Summary: &in, 37 (1989) 323-333
A dorsolateral spinothalamic tract in macaque monkey
A. Vania Apkarian and Charles J. Hodge
Department of N~ros~rge~, State University of New York Health Science Center, 750 East Adams Street, Syracuse,NY I321 0 (U.S.A.)
(Received 1 February 1988. revision received 29 September 1988, accepted 17 January 1989)
Summary Prior work has indicated the existence of a major spinal cord pathway made up of lamina I cell axons ascending in
the dorsolateral funiculus in both rat and cat. In cat, a portion of this lamina I dorsolateral funiculus pathway terminates in the
thalamus. The purpose of this report is to demonstrate that a similar dorsolateral spinothalamic tract exists in macaque monkey.
Retrograde transport of horseradish peroxidase, injected into the somatosensory thalamus of monkeys, was used to identify the cells
of origin of the spinothalamic tract in the cervical and lumbar enlargements. In order to determine the funicular courses of the axons
contributing to the spinothalamic pathway, thalamic injections of horseradish peroxidase were combined with ipsilateral ventral or
dorsolateral thoracic spinal cord lesions. The results indicate that in macaque monkey many lamina I cell axons ascend to the
thalamus in the dorsolateral funiculus, contralateral to their parent cells. Some lamina I cell axons as welt as the majority of axons of
spinothalamic cells located in deeper laminae ascend in the contralateral ventral quadrant to terminate in the thalamus. The existence
in macaque of a dorsolateral spinothalamic pathway comprised of lamina I cell axons strongly implies the presence of a similar
pathway in humans and has important implications regarding the mechanisms underlying both clinical and experimental nociception.