Effects of α1-adrenoreceptor antagonism on Fos protein expression in magnocellular and parvocellular cells in morphine-dependent and morphine-withdrawn rats. Mean + SEM number of Fos-IR cells in the SON, the magnocellular paraventricular nucleus (MPVN), and the parvocellular paraventricular nucleus (PPVN). Morphine-naïve (NAIVE) and morphine-dependent (DEPENDENT) rats were pentobarbitone-anesthetized, infused for 2 hr with 0.15 msaline (intracerebroventricularly; VEH) or benoxathian (5 μg/min, i.c.v.; BEN), and decapitated 90 min after administration of naloxone (5 mg/kg, i.p., 30 min into the intracerebroventricular infusion; n = 5–7). *p < 0.05 versus morphine-naïve vehicle-infused rats; †p < 0.05 versus morphine-naïve benoxathian-infused rats; one-way ANOVA on ranks, followed by Dunn's method.