Figure 4.

Bradykinin sensitizes activation of neurons by morphine and naloxone. Repetitive activation of DRG neurons elicited by 40 s applications of morphine and naloxone. Bradykinin reversibly sensitized calcium influx evoked by both morphine (n = 111) and naloxone (n = 91) but did not evoke a response when applied alone 40 s prior to morphine or naloxone. Bars indicate application periods; data are presented as mean ± SEM. The lower panel summarizes the calcium increases normalized to individual responses to 60 mM KCl. *p < 0.05