Effect of Intraperitoneal Nalbuphine-HCl on C-fos Expression in Rat Brain induced by Incisional Pain

Abstract

Background: Nalbuphine-HCI , an agonist-antagonist of receptors, has limited analgesic or sedative effects, and an effect ceiling. It is generally accepted that c-fos is a marker of neuronal activity and its expression is correlated with nerve pathways activated by nociceptive stimuli. The aim of this study was to examine the effect of nalbuphine-HCI on c-fos expression in rat brain caused by incisional pain. Methods: A 1.0 cm longitudinal incision was made through the skin, fascia, and muscle of the plantar aspect of the hind paw of male Sprague-Dawley rats (140-150 g). 2.87 mg/kg of nalbuphine-HCI was then injected intraperitoneally 1 hour before incision (pre-nubain group; N = 11) and 30 minutes after incision (post-nubain group; N = 10). Identical volumes of normal saline were injected 30 minutes after incision (control group; N = 14). Two hours later, c-fos protein expressions in the thalamus, hypothalamus, cerebral cortex, and amygdala were examined by immunohistochemistry using a specific antibody. Results: In the thalamus, fewer c-fos positive cells were observed in the experimental group than in the control (P