An increase in putative voltage dependent calcium channel number following reserpine treatment

Rats were treated with reserpine (0.2 mg/kg) on days 1, 3, and 5. On day 6, binding parameters for alpha-1 adrenergic receptors (3H-prazosin) and putative voltage dependent calcium channels, VDCC (3H-nitrendipine), were determined. There was an increase in both the number (2.1 fold) and affinity (1.8 fold) of alpha-1 adrenergic receptors following reserpine treatment. In addition, there was a 2.7 fold increase in the number of VDCCs, but no change in VDCC binding affinity, following reserpine treatment. These data are consistant with the development of smooth muscle supersensitivity following reserpine treatment in a variety of tissues, and suggest that VDCC number may be modulated by the cell in response to tonic levels of catecholamines. Changes in the number of VDCCs may be an important regulatory mechanism for cell function in physiologic and pathologic states.