A qualitative investigation of the topographical representation of masticatory muscles within the motor trigeminal nucleus of the rat: a horseradish peroxidase study.

The topographical representation of the masticatory muscles of the rat was investigated by studying retrograde transport of horseradish peroxidase (HRP) from individual muscles. Contrary to the classically accepted scheme, the temporalis and masseter are separately represented dorsolaterally, the pterygoids dorsomedially and the jaw-opening mylohyoid and anterior belly of digastric ventrally within the motor nucleus, corresponding to the arrangement of the muscles on the head. Phylogenetic and ontogenetic justifications for this organization are adduced.