Different Responses of Nitric Oxide Synthase Inhibition on Morphine-Induced Antinociception in Male and Female Rats Publisher



Hosseini M¹ ; Taiarani Z² ; Hadjzadeh MAR¹ ; Salehabadi S² ; Tehranipour M² ; Alaei HA³
Source: Pathophysiology Published:2011

Abstract

The roles of gonadal hormones and nitric oxide on pain perception and their interaction have been widely investigated. In the present study the chronic effect of l-NAME (NOS inhibitor) on morphine-induced antinociception in male and female rats was investigated. Forty rats were divided into four groups: (1) female (2) female-LN (3) male (4) and male-LN. The animals of groups 2 and 4 received daily injection of l-NAME (10. mg/kg) during 3 weeks. The animals of control groups 1 and 3 received 2. ml/kg saline instead of l-NAME. Finally, all animals were tested on the hot plate test (52. ± 0.2. °C; Cut-off 80. s) to evaluate the antinociceptive effects of morphine. The hot plate test was performed for base record 15. min before the injection of morphine (10. mg/kg; s.c.) and consequently it was repeated every 15. min after the injection. There were no significant differences in baseline latencies among all groups. Reaction times after injection of morphine in female-LN were higher than in the female control group (p< 0.01). There was, however, no significant difference between male control and male-LN groups. Reaction times in the female-LN group were significantly higher than in the male-LN group. Reaction times after injection of morphine in the male group was longer than in the female group (p< 0.01). It is concluded that sex hormones such as testosterone and estrogen have a role in pain perception and analgesia. NO has a modulatory effects on functions of sex hormones in pain perception and analgesic effects of opioids. © 2010 Elsevier Ireland Ltd.