Effects of leukotriene synthesis inhibition on acute liver damage induced by carbon tetrachloride

Administration of the leukotriene synthesis inhibitors nordihydroguaiaretic acid (NDHGA, 30 mg/kg), caffeic acid (20 mg/kg) or nafazatrom (100 mg/kg) and of the phosphodiesterase inhibitor and free radical trapper dipyridamole (10 mg/kg) prevented the alterations in enzyme activity displayed by acute CCl4 administration. The effect was less evident in preventing hepatic glycogen depletion or lipid peroxidation. A synergistic protective effect between dipyridamole and NDHGA or caffeic acid was observed. In conclusion, the present results show that acute hepatic damage induced by CCl4 can be partially prevented by leukotriene synthesis inhibitors and the protection is enhanced with the simultaneous use of phosphodiesterase inhibitors.

Angiotensin-II type 1 receptor (AT1R) and alpha-1D adrenoceptor form a heterodimer during pregnancy-induced hypertension

Pregnancy courses with low response to angiotensin II and adrenergic agonists. In preeclampsia, both effects are reverted. It is known that angiotensin II regulates adrenergic system. It is not known, however, the interaction between both systems receptors. Our aim was to study if AT(1)R and alpha1D adrenoceptor heterodimerize in preeclampsia. We used subrenal aorctic coarctation in pregnant rats. Aortic tissues were prepared for confocal imaging and coimmunoprecipitated for alpha1D and AT(1) receptors. We found that AT(1)R and alpha1D adrenoceptor heterodimerize in both, healthy and preeclamptic groups. In healthy pregnant rats, heterodimer is barely detected. In preeclamptic rats however, we found higher heterodimerization. These results suggest that AT(1)R and alpha1D -adrenoceptor may form heterodimers, and may play a role in preeclampsia.

Effects of exercise on oxidative stress in rats induced by ozone

Oxidative stress (OS) induced by acute exercise is reduced by chronic exercise. Ozone (O₃) exposure produces OS. The aim of this study was to determine if aerobic exercise (AE) reduced OS produced by O₃. A pilot experiment was performed with male Wistar rats submitted to AE (trained to swim 90 min/day). Adaptation to exercise was demonstrated three weeks after training by means of changes in reduced nitrates (NO_x) in plasma. Therefore, two-week training was chosen for the following experiments. Six of twelve trained rats were exposed to O₃ (0.5 ppm, 4 h/day, one hour before exercise). Two groups of sedentary animals (n = 6 each) were used as controls, one of which was exposed to O₃. At the end of the experiments NO_x, 8-isoprostane (8-IP), malondialdehyde (MDA), superoxide dismutase (SOD) activity, and carbonyls (CBs) were measured in plasma. CBs did not change in any group. O₃-induced OS was manifested by reduced NO_x and SOD activity, as well as increased 8-IP and MDA. Exercise significantly blocked O₃ effects although SOD was also decreased by exercise (a greater drop occurring in the O₃ group). It is concluded that AE protects against OS produced by O₃ and the effect is independent of SOD.

Striatal input- and rate-dependent effects of muscarinic receptors on pallidal firing

The globus pallidus (GP) plays a key role in the overall basal ganglia (BG) activity. Despite evidence of cholinergic inputs to GP, their role in the spiking activity of GP neurons has not received attention. We examine the effect of local activation and blockade of muscarinic receptors (MRs) in the spontaneous firing of GP neurons both in normal and ipsilateral striatum-lesioned rats. We found that activation of MRs produces heterogeneous responses in both normal and ipsilateral striatum-lesioned rats: in normal rats the response evoked by MRs depends on the predrug basal firing rate; the inhibition evoked by MRs is higher in normal rats than in striatum-lesioned rats; the number of neurons that undergo inhibition is lower in striatum-lesioned rats than in normal rats. Our data suggest that modulation of MRs in the GP depends on the firing rate before their activation and on the integrity of the striato-pallidal pathway.