The carboxyl-terminus of Cav2.1 P/Q-type calcium channel plays an important role in Ca2+-dependent facilitation and inactivation (Lee et al, Nature 399:155; DeMaria et al, Nature 411:484). The EF hand lies within this region and is encoded by exons 36 and 37. In Cav2.1 calcium channels, exon 37 exhibits mutually exclusive splice variation, giving rise to either exon 37a or 37b. Facilitation is observed when exon 37a is expressed but not exon 37b (Chaudhuri et al, SFN abstract, 2001). We report here the relative distribution of the two splice forms across different regions of the human brain. Eight human cDNA libraries were analyzed: fetal whole brain, adult whole brain, amygdala, cerebellum, cerebral cortex, hippocampus, substantia nigra and thalamus. For each library, the PCR amplicons spanning exons 35 to 38 were cloned and more than 200 bacterial colonies were screened using exon 36 and exon 37a- or 37b-specific primers. The results indicated that exon 37a is predominantly expressed in the substantia ni...