Autoradiographic study on etorphine and phencyclidine specific binding sites in rabbit mesenteric artery

Autoradiography was used to study the localization of kappa and PCP/sigma receptors in the blood vessels. Slices of rabbit mesenteric arteries were incubated with 0.4 nmol/L [3H]etorphine or/and 10 mumol/L etorphine for 45 min at 25 degrees C, or incubated with 5.2 nmol/L [3H]PCP or/and 20 mumol/L PCP for 60 min at 4 degrees C. Then, slices were covered with emulsion coated coverslip and kept for 8-10 wk at 4 degrees C. The results were as follows: Microscopy Autoradiographic analysis indicated that etorphine and PCP specific binding sites were both located in the outer-layer and the smooth muscle of the artery. However, most of these binding sites were lost in the 6-OHDA pretreated arteries in which the adrenergic nerve endings were destroyed. Microspectrophotometry The absorbance (A) of [3H]etorphine autoradiographic density for total binding (TB) and nonspecific binding (NSB) in control group were 0.416 +/- 0.056 and 0.044 +/- 0.011, respectively (P less than 0.01), and for TB after incubation with 6-OHDA was 0.068 +/- 0.013 which was different from the A value of TB in the control (P less than 0.01). The A value of [3H]PCP autoradiographic density for TB and NSB in the control were 0.546 +/- 0.087 and 0.023 +/- 0.060, respectively (P less than 0.01), and for TB after incubation with 6-OHDA was 0.065 +/- 0.015 which was significantly less than that of TB in the control group (P less than 0.01).