All L-type calcium channels are encoded by one of the Ca_V1 channel genes. These channels play a major role as a Ca²⁺ entry pathway in skeletal cardiac and smooth muscles as well as in neurons, endocrine cells and possibly in non-excitable cells such as hematopoetic and epithelial cells. All Ca_V1 channels are influenced by dihydropyridines (DHP) and are also referred to as DHP receptors. While the Ca_V1.1 and Ca_V1.4 isoforms are expressed in restricted tissues (skeletal muscle and retina, respectively), the expression of Ca_V1.2 is ubiquitous.^1,2

The Ca_V1.3 channels are also expressed, as are other L-type channels, in neurons and neuroendocrine cells. However, accumulated data has shown the expression of Ca_V1.3 in heart and suggests that it plays a major role in the generation of cardiac pacemaker activity.^3,4

Several peptidyl toxins have been described that are specific L-type channel blockers. These include the Mamba toxins Calcicludine (#SPC-650), Calciseptine (#C-500) and FS-2 (#F-700). So far no selective blocker for one of the Ca_V1 isoforms has been described.