Skin cooling attenuates rat dorsal horn neuronal responses to intracutaneous histamine.

Itch sensation is reduced by cooling the skin. We tested whether lowering skin temperature attenuates responses of spinal dorsal horn neurons elicited by intracutaneous (i.c.) microinjection of histamine in anesthetized rats. Cooling the skin to 3 degrees C significantly and reproducibly reduced (to a mean of 48%) i.c. histamine-evoked responses in 20 of 24 wide dynamic range-type dorsal horn neurons. Histamine-evoked responses recovered to control levels after rewarming the skin. Assuming that such neurons play a role in signaling itch, depression of their responses during skin cooling may account for the psychophysical observation that skin cooling relieves itch in humans.