Effect of prenatal alcohol exposure on rhythmic respiratory discharge activity in medullary slices of neonatal rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effects of prenatal alcohol exposure on rhythmic respiratory discharge activity (RRDA) in the medullary slices of neonatal rats.</p><p><b>METHODS</b>Ten pregnant female SD rats were exposed to 0, 4%, 6%, 8%, and 10% alcohol in drinking water from 1 week before till 3 days after delivery. The medullary slices of the neonatal rats containing the medial region of the nucleus retrofacialis (mNRF) with the hypoglossal nerve rootlets were prepared and perfused with modified Kreb's solution to record RRDA from the hypoglossal nerve rootlets using suction electrodes.</p><p><b>RESULTS</b>No significant difference was found in RRDA in 50 min among the neonatal rats with prenatal exposure to 0, 4%, 6%, and 8% alcohol, but the RRDA in 10% alcohol exposure group became irregular. Prenatal exposure to increased alcohol concentrations caused attenuated RRDA attenuated in the neonatal rats, shown by shortened inspiratory time (TI), decreased respiratory frequency (RF), and reduced integral amplitude (IA) as compared with those in the control group.</p><p><b>CONCLUSION</b>Prenatal alcohol exposure inhibits RRDA in medullary slices of neonatal rats, which might be a mechanism by which maternal alcohol exposure causes suppressed offspring respiratory functions.</p>

Histamine H1 receptors modulate the discharge activities of inspiratory neurons in the medial region of neonatal rat nucleus retrofacialis ex vivo / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the role of histamine H1 receptors in modulating the discharge activities of the inspiratory neurons in the nucleus retrofacialis of neonatal rats.</p><p><b>METHODS</b>Brainstem slices were obtained from neonatal rats containing the medial region of the nucleus retrofacialis (mNRF) with the hypoglossal nerve (XII nerve) rootlets retained. The rhythmic discharges of the inspiratory neurons (I neurons) and activities of the XII nerve rootlets were simultaneously recorded using microelectrodes and suction electrodes, respectively. The role of H1 receptors in modulation of the discharge activities of the inspiratory neurons was investigated using the H1 receptor agonist histamine and its specific antagonist pyrilamine dissolved in modified Kreb's solution for slice perfusion.</p><p><b>RESULTS</b>Histamine shortened the respiratory cycle (RC) and expiratory time (TE) of the neurons in the brain slices, and pyrilamine produced the opposite effects. Neither histamine nor pyrilamine affected the inspiratory time (TI), integral amplitude (IA) or the peak discharge frequency (PF) of the I neurons.</p><p><b>CONCLUSION</b>H1 receptors play an excitatory role in the modulation of the discharge activities of the inspiratory neurons in neonatal rat brainstem slices.</p>

Glycine is involved in the modulation of respiratory rhythmical discharge activity in neonatal rat medullary brain slices / 南方医科大学学报

<p><b>OBJECTIVE</b>To determine the role of glycine (Gly) in the generation and modulation of basic respiratory rhythm.</p><p><b>METHODS</b>Neonatal (0-3 days) SD rats of either sex were used in this study. The medulla oblongata brain slice containing the medial region of the nucleus retrofacialis (mNRF) and the hypoglossal nerve rootlets was prepared, and the surgical procedure was performed in the modified Kreb's solution (MKS) with continuous carbogen (95% O(2) and 5% CO(2)) within 3 min. The rhythmical respiratory discharge activity (RRDA) of the hypoglossal nerve rootlets was recorded using suction electrode. Eighteen medulla oblongata slice preparations were divided into 3 groups and treated for 20 min with Gly receptor specific agonist Gly (10 micromol/L), Gly receptor antagonist strychnine (STR, 1 micromol/L), or Gly+STR after a 20 min Gly application. The changes in RRDA of the hypoglossal nerve rootlets were observed.</p><p><b>RESULTS</b>Gly significantly decreased the inspiratory time and integral amplitude (IA), but the changes of respiratory cycle (RC) and expiratory time (TE) were not statistically significant. STR induced a decrease in expiratory time and respiratory cycle without significantly affecting the inspiratory time or integral amplitud. The effect of Gly on the respiratory rhythm was partially reversed by additional application of STR.</p><p><b>CONCLUSION</b>Gly may play an important role in the modulation of RRDA in the medulla oblongata slice of neonatal rats.</p>

