Interaction of the dopaminergic and Nociceptin/Orphanin FQ on central feed intake regulation in chicken

1. The aim of the current study was to determine the effects of the central dopaminergic system on N/OFQ-induced feed intake in 3-h feed-deprived neonatal broilers. 2. In experiment 1, chicken received intracerebroventricular (ICV) injections of a control solution, SCH 23 390 (D1 receptors antagonist, 5 nmol), N/OFQ (16 nmol) or their combination (SCH23 390 + N/OFQ). In experiment 2, a control solution, AMI-193 (D2 receptors antagonist, 5 nmol), N/OFQ (16 nmol) or their combination (AMI-193 + N/OFQ) were ICV injected into chickens. In experiment 3, birds received ICV injections of a control solution, NGB2904 (D3 receptors antagonist, 6.4 nmol), N/OFQ (16 nmol) and co-injection of NGB2904 + N/OFQ. In experiment 4, ICV injections of the control solution, L-741,742 (D4 receptors antagonist, 6 nmol), N/OFQ (16 nmol) or their combination (L-741,742 + N/OFQ) were applied to broilers. In experiment 5, birds were ICV injected with control solution, L-DOPA (dopamine precursor, 125 nmol), N/OFQ (16 nmol) and L-DOPA + N/OFQ. Cumulative feed intake was recorded until 120 min after injection. 3. According to the results, ICV injection of N/OFQ significantly increased feed intake (P < 0.05). Co-injection of N/OFQ and D1 receptor antagonist (SCH 23390) amplified hyperphagic effect of N/OFQ (P < 0.05). The N/OFQ-induced feed intake was increased by the D2 receptor antagonist (P < 0.05). The hyperphagic effect of N/PFQ was weakened by co-injection of L-DOPA + N/OFQ (P < 0.05). 4. These results suggested that an interaction exists between dopamine and N/OFQ via D1 and D2 receptors on central feed intake in neonatal broiler chickens.

Permethrin-induced oxidative damage in liver of rainbow trout (Oncorhynchus mykiss) and its attenuation by vitamin C

The objective of this study was to investigate the propensity of permethrin (PTN) to induce oxidative stress and changes in enzyme activities in liver of rainbow trout and its possible attenuation by vitamin C. Forty-eight fish were randomly assigned to 1 of 6 treatment groups and their livers were used for liver perfusion method: control (0 µgL(-1) permethrin and 0 mgL(-1) vitamin C), PTN-0.16 (0.16 µgL(-1) permethrin), PTN-0.32 (0.32 µgL(-1) permethrin), PTN-0.64 (0.64 µgL(-1) permethrin), Vit. C (17.2 mgL(-1) vitamin C), and PTN-0.64 + Vit. C (0.64 µgL(-1) permethrin and 17.2 mgL(-1) vitamin C). Results obtained showed that permethrin significantly (P<0.05) increased ALT, AST and LDH activities in the liver perfusion medium and malondialdehyde (MDA) level in liver tissue. The values of reduced glutathione (GSH) and total antioxidant capacity (FRAP) in the liver tissue were significantly decreased due to permethrin administration. Pearson's correlation analysis revealed a positive correlation between MDA concentration and ALT, AST and LDH activities in the permethrin groups, suggesting that the enhanced lipid peroxidation may be linked to hepatic damage caused by permethrin. On the other hand, treatment with vitamin C in the PTN-0.64 + Vit. C group increased the values of GSH and FRAP, and decreased the level of MDA and the activities of hepatic enzymes, when compared to the PTN-0.64 group. The present study revealed that vitamin C could ameliorate permethrin-induced oxidative damage by decreasing lipid peroxidation and altering antioxidant defense system in liver of rainbow trout.

Methylmercury-induced oxidative stress in rainbow trout (Oncorhynchus mykiss) liver: ameliorating effect of vitamin C

The present study was undertaken to evaluate methylmercury-induced alterations in hepatic enzymes and oxidative stress markers in liver tissue of rainbow trout (Oncorhynchus mykiss) by using a perfusion method, and to explore possible protective effect of vitamin C against these alterations. Forty-eight fish were divided into six groups containing control, test, and amelioration groups. The liver of fish in the test groups were exposed to different doses of methylmercury, i.e., 0.6, 1.2, and 2.4 μg L(-1), respectively, for 120 min. In the amelioration group, liver was treated with vitamin C (17.2 μg L(-1)) along with high dose (2.4 μg L(-1)) of methylmercury. The results of the present study showed that exposure with 0.6, 1.2, and 2.4 μg L(-1) of methylmercury significantly increased (p < 0.05) hepatic enzyme activities (alanine transaminase (ALT), aspartate transaminase (AST), and Lactate dehydrogenase (LDH)) and malondialdehyde (MDA) level, as a marker of lipid peroxidation. On the other hand, the concentration of reduced glutathione (GSH) and total antioxidant capacity of the liver decreased (p < 0.05) in the methylmercury-exposed groups when compared to the control group. Pearson's correlation analysis revealed a positive correlation between MDA concentration and ALT, AST, and LDH activities in the methylmercury groups, suggesting that the enhanced lipid peroxidation may be linked to hepatic damage caused by methylmercury. Treatment with vitamin C in methylmercury-exposed group led to a significant decrease (p < 0.05) in MDA concentration and hepatic enzyme activities and significant increase (p < 0.05) in levels of GSH and total antioxidant capacity. The values of measured parameters in the methylmercury + vitamin C group were comparable to those of the control group. The results of the present study demonstrated that methylmercury exposure induces oxidative stress in the liver of rainbow trout and treatment with vitamin C can protect fish liver against this oxidative insult.

Transcriptional activation of the oxytocin promoter by oestrogens uses a novel non-classical mechanism of oestrogen receptor action

Transcriptional activation of the gene coding for the neuropeptide hormone oxytocin by oestrogens does not follow the classical model of oestrogen receptor action. The oxytocin promoter does not contain an oestrogen response element (ERE), but instead a high-affinity binding site for nuclear orphan receptors. In the present study, the oestrogen-dependent up-regulation of the bovine oxytocin promoter is investigated in MDA-MB 231 cells. Control by oestrogen is shown to be dependent on the integrity of the nuclear orphan receptor binding site and the presence of ligand-activated oestrogen receptor, but independent of oestrogen receptor binding to DNA. Partial agonists tamoxifen and raloxifen and the pure antagonist ICI 182 780 all show agonistic activities on transcription, while exhibiting normal binding affinities to oestrogen receptor (ER)alpha. Nuclear orphan receptors oestrogen receptor-related receptor alpha (ERRalpha) and germ cell nuclear factor (GCNF) are expressed to significant levels in MDA-MB 231 cells. Binding of ERRalpha to the oxytocin promoter binding site can be demonstrated, suggesting the involvement of this nuclear orphan receptor in oestrogen-dependent up-regulation. The oestrogenic stimulation of the oxytocin promoter apparently is dependent on the stimulation of the transcriptional activity of this nuclear orphan receptor by ERK-1/ERK-2 mitogen-activated protein kinases (MAP kinases). This novel nonclassical mechanism of oestrogen action most probably is not restricted to the regulation of neuropeptide hormone expression, but may further contribute to the multitude of tissue-specific effects of oestrogenic substances.