BackgroundOur objective is to determine the activity of the antioxidant defense system at admission in patients with early onset first psychotic episodes compared with a control group.MethodsTotal antioxidant status (TAS) and lipid peroxidation (LOOH) were determined in plasma. Enzyme activities and total glutathione levels were determined in erythrocytes in 102 children and adolescents with a first psychotic episode and 98 healthy controls.ResultsA decrease in antioxidant defense was found in patients, measured as decreased TAS and glutathione levels. Lipid damage (LOOH) and glutathione peroxidase activity was higher in patients than controls. Our study shows a decrease in the antioxidant defense system in early onset first episode psychotic patients.ConclusionsGlutathione deficit seems to be implicated in psychosis, and may be an important indirect biomarker of oxidative stress in early-onset schizophrenia. Oxidative damage is present in these patients, and may contribute to its pathophysiology.

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The ability of pindolol, a beta-adrenoceptor blocker/5-hydroxytryptamine(1A/1B) antagonist, to enhance the clinical antidepressant response to selective serotonin re-uptake inhibitors is generally attributed to a blocking of the feedback that inhibits the serotoninergic neuronal activity mediated by somatodendritic 5-hydroxytryptamine (5-HT)(1A) autoreceptors. The current study examined the ability of pindolol to enhance the analgesic effect of tramadol, an atypical centrally-acting analgesic agent with relatively weak opioid receptor affinity and which, like some antidepressants, is able to inhibit the re-uptake of 5-HT in the raphe nuclei. Racemic pindolol (2 mg/kg, s.c.), rendered analgesic a non-effective acute dose of tramadol (10-40 mg/kg, i.p.) in two nociceptive tests: a hot plate test in mice and a plantar test in rats. Moreover, (+/-)8-OH-DPAT (0.125-1 mg/kg, s.c.), a selective 5-HT(1A) agonist, reduces the analgesic effect of tramadol in the same tests. These results suggest an implication of the somatodendritic 5-HT(1A) receptors in the analgesic effect of tramadol and open a new adjuvant analgesic strategy for the use of this compound.

In the last few years, there has been a great increase in our understanding of pain mechanisms. Given the complexity of the mechanisms involved in pain modulation, it is surprising that the pharmacological control of pain through the application of relatively simple analgesics can be effective. Nevertheless, the application of single analgesics is not always effective in diverse painful conditions such as chronic pain syndromes. In these circumstances, we can take advantage of the complexity of pain regulation and try to identify new targets in these intricate processes. It is becoming clear that the combination of different mechanisms, which improves efficacy with reduced toxicity, is necessary for the reliable pharmacotherapy of pain, and is at the forefront in the search for better analgesics. Serotonin is involved at multiple levels in the regulation of nociception. In particular, the raphe nuclei may play a crucial role in integrating the nociceptive and affective information through descending projections to the spinal cord and ascending projections to the forebrain. In these nuclei, 5-HT1A receptors function as somatodendritic autoreceptors controlling the release of serotonin in terminal areas. Different studies have shown that, by preventing this inhibitory control of serotonin release, it is possible to enhance the analgesic effect of drugs that increase serotonin levels (i.e. antidepressants, opiates, and non-steroidal anti-inflammatory drugs) by facilitating descending, and also ascending, pathways involved in pain modulation. Therefore, 5-HT1A receptors may be used as a new target in the search for new pharmacological approaches in the augmentation of analgesia.

These findings suggest that 5-HT1A receptors modulate the analgesic and the antidepressant-like effects of tramadol in differing ways. The results suggest the involvement of the 5-HT1A autoreceptors from the raphe nuclei and spinal 5-HT1A receptors in the antinociceptive effect. In contrast, the 5-HT1A receptors located in the forebrain may be responsible for the blockade of the antidepressant-like effect of tramadol. 5-HT1B receptors seem not to modify these effects in the models investigated.

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Combined 5-HT and opioid properties result in a greater efficacy in antagonizing 5-HT2A-related behavior. These results provide behavioral evidence to support convergent effects of the 5-HT and opioid systems in discrete brain areas, offering the potential for therapeutic advances in the management of refractory stereotypes and compulsive behaviors.