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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.
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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.
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Objective To evaluate the effect of intrathecal dexmedetomidine on the expression of G-protein-coupled inwardly rectifying K+ channel 1 (GIRK1) in dorsal root ganglia of rats with diabetic neuropathic pain (DNP).Methods A total of 144 healthy adult male SPF Sprague-Dawley rats,aged 8-10 weeks,weighing 200-220 g,were randomly divided into 4 groups (n =36 each) using a random number table:control group (group C),dexmedetomidine group (group D),group DNP,and DNP + dexmedetomidine group (group DD).DNP model was established by single intraperitoneal injection of streptozotocin (STZ) 60 mg/kg.In D and DD groups,dexmedetomidine 1.5 μg/kg was injected intrathecally at 14 days after citrate buffer or STZ injection,while the equal volume of normal saline was given in group C.The mechanical pain threshold was measured before STZ injection (T0),at 14 days after STZ injection (T1),and at 2,4 and 6 h after intrathecal injection (T:2-4).After measurement of the mechanical pain threshold at T2-4,the rats were sacrificed,and the dorsal root ganglia of the lumbar segment (L4-6) were removed for determination of the number of GIRK1 positive cells and expression of GIRK1 protein by immunofluorescence and Western blot,respectively.Results Compared with group DNP,the mechanical pain threshold was significantly increased,the number of GIRK1 positive cells in dorsal root ganglia was significantly increased,and the expression of GIRK1 was significantly up-regulated at T2-4 in group DD (P＜0.05).Compared with group D,the number of GIRK1 positive cells in dorsal root ganglia was significantly increased,and the expression of GIRK1 was significantly up-regulated at T2-4 in group DD (P＜0.05).Compared with group C,the mechanical pain threshold was significantly decreased at T1-4 in group DNP (P＜0.05).Conclusion Intrathecal dexmedetomidine attenuates DNP through up-regulating the expression of GIRK1 in dorsal root ganglia of rats.
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Objective: To investigate the effect with its possible mechanisms of zacopride on vasodilatation of isolated coronary arterial rings in experimental rats. Methods: The tension of vasodilatation of isolated coronary arterial rings of male SD rats was recorded by Powerlab and DMT system. The rats were divided into 4 groups: +Endo (vehicle) group, +Endo (zacopride) group and -Endo (vehicle) group, –Endo (zacopride) group.n=6 in each group. The vasodilatation effects of zacopride on KCl (60 mmol/L) and U46619 (10-6 mol/L) pre-constricted arterial ring were recorded; the effects of different agents on zacopride caused vasodilatation were studied. Results: In both +Endo (zacopride) and –Endo (zacopride) groups, zacopride showed a dose dependent vasodilatation effect on coronary ring pre-constricted by KCl and U46619. The maximum vasodilatation effect of zacopride in KCl treated+Endo (zacopride) group was (90.15 ± 6.38) %, in U46619 treated-Endo (zacopride) group was (81.67 ± 4.97 ) %; the maximum vasodilatation effect of zacopride in KCl treated-Endo (zacopride) group was (85.48±5.04) %, in U46619 treated–Endo (zacopride) group was (79.65 ± 3.51) %, compared to each corresponding vehicle group, allP0.05. Conclusion: Zacopride had vasodilatation effect on coronary arterial ring which was pre-constricted by KCl and U46619, which might be related to the channel of IK1.
ABSTRACT
Inwardly rectifying potassium (Kir) channels are widely distributed in many tissues and play important roles in physiological processes such as maintaining K+ homeostasis, regulating cell excitability and insulin secretion. The activity of Kir channels is regulated by a number of modulators,such as K+, Mg2+, pH, ATP, GPCR, PIP2, PKA, PKC, AA (arachidonic acid), etc. Study of the regulating mechanisms of Kir channel is a key step in understanding the physiology and physiopathology of these channels. Because many extra molecular signals regulate Kir channels via PKC pathway, much effort has been made over the past decade to understand role of PKC in regulating Kir channels. This paper summarizes the molecular basis of PKC modulation of Kir channels and the recent progression on the area.