Journal of neurophysiology
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Recordings were made from spinothalamic tract (STT) cells in the lumbosacral enlargement of anesthetized monkeys. The cells were identified by antidromic activation from the contralateral ventral posterior lateral nucleus of the thalamus. Electrical stimulation at sites within the periaqueductal gray, the adjacent midbrain reticular formation, or the deep layers of the tectum were found to inhibit the activity of STT cells. ⋯ However, even when there was an interruption of the entire lateral funiculus on the side of an STT cell and of the dorsal quadrant of the contralateral side, there was still substantial inhibition following stimulation in either brain stem site. It is concluded that while part of the inhibition is mediated by pathways descending in the dorsal lateral funiculus (DLF), at least some depends on pathways coursing through the ventral spinal cord. Inhibition of STT cells may contribute to the neuronal mechanism of the analgesia that results from stimulation in the periaqueductal gray matter in awake, behaving animals.