Summary
In anesthetized cats, mostly spinalized at C1/C2, the thoracic and lumbar sections of the vertebral canal were selectively heated or cooled. Single unit activity was recorded with steel microelectrodes from the spinal cord at the level of C2 to C4. The positions of the electrode tips were determined by micromarking.
The existence of two groups of temperature dependent ascending spinal units was confirmed. One group of units was activated by spinal cord cooling below normal body temperature. The other group was activated by spinal cord heating. No temperature dependent neurons were found, so far, exhibiting maximum discharge rates at normal body temperature. A roughly proportional relation between discharge rate and vertebral canal temperature seemed to exist in both heat sensitive and cold sensitive units within a limited range of spinal hyperthermia or hypothermia respectively. Part of the units exhibited dynamic responses to changes of vertebral canal temperature in addition to their static responses.
As determined by micromarking, heat sensitive and cold sensitive ascending spinal units were conducted in the anterolateral tracts. Both types of units were observed also under neuromuscular blockage. It is concluded that the temperature dependent ascending spinal neurons are transmitting signals from basically afferent spinal thermosensitive structures existing as two functionally different sets, one heat sensitive and one cold sensitive.
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Simon, E., Iriki, M. Sensory transmission of spinal heat and cold sensitivity in ascending spinal neurons. Pflugers Arch. 328, 103–120 (1971). https://doi.org/10.1007/BF00592439
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DOI: https://doi.org/10.1007/BF00592439