Changes in acid phosphatase activity in the substantia gelatinosa in response to pain.

Two-day and 15-day-old offspring of capsaicin-pretreated Wistar rats were given subcutaneous injections of a 5% formalin solution to the dorsal aspect of the right forepaw. One hour after injection, acid phosphatase activity of the substantia gelatinosa of formalin/capsaicin cervical sections was significantly greater bilaterally than in saline/capsaicin 15-day-old animals. In 2-day-old animals the formalin/control right cervical sections had significantly higher acid phosphatase activity than saline/control. These results are further support for a direct functional relation between activity in the substantia gelatinosa and chemogenic pain stimulus.