Introduction: Methadone has been used as a drug to detoxify opioid tolerance. Naloxane
precipitated morphine withdrawal behaviours were attenuated by venlafaxine as an antidepressant.
On the contrary, after detoxifying the opioids, spontaneous withdrawal syndrome may occur with
pain sensitivity. Therefore the present study aimed to examine the effects of chronic methadone
(70 mg/kg, in drinking water, 7 days), venlafaxine (80 mg/kg/day, intraperitoneally, 7 days) and
their combinations with the spontaneous morphine withdrawal syndrome and pain sensitivity.
Methods: Twenty eight young male Sprague-Dawley rats were randomly divided into 4
groups: control, venlafaxine treated, methadone treated and venlafaxine + methadone treated.
Morphine sulfate (10 mg/kg/day, subcutaneously, 4 days) was injected to all animals. Then
primary withdrawal behaviours and tail flick test were performed. The test was then followed
by methadone or its vehicle administration. Second intervention was venlafaxine or its vehicle
injection. Then final withdrawal behaviours and tail flick test were performed.
Results: Combination of chronic methadone substitution and venlafaxine administration,
significantly reduced freezing behaviour of spontaneous morphine withdrawal syndrome
(p<0.01, 379±144%). Chronic methadone administration (p<0.05, 35±8% difference with
venlafaxine treated group) induced hyperalgesia. A positive correlation (p=0.001, +63%) was
observed between the animals final freezing scores and their response latencies to the painful
stimulus.
Discussion: Combination of chronic methadone and venlafaxine administrations reduces
freezing withdrawal behaviour. Further investigations on analgesic interventions are needed to
overcome this hyperalgesia.
نوع مطالعه:
Original |
موضوع مقاله:
Behavioral Neuroscience دریافت: 1393/1/21 | پذیرش: 1393/7/17 | انتشار: 1393/10/11