title: Different responses of nitric oxide synthase inhibition on morphine-induced antinociception in male and female rats.
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 (10mg/kg) during 3 weeks. The animals of control groups 1 and 3 received 2ml/kg saline instead of l-NAME. Finally, all animals were tested on the hot plate test (52±0.2°C; Cut-off 80s) to evaluate the antinociceptive effects of morphine. The hot plate test was performed for base record 15min before the injection of morphine (10mg/kg; s.c.) and consequently it was repeated every 15min 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.
authors.affiliation: Department of Physiology and Pharmacological Research Center of Medicinal Plants, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Hosseini
authors.forename: Zahra
authors.initials: Z
authors.lastname: Taiarani
authors.forename: Mosa Al-Reza
authors.initials: MA
authors.lastname: Hadjzadeh
authors.forename: Soodabeh
authors.initials: S
authors.lastname: Salehabadi
authors.forename: Maryam
authors.initials: M
authors.lastname: Tehranipour
authors.forename: Hojjat Allah
authors.initials: HA
authors.lastname: Alaei