Antidepressant-like effects of tramadol and other central analgesics with activity on monoamines reuptake, in helpless rats
Rojas-Corrales MO, Berrocoso E, Gibert-Rahola J, Mico JA.
Unit of Neuropsychopharmacology,
Department of Neuroscience,
Faculty of Medicine, University of Cadiz. Plz Fragela 9,
11003, Cadiz, Spain
Life Sci 2002 Nov 29;72(2):143-152


Affective states are regulated mainly by serotonin and noradrenaline. However the opioid system has been also related to antidepressant-induced mood improvement, and the &mgr;-opioid receptor has been involved in affective responses to a sustained painful stimulus. Similarly, antidepressant drugs induce an antinociceptive effect via both the monoaminergic and opioid systems, probably involving sensorial and affective dimensions of pain. The aim of this study was to test three opiate analgesics, which also inhibit monoamine reuptake, in the learned helplessness model of depression in rats. Helpless rats receiving (+/-)tramadol (10, 20 mg/Kg) or (-)methadone (2, 4 mg/Kg) showed a decreased number of failures to avoid or escape aversive stimulus (shock) in both the second and the third daily sessions, compared with controls. Rats receiving levorphanol (0.5, 1 mg/Kg) showed a decreased number of such failures in the third session. The number of crossings in the intertrial interval (ITI) was not significantly modified by (+/-)tramadol or (-)methadone. Levorphanol enhanced ITI crosses at 1 mg/Kg. These results, together with other clinical and experimental data, suggest that analgesics with monoaminergic properties improve mood and that this effect may account for their analgesic effect in regulating the affective dimension of pain. From this, it seems probable that the analgesic effect of opiates could be induced by adding together the attenuation produced of both the sensorial and the affective dimensions of pain.
Tramadol: structure
The tramadol option
Tramadol: metabolites
Tramadol and analgesia
Tramadol and acute pain
Tramadol as an antidepressant
Tramadol: risk/benefit analysis
Tramadol versus buprenorphine
Methadone for tramadol addicts?
Depression, opioids and the HPA
Pharmacokinetics and pharmacodynamics
Morphine: a mood-brightening smart-drug?
Tramadol, depression and Parkinson's disease

and further reading

Future Opioids
BLTC Research
Utopian Surgery?
The Abolitionist Project
The Hedonistic Imperative
The Reproductive Revolution
Critique of Huxley's Brave New World

The Good Drug Guide
The Good Drug Guide

The Responsible Parent's Guide
To Healthy Mood Boosters For All The Family