Figure 3.
Capsaicin-evoked release of CGRP from minced lumbar sections obtained from the ipsilateral dorsal quadrants of rats undergoing sham or SNL surgery (A), which received control serum or anti-dynorphin antiserum (B), previous lesions of the DLF (3 d before sham or SNL surgery) at T8 (C), or were pretreated 38 d previously with RVM saporin (SAP), dermorphin (DERM), or dermorphin-saporin conjugate (D; Derm-Sap). After a 45 min equilibration period in the perfusion chambers, followed by a 12 min collection of perfusate for determination of baseline values, capsaicin (1 μm) was added to the perfusion medium. CGRP content was quantified by radioimmunoassay. Evoked release was defined as the amount of CGRP above the basal values, and data are shown as percentage of the evoked release from sham-operated rats in the same assay. Capsaicin-evoked CGRP release did not differ between the sham-operated rats SNL rats on postsurgery day 2. In contrast, tissue from SNL rats demonstrated a significantly (*p ≤ 0.05) enhanced capsaicin-evoked CGRP release relative to the sham-operated group on postsurgery day 10 (A). Addition of control serum (i.e., dynorphin antiserum with IgG removed) to the perfusate to achieve a concentration of 1 mg/100 ml had no significant effect on capsaicin-evoked release in either the sham-operated or SNL groups. Addition of dynorphin antiserum (1 mg/100 ml) to the perfusate prevented the enhanced evoked CGRP release in SNL tissues (B). The capsaicin-evoked release of CGRP from the sham DLF/SNL group was significantly (*p ≤ 0.05) greater than that of the sham DLF/sham SNL group. Capsaicin-evoked CGRP release in DLF/SNL rats was not significantly different from that of the sham SNL/DLF lesions. Capsaicin evoked CGRP release in DLF/sham SNL lesion did not differ from that in sham DLF/sham SNL rats (C). Tissues from rats with SNL that were pretreated with either saporin or dermorphin in the RVM demonstrated a significantly greater (*p ≤ 0.05) capsaicin-evoked CGRP release than those tissues taken from rats with the same RVM pretreatment and sham surgery. In contrast, RVM pretreatment with dermorphin-saporin prevented the SNL-induced enhancement of capsaicin-evoked CGRP release in tissues from SNL rats. The capsaicin-evoked release of CGRP from the SNL group pretreated with the dermorphin-saporin conjugate was not different from that of the sham-operated group and was not different from that seen in tissues from RVM saline-pretreated sham-operated rats. The data were converted to percentage of the evoked release from sham-operated rats to account for interassay variability. n = 4-20 rats per group.