Omega-3 fatty acids prevent nicotine withdrawal-induced exacerbation of anxiety and depression by affecting oxidative stress balance, inflammatory response, BDNF and serotonin metabolism in rats.

Adolescents are known to be more vulnerable than adults to the adverse effects of nicotine dependence. In the present study, we aimed to investigate whether adolescent nicotine exposure, followed by a period of abstinence, could affect the anxiety- and depressive-like behaviors in rats. For this purpose, behavioral assessments were carried out using open field test, elevated plus maze and forced swimming test in male rats received chronic nicotine intake during adolescence followed by a period of abstinence in adulthood, compared to their control counterparts. In addition, O3 pre-treatment was done at three different doses to reveal whether it could prevent nicotine withdrawal effects. Then, animals were euthanized and the cortical concentrations of oxidative stress markers, inflammatory indices, brain-derived neurotrophic factor, serotonin and the enzymatic activity of monoamine oxidase-A were measured. Results indicated that nicotine withdrawal exacerbates the behavioral signs of anxiety through alteration of the brain oxidative stress balance, inflammatory response and serotonin metabolism. Moreover, we found that omega 3 pre-treatment significantly prevents the nicotine withdrawal-induced complications by restoration of changes in the mentioned biochemical indices. Moreover, the improving effects of O3 fatty acids were found to be dose-dependent in all experiments. Taken together, we would like to suggest the O3 fatty acids supplementation as a safe, inexpensive and effective strategy for prevention or amelioration of detrimental effects induced by nicotine withdrawal at cellular and behavioral levels.

Evaluation of the association between blood homocysteine concentration and the degree of behavioral symptoms in the 6-hydroxydopamine-induced Parkinsonism in rat.

Growing evidence indicates that homocysteine (Hcy) may be involved in the pathophysiology of several neurological disorders including Parkinson's disease. In the present study, the association between blood Hcy concentration and the degree of behavioral symptoms in the 6-hydroxydopamine (6-OHDA)-induced Parkinsonism in rat was evaluated. Total serum Hcy (tHcy) was measured before and 6 weeks after the intracerebral injection of 6-OHDA. Apomorphine-induced rotational test was performed at second, third and sixth weeks after 6-OHDA injection. Subsequently, cell replacement therapy was performed on rats with good rotation score. No correlation between tHcy in before 6-OHDA injection and severity of the rotations after 6-OHDA injection was observed. On the other hand, 6-OHDA treatment significantly decreased tHcy level. However, this reduction was only observed in animals with low degree of rotations and in rats with high number of rotations; tHcy did not change significantly. Furthermore, 10 weeks after cell transplantation, tHcy was significantly lower than that found before therapy if the rats showed good improvement in the degree of rotations. We also examined the effect of different supplements of B vitamins on tHcy before and after 6-OHDA injection. In healthy rats, all kinds of B vitamins and also supplement B6 or B12 alone reduced tHcy. Following 6-OHDA injection, B vitamin supplementation failed to cause remarkable effect. Considering the direct correlation between the severity of rotational behavior and the degree of lesion in the substantia nigra (SN), our data indicate that higher tHcy values can predict higher SN dopaminergic neurodegeneration.

Involvement of orexin-2 receptors in the ventral tegmental area and nucleus accumbens in the antinociception induced by the lateral hypothalamus stimulation in rats.

Orexin, which is mainly produced by orexin-expressing neurons in the lateral hypothalamus (LH), plays an important role in pain modulation. Both kinds of orexin-1 (Ox1) and orexin-2 (Ox2) receptors have been found at high density in the ventral tegmental area (VTA) and nucleus accumbens (NAc). However, the quantity of Ox1 receptors in the VTA is more than that in the NAc. Additionally, it seems that the functional interaction between the LH, VTA and NAc implicates pain processing and modulation. In this study, we tried to examine the involvement of Ox2 receptors in the NAc and VTA using tail-flick test as an animal model of acute pain following microinjection of effective dose of carbachol (125nmol/0.5µl saline) into the LH. In this set of experiments, different doses of TCS OX2 29 as an Ox2 receptor antagonist were microinjected into the VTA (1, 7 and 20nmol/0.3µl DMSO) and the NAc (2, 10, 20 and 40nmol/0.5µl DMSO) 5min prior to carbachol administration. Administration of TCS OX2 29 into the VTA and NAc dose-dependently blocked intra-LH carbachol-induced antinociception. However, the inhibitory effect of TCS OX2 29 as an Ox2 receptor antagonist was more potent in the VTA than that in the NAc. It seems that VTA orexinergic receptors are more effective on LH stimulation-induced antinociception and the modulation of pain descending inhibitory system originated from the LH than those of the same receptors in the nucleus accumbens in rats.

Involvement of orexin-1 receptors in the ventral tegmental area and the nucleus accumbens in antinociception induced by lateral hypothalamus stimulation in rats.

Previous studies have demonstrated that chemical stimulation of the lateral hypothalamus (LH) with carbachol has an important role in the induction of antinociception in tail-flick test as a model of acute pain. In this study, we tried to evaluate the involvement of orexin-1 receptors in the ventral tegmental area (VTA) and the nucleus accumbens (NAc) on antinociceptive responses induced by LH stimulation in rats. One hundred twenty adult male albino Wistar rats weighing 200-250g were unilaterally implanted with two separate cannulae into the LH, and VTA or NAc. Antinociceptive effects for two doses of intra-LH carbachol (125 and 250nmol/0.5µl saline), as a cholinergic agonist, were evaluated in this study. In another set of experiments, animals received intra-VTA or -NAc infusions of SB334867 as a selective orexin-A receptor antagonist (0.3, 1, 3 and 10nmol/rat), just 5min before microinjection of an effective dose of carbachol into the LH. In the tail-flick test, antinociceptive responses of drugs were obtained by tail-flick analgesiometer and represented as maximal possible effects (%MPE) at 5, 15, 30, 45 and 60min after their administrations. The results showed that unilateral intra-LH administration of carbachol (125 and 250nmol/rat) induced antinociception in rats (P<0.01). There were no significant differences between the antinociceptive effects of these two doses. In the second part of our study, intra-VTA and intra-accumbal administrations of different doses of SB334867, 5min before microinjection of carbachol, could dose-dependently prevent the development of LH stimulation-induced antinociception in rats. However, this effect was less in the NAc. It is supposed that the orexinergic projections from the LH to the VTA and NAc are direct/indirectly involved in the antinociception induced by LH chemical stimulation, and orexin-1 receptors in the ventral tegmental area have a more substantial role in this phenomenon.