The p-type calcium channel is a type of voltage-dependent calcium channel

Voltage-dependent calcium channel

Voltage-dependent calcium channels are a group of voltage-gated ion channels found in excitable cells with a permeability to the ion Ca2+...

. Like the others of this class, the α1 subunit is the one that determines most of the channel's properties.

P-type ('P' for cerebellar Purkinje cells) calcium channels play a similar role to the N-type calcium channel

N-type calcium channel

The N-type calcium channel is a type of voltage-dependent calcium channel. Like the others of this class, the α1 subunit forms the pore through which calcium enters the cell and determines most of the channel's properties...

 in neurotransmitter release at the presynaptic terminal, and in neuronal integration in many neuronal types.

They are also found in Purkinje fibers

Purkinje fibers

For the nervous cells, see Purkinje cellPurkinje fibers are located in the inner ventricular walls of the heart, just beneath the endocardium...

in the electrical conduction system of the heart

Electrical conduction system of the heart

The normal intrinsic electrical conduction of the heart allows electrical propagation to be transmitted from the Sinoatrial Node through both atria and forward to the Atrioventricular Node. Normal/baseline physiology allows further propagation from the AV node to the ventricle or Purkinje Fibers...

. Their properties are less well understood.

P channels were discovered in cerebellar Purkinje cells by Llinas and Sugimori and named P channels by Llinas et al.