Fiber projections from trigeminal nucleus caudalis in primate (squirrel monkey and baboon)

Abstract
Small radiofrequency lesions were produced in the trigeminal nucleus caudalis and adjacent lateral reticular formation (LRF) in seven squirrel monkeys and four baboons. Frozen brain sections were stained for cellular morphology and for axonal and terminal degeneration. The lesions in pars marginalis and gelatinosa produced terminal degeneration in pars magnocellularis and LRF. Pars magnocellularis lesions produced degeneration into the ascending trigeminal intranuclear tract and the adjacent lateral reticular formation. Ascending thalamic and reticular projections emanated from LRF lesions. These observations suggest that elements of the LRF adjacent to the nucleus caudalis are an integral part of the trigeminal somesthetic fiber projection system and may subserve the perception of noxious stimuli.