We thank the correspondents for their interest in our work and the Journal for the opportunity to respond.Addressing the first concern, while we have done studies in rats with this model,1'2 in our recently published study3 we used mice, a species that we have reported on in this behavioral paradigm many times before.4"12 In addition, this behavioral paradigm has been used by other laboratories to good effect.13'14 Next, we need to clarify a timeline issue that appears to have confused the correspondents. As indicated in figure 1 and elaborated in the narrative (p. 1162, first column) the mice are only exposed to a foot-shock during the -training session before surgical manipulation. Therefore, possible surgical injury to nociceptive nerves that transmit the foot-shock does not pertain. The correspondents' concern about the influence of surgery-induced nociception on aver-sive motile behavior should be allayed by the facts that (1) we routinely provide postoperative analgesia with buprenor-phine response (p. 1161, second column), and, (2) motility is unaffected by surgery.6 We disagree with the correspondents' contention we may be overstating the effect of surgery in our freezing time experiments. Were the surgical phenotype to be affected by pain-related immobility, then we should see more rather than less freezing time; therefore, if anything, we may be understating the influence of surgery on freezing time.
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