Résumé
Objectives: Centrally-acting antitussives with inhibitory effects on G protein-coupled inwardly rectifying potassium (GIRK) channels have been shown to also inhibit methamphetamine-induced hyperactivity in mice. In this study, we examined if cloperastine, which is the most potent inhibitor of the GIRK channels among antitussives, is sensitive to the expression levels of GIRK channels in the brain of methamphetaminetreated mice. Materials and Methods: The brain tissues have been removed and the total RNA has been extracted from tissues. The mRNA levels were evaluated using semiquantitative reverse transcription-polymerase chain reaction. Results: The concentration levels of the mRNA of GIRK channels within the ventral midbrain of methamphetamine-treated mice increased as compared with that in control and cloperastine reduced an upregulation in GIRK2, one of the subunits of the GIRK channels, by the injection of methamphetamine. Conclusion: These findings suggest that cloperastine might ameliorate hyperactivity by inhibiting the GIRK channels in the brain.
Résumé
Objective To observe the protective effects of fluoxetine on working memory impairment induced by chronic cerebral ischemia and further explore its mechanism in rats. Methods The rat model of chronic cerebral ischemia was made by surgical ligation of the bilateral carotid artery. 44 male Sprague Dawley rats were divided into sham group (n = 10) , ischemic model group (ra = 12), ischemic + fluoxetine group (n = 12) , and sham + fluoxetine group (n = 10). Fluoxetine was administered by gavage after 1 week of ischemic surgery and continued for 4 weeks. The sham group and the ischemic model group were given the same volume of 0. 9% saline. The performance of working memory was tested by a modified Morris water maze experiment that lasted for 4 days. The expression of neuronal nuclei (NeuN) , S-100(3, G protein gated inwardly rectifying K channels 1,2, and 3 ( GirKl , 2 , and 3 ) , and sorting nexin 27 ( SNX27 ) in the prefrontal cortex ( PFC) of rats were tested by Western blot, and compare between groups. Results (1) There was no significant difference in swimming speed among the four groups ( P > 0.05 ). In the training experiment, there was no significant difference among the four groups in the escape latency and the swimming distance ( both P > 0.05 ). In the memory retention test, the escape latency of rats in the ischemic model group was significantly increased on 2nd, 3rd and 4th day compared with the sham group (day2: [48.2 ±6. 3] s vs. [27.4±4.0]s, day 3 :[53.9 ±6.4] s vs. [29.4±6.3]s, day4: [41.4± 4. 9] s vs. [23.8 ±3.7] s; all P 0.05). (3) There was no significant difference in the membrane expression of GirKl protein among the four groups (P > 0. 05). Taking the sham group as a reference and the relative grey value of GirK2 and GirK3 is defined as 1, the relative grey values of GirK2 in the ischemia model group and the ischemia + fluoxetine group were 1. 27 ± 0. 07 and 1. 06 ±0.06, the relative grey values of GirK3 in the ischemia model group and the ischemia + fluoxetine group were 1.23 ±0.08 and 1.00 ±0.06. The membrane expression of GirK2 and GirK3 in the ischemic model group was higher than that in the sham group. The membrane expression of GirK2 and GirK3 in the ischemic + fluoxetine group was down-regulated compared with the ischemic model group ( both P < 0. 05). (4) Taking the sham group as a reference and the relative grey value of SNX27 in the sham group is defined as 1, the relative grey values of SNX27 in the ischemia model group, the ischemia + fluoxetine group, and the sham + fluoxetine group were 0. 78 ± 0.09, 0.97 ± 0.04, and 0. 94 ±0.05, respectively. The expression of SNX27 in the ischemic model group was lower than that in the sham group, and the down-regulation of SNX27 expression in the ischemic model group was reversed after fluoxetine treatment (P<0. 05). Conclusion Fluoxetine can ameliorate working memory impairment of rats induced by chronic cerebral ischemia, which may partly reverse the increase of surface expression of GirK2 and GirK3 in the prefrontal cortex through acting on SNX27.