Fig. 6.

Antinociception produced by microinjection of carbachol in the LH was blocked by microinjection of cobalt chloride or L-703,606 in the RVM. (A) Following a baseline measurement at −20 min, carbachol was microinjected into the LH, and tail flick latencies were measured at −15, −10, and −5 min. Either cobalt chloride (n = 5), L-703,606 (n = 5) , or saline (n = 5) was injected into the RVM at time 0. For comparison purposes only, the open triangles illustrate response latencies when saline alone was microinjected into the LH at times 5–30 (data from Fig. 2). Mean latency values ± S.E.M. are plotted on the ordinate as a function of time min. (B) Cobalt chloride microinjected near into the RVM also blocked LH-mediated antinociception on the foot withdrawal test for the hind paws (closed squares) compared to saline microinjection into the RVM (open squares).