Properties of mechanoreceptor afferent fibres in left inferior cardiac nerve.

Single afferent fibres with receptive field in the heart chambers and great vessels were dissected from the thoracic sympathetic chain. The fibres were identified by the electrical stimulation of the left inferior cardiac nerve, which was left in continuity with the heart. Fifty-six percent of the afferent fibres from the left inferior cardiac nerve were spontaneously active, the rest was silent. The spontaneously active fibres with receptive field in the aorta or left ventricle fired in close relation to the cardiac cycle as revealed by constructing post-R-wave time histogram of their activity. Fibres with cardiac rhythmicity were all myelinated. The second group of the spontaneously active fibres had their receptive field in the left atrium. The activity of these fibres was slightly or not at all correlated with cardiac cycle. They were both myelinated fibres.