Role of 5-HT(2A) receptor in increase in respiratory-related rhythmic discharge activity by nikethamide in neonatal rat transverse medullary slices / 生理学报

To investigate the effects of nikethamide on the generation and modulation of rhythmic respiration of neonatal rats and the role of 5-HT(2A) receptor in this course, experiments were performed on the transverse medullary slices of neonatal rats (both sexes, 1-3 d) in vitro. The slices containing the medial region of the nucleus retrofacialis (mNRF) with the hypoglossal nerve rootlets were prepared in which the respiratory-related rhythmic discharge activity (RRDA) was recorded from the hypoglossal nerve rootlets by suction electrode. The possible role of nikethamide on RRDA was investigated by administration of an agonist of 5-HT(2A) receptor, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), and an antagonist of 5-HT(2A) receptor, ketanserine, dissolved in modified Krebos solution (MKS). Thirty slices were randomly divided into five groups: Group 1: the slices were perfused with different concentrations of nikethamide (0.5, 1, 3, 5, 7, 10 μg/mL), and the most effective concentration was selected; Group 2: the slices were perfused with DOI (40 μmol/L); Group 3: the slices were perfused with ketanserine (40 μmol/L); Group 4: the slices were perfused with ketanserine + DOI; Group 5: the slices were perfused with nikethamide, then perfused with nikethamide + ketanserine after washout of nikethamide. Nikethamide increased RRDA in transverse medullary slices at 0.5-7 μg/mL, and 5 μg/mL was the most effective concentration. DOI increased RRDA with prolonged inspiratory time (TI), increased integral amplitude (IA), and shortened respiratory cycle (RC). Ketanserine decreased RRDA with shortened TI, decreased IA and prolonged RC. Ketanserine + DOI had no significant effects on RRDA. The effects of nikethamide on RC and IA were totally and partially reversed by additional application of ketanserine, but the effect of nikethamide on TI was not influenced by ketanserine. It is proposed that nikethamide increases RRDA partly via 5-HT(2A) receptors.

Role of histamine H(1) and H(2) receptors in the modulation of respiratory rhythmical discharge in medulla oblongata slice preparation of neonatal rats / 生理学报

The present study was carried out to determine the role of histamine H(1) and H(2) receptors in the generation of basic respiratory rhythm. Neonatal (aged 0-3 d) Sprague-Dawley rats of either sex were used. The medulla oblongata slice containing the medial region of the nucleus retrofacialis (mNRF) and the hypoglossal nerve rootlets was prepared and the surgical procedure was performed in the modified Kreb's solution (MKS) with continuous carbogen (95% O(2) and 5% CO(2)), and ended in 3 min. Respiratory rhythmical discharge activity (RRDA) of the rootlets of hypoglossal nerve was recorded by suction electrode. Thirty medulla oblongata slice preparations were divided into 5 groups. In groups I, II and III, histamine (5 μmol/L), H(1) receptor specific antagonist pyrilamine (10 μmol/L) and H(2) receptor specific antagonist cimetidine (5 μmol/L) was added into the perfusion solution for 15 min separately. In group IV, after application of histamine for 15 min, additional pyrilamine was added into the perfusion for another 15 min. In group V, after application of histamine for 15 min, additional cimetidine was added into the perfusion for another 15 min. The discharges of the roots of hypoglossal nerve were recorded. Signals were amplified and band-pass filtered (100-3.3 kHz). Data were sampled (1-10 kHz) and stored in the computer via BL-420 biological signal processing system. Our results showed that histamine significantly decreased the respiratory cycle (RC) and expiratory time (TE), but changes of integral amplitude (IA) and inspiratory time (TI) were not statistically significant. Pyrilamine induced significant increases in RC and TE, but changes of TI and IA were not statistically significant. Cimetidine had no effects on RC, TE, TI and IA of RRDA. The effect of histamine on the respiratory rhythm was reversed by additional application of pyrilamine but not cimetidine. Taken together, with the results mentioned above, histamine H(1) receptors but not H(2) receptors may play an important role in the modulation of RRDA in the medulla oblongata slice preparation of neonatal rats.

