CACNA1B and Alzheimer disease: Next, to determine the molecular mechanism for this apparent hyperexcitability in Ptchd1KD AD thalamic neurons, Roy et al. used FISH and elucidated that the expression of two transcripts, Cacna1a and Cacna1b, that encode for voltage-gated P-type calcium channel subunits alpha-1A (which contain the Ca2+ pore of Cav2.1 channels) and alpha-1B (Cav2.2 channels), respectively, were both markedly lower in these neurons.