DISTRIBUTION OF THE VOLTAGE-DEPENDENT CALCIUM-CHANNEL ALPHA(1A) SUBUNIT THROUGHOUT THE MATURE RAT-BRAIN AND ITS RELATIONSHIP TO NEUROTRANSMITTER PATHWAYS

The alpha(1) subunit provides both the voltage-sensing mechanism and t he ion pore of voltage-dependent calcium channels. Of the six classes of alpha(1) subunit cloned to date, alpha(1) is the subject of debate in terms of its functional correlate, although it is generally thought to encode voltage-dependent calcium channels of the omega-agatoxin IV A-sensitive, P/Q type. In the present study, an alpha(1A)-specific rib oprobe and antibody were used with in situ hybridisation and immunohis tochemical techniques to :localise alpha(1A) messenger ribonucleic aci d transcripts and subunit protein throughout the mature rat brain. Dua l localisation of alpha(1A) protein and markers for acetylcholine, cat echolamines, and 5-hydroxytryptamine have also been performed in a num ber of discrete areas. Abundant and widespread distribution of alpha(1 A) protein was found, with immunoreactivity occurring both in cell bod ies and as punctate staining in areas of neuronal processes. Several a ssociations were noted across alpha(1A) localisation, defined neuroana tomical regions, and neurotransmitter systems. However, alpha(1A) expr ession was not confined to loci corresponding to any one neurotransmit ter type, although a high level of expression was observed in choliner gic neurones. The distribution of the alpha(1A) subunit in the rat cor responded well with the limited human mapping data that are available. J. Comp. Neurol. 397:251-267, 1998. (C) 1998 Wiley-Liss, Inc.