Comment on: Abnormal contralateral pain responses from an intradermal injection of phenylephrine in a subset of patients with complex regional pain syndrome

We wish to thank Dr Shapiro for his thoughtful letter, sharing his interest in our findings of possible analgesic role of fatty acids in neuropathic pain in rodents (Pérez et al., 2004). In his letter Dr Shapiro raises the possibility that in addition to a-linolenic acid, long chain omega-3 polyunsaturated fatty acids could have been analgesic in our study. It is true that when using the general term omega-3 fatty acids, we were referring to a-linolenic acid only, as it was the only source of omega-3 in the rats’ diet. We assumed that due to the limited enzymatic conversion of a-linolenic acid to longer chain eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids (Brenna, 2002), our results could not be attributed to these polyunsaturated fatty acids. Moreover, in recent experiments we show that the consumption of oils rich in the omega-3 a-linolenic acid was associated with higher levels of heat hyperalgesia (Pérez et al., 2005). Far from being discouraged, we recognize the distinct functions of EPA and DHA and their potent effects in many physiological processes. Consequently, we are currently assessing their potential role in the prevention of experimental neuropathic pain in nerve-injured rats.