Distribution of the cells of primary afferent fibers to the cat auricle in relation to the innervated region.

The origin and peripheral distribution of the primary afferent fibers to the cat auricle were studied by the horseradish peroxidase (HRP) method. Following HRP injection into the whole region of the auricle, HRP-labeled cells were found ipsilaterally in the trigeminal ganglion, geniculate ganglion, superior ganglion of the vagus nerve and in the C1 to C4 spinal ganglia. In addition to the ganglia of cranial and spinal nerves, labeled cells were also observed in the facial nerve trunk and in the dorso-lateral portion of the superior cervical ganglion. In the case of HRP injection into the central region of the auricle, labeled cells were principally observed in the ganglia of cranial nerves and to a lesser degree in the spinal ganglia. On the contrary, in the case of HRP injection into the peripheral region of the auricle, labeled cells were principally observed in the spinal ganglia, although some were seen in the ganglia of cranial nerves. This study suggests that the cutaneous innervation of the auricle is supplied by both the cranial and spinal nerves, and that the central region of the auricle is strongly innervated by the cranial nerves and the peripheral region of the auricle is strongly innervated by the spinal nerves.