Pain Conduction in the Phrenic Nerve

Summary. The application of noxious stimuli to the diaphragm (pinching, heat above 40° C, hypertonic NaCl‐solutions and acetic acid) produces in the phrenic nerve of the cat δ‐potentials whilst in the dog both δ‐ and C‐potentials appear. Each inspiration produces a volley of rapidly conducted impulses in the phrenic nerve. These impulses are obviously produced by α‐ and β‐fibres. Large spikes are not produced by a noxious stimulus such as acetic acid applied on the abdominal surface of the diaphragm. It is thus concluded that pain is transmitted in the phrenic nerve of the animals investigated by δ‐ and C‐ fibres only. Pacinian corpuscles have not been observed in the pericardium or in the pleura of the cat or the dog. The action potential records from the peripheral end of the phrenic nerve have not revealed the appearance of any spikes which could be regarded as arising from such corpuscles.