| Part I The effects of different concentrations of central serotonin on hypoglossal nerve discharge activity in Chronic Intermittent Hypoxia rats.Objective To investigate the effects of different concentrations of serotonin(5-HT)in Hypoglossal motor nuclei(HMN)on hypoglossal discharge activity in Chronic Intermittent Hypoxia rats.Methods Adult male Sprague-Dawley rats were randoml divided into normoxia group and chronic intermittent hypoxia(CIH)group.Normoxia group was further divided into normoxic control group and saline group,CIH group was then divided into Time Control group,5-HT 1mM group,5-HT 10mM group and 5-HT 100mM group.The rats in the normoxic group were placed in the normal pressure oxygen animal rearing cabins,and the CIH group was placed in the animal cabins of normal pressure and intermittent hypoxic condition for 4 consecutive weeks,8h/d,followed by an acute intermittent hypoxia(AIH)stimulation,a 3 times of hypoxia conduction that sustained 5min per time.After microinjection of different reagents into HMN by stereotaxic apparatus,record the changes of hypoglossal nerve discharge.Results(1)There were no significant differences in the hypoglossal nerve discharge amplitude and frequency between the control group and the saline group.(2)At the time of 15min,30min,45min and 60min,the amplitude and frequency of hypoglossal nerve discharge in Time Control group was higher than that of the normoxia control group,the difference was statistically significant(P<0.001).(3)At the time of 15min,30min,45min and 60min,hypoglossal nerve discharge amplitude in 5-HT(1mM)group,5-HT(lOmM)group and 5-HT(100mM)group successively increased.Among them,the hypoglossal nerve discharge amplitudes in 5-HT(lOmM)and 5-HT(100mM)group rats were significantly higher than that of Time group Control and 5-HT(1mM)group(P<0.05),while there was no significant difference between Time Control group and 5-HT(1mM)group.The amplitude of hypoglossal nerve discharge was higher in 5-HT(100mM)group than that of 5-HT(lOmM)group,but only at 15min and 30min(P<0.05).There was no significant difference in the frequency of hypoglossal nerve discharge between CIH groups.Conclusions Conducting CIH in rats for 4 weeks can induce long-term facilitation(LTF)of hypoglossal nerve,and the increased concentration of 5-HT in HMN can enhance the hypoglossal nerve LTF.Part II The effects of sex hormones concentration variation on hypoglossal nerve discharge activity in Chronic Intermittent Hypoxia rats.Objective To investigate the effects of sex hormones concentration variation on hypoglossal nerve discharge activity in Chronic Intermittent Hypoxia rats.Methods 4 weeks old female Sprague-Dawley rats were randomly divided into normoxia group and CIH group,normoxia group was further divided into normal group and sham operation group(SO),CIH group was then divided into control group,ovariectomized group(OVX)and ovariectomy + estrogen group(OVX+E2).4 week old male Sprague-Dawley rats were randomly divided into normoxia group and CIH group,normoxia group was then divided into normal group and sham operation group(SO),CIH group was further divided into control group,gonadectomized group(GDX),gonadectomy + testosterone group(GDX+T)and gonadectomy + testosterone+ aromatase inhibitor group(GDX+T+AI).Normoxia group rats were placed in the normal pressure oxygen animal rearing cabins,rats in CIH group were placed in the animal cabins of normal pressure and intermittent hypoxic condition for 4 consecutive weeks,8h/d,followed by an AIH stimulation,a 3 times of hypoxia conduction that sustained 5min per time.Whereafter,The changes of hypoglossal nerve discharge in each group were recorded and serum sex hormone concentrations were measured.Results The point of estradiol:(1)There was no significant difference in serum estradiol concentration between normoxic normal group(991.02 ± 67.91 pg/ml)and sham operation group(982.97 + 89.10 pg/ml).The serum estradiol concentrations between the normoxic group and the CIH control group(898.61 ± 65.51 pg/ml)had no statistical difference.The serum estradiol concentration in OVX group(339.48 +39.17 pg/ml)decreased significantly(P<0.001)compared with the control group,while there existed no significant difference between OVX+E2 group(921.01 ± 42.76 pg/ml)and control group.(2)At 15min,30min,45min and 60min,the amplitude of hypoglossal nerve discharge in OVX group was lower than that in control group(P<0.001).The discharge amplitude of hypoglossal nerve in OVX+E2 group was significantly lower than that of control group(P<0.05)at 60min,while there existed no significant difference in 15min,30min and 45min.In the OVX group,the discharge frequency of hypoglossal nerve was significantly lower than that of the control group(P<0.05).There was no significant difference between the OVX+E2 group and the control group.(3)The concentration of serum estradiol in female rats was positively correlated with the magnitude of hypoglossal nerve LTF(r=0.955,P<0.001).The point of testosterone:(1)There was no significant difference in serum testosterone concentrations between the normoxic normal group(11.45 ± 0.96 ng/ml)and sham operation group(12.02 ± 1.17 ng/ml).The serum testosterone concentration was significantly lower in the CIH control group(9.81 ± 1.43 ng/ml)than that in the normoxia normal group(P<0.05).The serum testosterone concentration in GDX group(1.76±0.65 ng/ml)decreased significantly(P<0.001)compared with the control group,while there were no statistical differences in GDX+T group(10.17 ± 1.29 ng/ml)and GDX+T+AI group(9.78 ±1.43 ng/ml)compared to the control group.(2)At 15min,30min,45min and 60min,the hypoglossal nerve discharge amplitudes in GDX group and the GDX+T+AI group were less than the control group(P<0.001).There was no significant difference between the GDX+T group and the control group in the hypoglossal nerve discharge amplitude at 15min,30min.At 45min and 60min,the discharge amplitude of hypoglossal nerve in the GDX+T group was significantly lower than that in the control group(P<0.05),and that in GDX group and GDX+T+AI group were significantly lower than GDX+T group(P<0.001).There was statistical difference between the GDX group and the GDX+T+AI group in hypoglossal nerve discharge amplitude at 45min and 60min(P<0.05).The discharge frequency of hypoglossal nerve between GDX+T group and the control group did not statistically differed,while that in GDX group and GDX+T+AI group were significantly lower than the control group(P<0.05).(3)The serum testosterone concentration was positively correlated with the magnitude of hypoglossal nerve LTF(r=0.928,P<0.001)apart from GDX+T+AI group.Conclusions(1)Ovariectomy and estradiol supplement can change the concentration of serum estradiol in female rats,and the estradiol concentration is positively correlated with the of hypoglossal nerve amplitude LTF.(2)Gonadectomy and testosterone supplement can change the concentration of serum testosterone.The testosterone concentrations is positively related to the amplitude of hypoglossal nerve LTF,when getting rid of the influence of aromatase. |
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