Distribution of the voltage‐dependent calcium channel α1A subunit throughout the mature rat brain and its relationship to neurotransmitter pathways

The α1 subunit provides both the voltage‐sensing mechanism and the ion pore of voltage‐dependent calcium channels. Of the six classes of α1 subunit cloned to date, α1A is the subject of debate in terms of its functional correlate, although it is generally thought to encode voltage‐dependent calcium channels of the ω‐agatoxin IVA‐sensitive, P/Q type. In the present study, an α1A‐specific riboprobe and antibody were used with in situ hybridisation and immunohistochemical techniques to localise α1A messenger ribonucleic acid transcripts and subunit protein throughout the mature rat brain. Dual localisation of α1A protein and markers for acetylcholine, catecholamines, and 5‐hydroxytryptamine have also been performed in a number of discrete areas. Abundant and widespread distribution of α1A protein was found, with immunoreactivity occurring both in cell bodies and as punctate staining in areas of neuronal processes. Several associations were noted across α1A localisation, defined neuroanatomical regions, and neurotransmitter systems. However, α1A expression was not confined to loci corresponding to any one neurotransmitter type, although a high level of expression was observed in cholinergic neurones. The distribution of the α1A subunit in the rat corresponded well with the limited human mapping data that are available. J. Comp. Neurol. 397:251–267, 1998. © 1998 Wiley‐Liss, Inc.