Voltage-gated sodium channels are present on both the neural and capsular structures of Pacinian corpuscles

It has long been accepted that action potentials arising from Pacinian corpuscles (PCs) originate at the first node of Ranvier located within the PC and that the mechanotransduction events (receptor potentials) are formed by stretch-activated channels selectively sensitive predominantly to Na+. Also, it has been shown previously that tetrodotoxin (TTX) affects the receptor potential suggesting that transduction may involve voltage-sensitive Na+ channels. To determine whether voltage-sensitive Na+ channels exist in the membrane thought to be responsible for transduction, immunocytochemical studies were performed using polyclonal antibodies raised in rabbit against the alpha subunit of rat type I and type II voltage-gated sodium channels. The results show the presence of label on the neurite and axolemma, as well as in the node regions. Interestingly, labeling is also found on the inner and outer lamellae that form the non-neural accessory structure surrounding the neurite. The presence of this label in the surrounding lamellae suggests that voltage-sensitive Na+ channels, that are involved in both transduction and action-potential generation, may be made available to the neurite via transport from the lamellae, a mechanism perhaps operating in parallel to axoplasmic transport.