Primate spinothalamic cell responses to ureteral occlusion.

Experiments were done to examine the effect of occlusion of the uppermost portion of the ureter on activity of spinothalamic tract (STT) neurons. Fifteen monkeys (Macaca fascicularis) were anesthetized with alpha-chloralose. Extracellular unit recordings were obtained from 38 STT neurons in the T11-L1 segments. All cells were excited by renal A delta-afferent fibers or by both A delta- and C-fibers. In addition each cell had a somatic receptive field, most commonly located on the left flank and abdomen. Ureteral occlusion increased activity of 16 cells from 4 +/- 1 to a peak of 32 +/- 9 spikes/s. Peak responses occurred, on average, 3 s following the onset of occlusion. Thereafter activity adapted to a lower level. Cells that responded to ureteral occlusion were most often wide dynamic range cells and were significantly more likely to receive both A delta- and C-fiber renal input than the cells that failed to respond. In addition responses of cells with A delta- and C-fiber inputs were significantly greater than cells with only A delta-input. Responsive cells were located primarily in laminae V and VII. Results of these experiments show that occlusion of the uppermost portion of the ureter excites thoracolumbar STT cells. These cells probably play a role in pain of renal origin, including its referral to the flank and abdomen.