Activity patterns of temperature-reactive dorsal horn neurons and their reactions to peripheral receptor stimulation by Ca.

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Abstract
Unit responses of sorsal horn neurons (DHN) of rats to thermal stimulation of the scrotal skin were recorded extracellularly. Of 74 DHN, 55 increased their activity during scrotal skin warming, while the activity of 14 neurons was accelerated by cooling. Tonic activities of 3 neurons were inhibited by warming (inverse warm-reactive). Two neurons demonstrated a complex response and were activated during cooling and warming. Most of thw warm-reactive and all of cold-reactive DHN had steep sigmoid temperature-activity-relation curves with a temperature-dependent range of 1-5.degree. C. Injections of 5-10 mg/kg CaCl2 into the lower abdominal aorta produced excitation in 30 of 33 warm-reactive DHN and inhibition in 3 neurons. Only 3 of 8 cold-reactive DHN demonstrated inhibition, while the remaining 5 were activated. All 3 inverse warm-reactive neurons were inhibited. DHN which exclusively reacted to mechanical stimuli or did not respond to any peripheral stimulation were not affected by peripheral Ca administration. A number of cold-reactive DHN apparently receive inputs from warm- and cold-sensitive afferents; such double innervation may exist in some warm-reactive DHN as well.

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