| Nitric oxide is involved in the modulation of the basic rhythmical respiration in vitro brainstem slice from neonatalratObject1. This experiment was expected to test whether NO (nitric oxide) exerted significant effects on basic rhythmical respiration.2. To investigate the role of NO in the basic rhythmical respiration generation and modulation by exploring the effects of substrate N donor of NO and inhibitor of nNOS (neuronal nitric oxide synthase) on the discharge activity of inspiratory neurons in mNRFMethods:Experiments were performed on in vitro brainstem slice preparations isolated from neonatal rats (0-3 d). These preparations include the medial region of the nucleus retrofacialis (mNRF); a part of pre-Botinger Complex, ventral respiratory group (VRG) and dorsal respiratory group (DRG).l)Respiratory-related burst activities were recorded from hypoglossal nerve rootlets before and during perfusion of the slice preparation with L-Arg (L-Arginine), SNP(sodium nhroprusside) or 7-NI (7-nitro indazole, an inhibitor of neuronal nitric oxide synthase).2)As monitoring the respiratory-related burst activities of hypoglossal nerve rootlets, we recorded the discharge of inspiratory neurons in the mNRF by inserting the glass microeletrode into the mNRF of the slice. These inspiratory neurons were determined according to the temporal relationship between the neuronal discharge and the hypoglossal nerve activity. Drugswere administered by bath application and their effects on the inspiratoryneuronal activity were investigated.Results:1. Results from experiments on recording respiratory-related burst activities of hypoglossal nerve rootlets. 1) After perfused with different concentrations of L-Arg (500@mol/L~2mmol/L) and SNP (100@mol/L~2mmol/L) , there was no significant change in RRDA; 2) 7-NI, an inhibitor of nNOS, had no effect on the TE, RC,but it decreased the integral amplitude of burst (IA) and inspiratory time (TI), and this kind of inhibition is dose-dependent and time-dependent: during the control perfusion, TI(inspiratory time) is 1.39 ± 0.05s, IA (integral amplitude) is 1387.00 + 65.16@V.ms , at 5min after application of 500@mol/L 7-NI, TI is 1.01±0.05s, IA is 1274.00 ±55.82@Vms (P<0.05), and at lOmin, TI is 0.89±0.05s, IA is 1218.00+55.34uV'ms (P<0.05) . In 1mmol/L 7-NI group, before given the drug, TI is 1.01 ± 0.18s, IA is 1642.83±226.90@V.ms; at 5min after given the drug, TI is 0.87±0.14s, IA is 1528.43±189.02@V.ms (P<0.05); at lOmin, TI is 0.37 + 0.12s, IA is 1278.83+ 180.92uV-ms (PO.05); In 2mmol/L 7-NI group, TI is 1.17+0.06s, IA is 1356.00+65.16uV-ms when perfusion with MKS; at 5min, TI is 0.87±0.05, IA is 1190.00±57.82uV-ms (PO.05); at lOmin, TI is 0.32 +0.03s, IA is 966.00+ 58.34uV'ms (PO.05). As shown above, at lOmin after addition of different concentrations of 7-NI, TI decreased 36%, IA decrease 12% when the concentration of 7-NI is 500umol/L; when the concentration of 7-NI is Immol/L, TI decrease 63%, IA decrease 22%; at 2mmol/L, TI decrease 73 %, IA decrease 28 %. 3) After only given the same concentration of DMSO (dimethyl sulfoxide, DMSO) as dissolving the 7-NI, there is no significant difference between the MKS group and experimental group.2. Result from experiments on recording of discharge of inspiratory neurons in the mNRF: 1) In the MKS group, TI is 0.5811 ± 0.0297s , Fn (average neuronal discharge frequency) is 25.39 ± 5.041Hz; 2) Afergiven L-Arg, SNP respectively, Fn is 26.79 ± 5.11 Hz and 26.43 ± 5.02Hz , TI is 0.5733 ± 0.0253s and 0.5628 ± 0.0265s , there is no significant change compared with the control group (P>0.05) ; 3) After application of 7-NI, TI is 0.1894 ± 0.0247s, Fn is 17.58±4.783Hz, they decrease 67.4% and 30.8% respectively.Conlusion1. NO may take part in the IOS (inspiratory off-switching mechanism because of its regulation to the inspiration.2. NO can regulate the amplitude and frequency of respiration, but the regulation on amplitude of respiratory bursts of NO is more powerf... |
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