Abstract: (1785 Views)
Background and Aim: Opioids are known as the first line of pain relief medications in patients with chronic pain. Frequent use of morphine reduces its analgesic effects in patients, which inevitably leads to an increase in its dosage. One of the most important mechanisms involved in morphine is the reduction of the inhibitory effect of GABAergic interneurons. The aim of this study was to investigate the effects of GABA agonists on morphine antinociception in acute and chronic pain induced by formalin test.
Material and Method: 42 male Wistar male rats were divided into 7 groups, randomly: 1- Control 2- Single dose of morphine, 3- Morphine tolerance 4- Single injection of muscimol. 5- Single injection of baclofen 6- GABAA agonist (Musimol) + Morphine 7- GABAB agonist (Baclofen)+Morphine. GABA agonists were injected intraperitoneally one day before induction of morphine tolerance and on days 1, 3, 5, 7. On the eighth day, morphine analgesic tolerance was measured by formalin test.
Results: The results showed that muscimol and baclofen (at subtherapeutic dose 0.5 mg/kg) could reduce pain behaviors in the first and second phases of formalin test.
Conclusion: These results show that GABA neurotransmitter reduces morphine tolerance when intraperitoneal injection of GABA with effect on type A or B receptors will compensate for this decrease and increase the morphine antinociceptive effect.
Type of Study:
Research |
Subject:
Special Received: 2018/06/7 | Accepted: 2018/08/10 | ePublished: 2019/04/15