Fig. 1.

The effects of intraspinal N-methyl-D-aspartic acid (NMDA) injection and sham surgery (control) on the responses to cold and mechanical stimuli delivered to the hind paws. Baseline responses were measured 3 days prior to the surgery done for intraspinal injection. Cold allodynia assessed with acetone was represented as percent response rates (A), and animals showing sustained sign of cold allodynia during the observation periods were interpreted as positive (C). Mechanical allodynia tested with calibrated von Frey filaments was expressed as withdrawal threshold (B), and animals that whose measured withdrawal threshold was less than 4 g at every testing were interpreted as positive (D). Responses to cold and mechanical stimuli were not influenced by intraspinaly injected NMDA. Data are expressed as mean ± SE or number of animals.