Distribution of the messenger RNA for the small conductance calcium-activated potassium channel SK3 in the adult rat brain and correlation with immunoreactivity

Small conductance calcium-activated potassium channels are voltage independ ent potassium channels which modulate the firing patterns of neurons by act ivating the slow component of the afterhyperpolarization. The genes encodin g a family of small conductance calcium-activated potassium channels have b een cloned and up to now three known members have been described and named small conductance calcium-activated potassium channel type 1, small conduct ance calcium-activated potassium channel type 2 and small conductance calci um-activated potassium channel type 3; the distribution of their messenger RNA in the rat CNS has already been performed but only in a limited detail. The present study represents the first detailed analysis of small conductan ce calcium-activated potassium channel type 3 mRNA distribution in the adul t rat brain and resulted in a strong to moderate expression of signal in me dial habenular nucleus, substantia nigra compact part, suprachiasmatic nucl eus, ventral tegmental area, lateral septum, dorsal raphe and locus coerule us. Immunohistological experiments were also performed and confirmed the pr esence of small conductance calcium-activated potassium channel type 3 prot ein in medial habenular nucleus, locus coeruleus and dorsal raphe. Given the importance of dorsal raphe, locus coeruleus and substantia nigra/ ventral tegmental area for serotonergic, noradrenergic and dopaminergic tra nsmission respectively, our results pose the morphological basis for furthe r studies on the action of small conductance calcium-activated potassium ch annel type 3 in serotonergic, noradrenergic and dopaminergic transmission. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.