Figure 2

HFS delivered to the BLA suppressed nociceptive responses recorded in the PFC. On the left, unit discharges: on the right, the histogram of single unit discharges calculated from the unit discharge. A. Unit discharges recorded in the PFC. Pre: Nociceptive responses evoked by 500 gf stimulation applied to the rat tail. At 50 min after HFS delivery to the BLA, the nociceptive responses were entirely blocked. At 90 min after HFS, nociceptive responses had recovered to the pre-HFS control level. B. Inhibitory effects of nociceptive responses were induced by HFS delivered to the BLA. The inhibitory effects of nociceptive responses appeared within 10 min and lasted longer than 60 min after HFS. The duration of the control nociceptive responses was assessed as 100% and changes in duration after HFS to the BLA were converted into percentages of the control value. n = 9. *p < 0.05, versus the pre-HFS control value, **p < 0.001, versus the pre-HFS control value. Error bars represent S.E. C. The mean discharge frequency of the control nociceptive responses was assessed as 100% and changes in mean discharge frequency after HFS to the BLA were converted into percentages of this control value. *p < 0.05, versus the pre-HFS control value, **p < 0.001, versus the pre-HFS control value. Error bars represent S.E. Mean discharge frequency of nociceptive responses also decreased after HFS in the same manner as the response duration. The statistical significance of differences between results obtained by the two methods was calculated using ANOVA. There were no significant differences between the mean discharge frequency of responses changes (n = 9) and response duration changes (n = 9).