implications of a given set of K+ channels varies depending on their p recise location on the neuronal surface. Site-specific antibodies were utilized to characterize the distribution of KV3.1b, a subunit of vol tage-gated K+ channels in CNS neurons. KV3.1b subunits are expressed i n specific neuronal populations of the rat brain, such as cerebellar g ranule cells, projecting neurons of deep cerebellar nuclei, the substa ntia nigra pars-reticulata, the globus pallidus, and the ventral thala mus (reticular thalamic nucleus, ventral lateral geniculate and zona i ncerta). The KV3.1b protein is also present in various neuronal popula tions involved in the processing of auditory signals, including the in ferior colliculus, the nuclei of the lateral lemniscus, the superior o live, and some parts of the cochlear nuclei; as well as in several oth er neuronal groups in the brainstem (e.g., in the oculomotor nucleus, the pontine nuclei, the reticulotegmental nucleus of the pens, trigemi nal and vestibular nuclei, and the reticular formation) and subsets of neurons in the neocortex, the hippocampus and the caudate-putamen sho wn by double staining to correspond to neurons containing parvalbumin. KV3.1b subunits are localized predominantly in somatic and axonal mem branes (particularly in axonal terminal fields) but are much less prom inent in dendritic arborizations. This distribution is different than that of other subunits of voltage gated K+ channels and is consistent with a role in the modulation of action potentials. KV3.1b proteins ha ve a cellular and subcellular distribution different than the related KV3.2 subunits which express in Xenopus oocytes currents similar to th ose expressed by KV3.1b.