Trigeminal primary afferent projections to the peribrachial area in the guinea pig

Transganglionic transport of horseradish peroxidase (HRP) was used to investigate trigeminal primary afferent endings in the peribrachial area of the guinea pig. After HRP application to several nerve branches of the three divisions of the trigeminal nerve, a projection to the caudal region of the ipsilateral peribrachial region was found for the infratrochlear, ethmoidal, supraorbital, zygomatic, zygomaticofacial, zygomaticotemporal and infraorbital-superior alveolar nerves. Random and scarce endings were also observed for the mental, inferior alveolar, buccal and mylohyoid nerves. No trigeminal primary projection to the peribrachial area was detected when HRP was applied to the sphenopalatine, lingual and auriculotemporal nerves. With the exception of the ethmoidal endings described in the muskrat, a primary afferent projection to the peribrachial region from the other trigeminal nerves has not hitherto been reported in mammals.