Observations on facial nociception in a monkey after destruction of the rostral part of the trigeminal sensory nuclear complex.

Facial sensibility was assessed in a cynomolgus monkey in whom the trigeminal main sensory nucleus and the rostral part of the trigeminal nucleus oralis on one side had been destroyed. The animal responded equally to noxious mechanical stimuli applied to the two sides of the face; no deficiency in nociception could be detected. This finding suggests that the synaptic connections made by nociceptor afferents from the face in rostral parts of the trigeminal sensory nuclear complex are not essential for facial nociception. These observations are also consistent with the opinion that, from a functional point of view, facial nociceptor afferents have their principal synaptic connections in the nucleus caudalis of the trigeminal spinal complex.