GABA A receptor participates in respiratory enhancement induced by nikethamide in neonatal rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the role of GABA A receptor in nikethamide-induced respiratory enhancement in the medullary slices of neonatal rats.</p><p><b>METHODS</b>Ex vivo medullary slices of neonatal rats (1 to 3 days old) containing the medial region of the nucleus retrofacialis with the hypoglossal nerve rootlets were prepared and perfused with modified Kreb's solution to record respiration-related rhythmic discharge activity (RRDA) from the hypoglossal nerve rootlets using suction electrodes. Thirty RRDA-positive slices were randomized into 5 equal groups and perfused with nikethamide (at concentrations of 0.5, 1, 3, 5, 7, and 10 microg/ml with the optimal nikethamide concentration determined), GABA (at 10, 20, 40, and 60 micromol/ to determine the optimal concentration), 10 micromol/ bicuculline, 10 micromol/ bicuculline plus 40 micromol/L GABA, and 5 microg/ml nikethamide followed by 5 microg/ml nikethamide plus 10 micromol/ bicuculline after wash out, respectively.</p><p><b>RESULTS</b>Nikethamide increased RRDA at the concentrations of 0.5-7 microg/ml, and 5 microg/ml nikethamide showed the most distinct effect on the inspiratory time (TI), integral amplitude (IA), and respiratory cycle (RC). GABA at 40 micromol/ showed the most effective inhibition of RRDA in terms of TI, IA, and RC. Bicuculline at 10 micromol/ could increase the IA, TI and RC, but the combination of 10 micromol/ bicuculline and 40 micromol/ GABA had no significant effects on RRDA. Compared with nikethamide used alone, nikethamide plus bicuculline significantly increased TI and IA without affecting RC.</p><p><b>CONCLUSION</b>Nikethamide can enhance RRDA of the hypoglossal nerve rootlets in the medullary slices of neonatal rats, and the effect can be partially mediated by the GABA A receptor.</p>

Modulatory Effect of 5-Hydroxytryptamine 2A Receptor on Discharge Activities of Inspiratory Neurons in the Medial Region of Nucleus Retrofacialis of Neonatal Rats in Vitro / 实用儿科临床杂志

Objective To explore the modulatory effect of 5-HT2A receptors on the discharge activities of inspiratory neurons in medial region of nucleus retrofacialis of neonatal rats. Methods Experiments were performed in vitro brainstem slice preparations from neonatal rats. These preparations included the medial region of nucleus retrofacialis with the hypoglossal nerve rootlets retained. The rhythmic discharges of the inspiratory neurons and activities of the hypoglossal nerve rootlets were simultaneously recorded by using microelectrodes and suction electrodes, respectively. Roles of 5-HT2A receptors in modulation of the discharge activities of inspiratory neurons were investigated by administration of the 5-HT2A receptor agonist 1-(2,5-dimethoxy-4-iodopbenyl)-2-aminopropane (DOI), and its specific antagonist ketanserine dissolved in modified Kreb's solution for perfused slices. Results In DOI group, the inspiratory time (TI) was (0.864±0.07)s, expiratory time (TE) was (10.78±1.06)s, respiratory cycle (RC) was (11.79±1.64)s, integral amplitude (IA) was (357.98±37.21)(μV·s) and the peak discharge frequency (PF) was (37.83±3.66)Hz. In control group, they were (0.68±0.06)s, (13.89±2.14)s, (14.77±1.92)s, (273.57±24.39)(μV·s), and (29.92±4.50)Hz, there were significant differences between the 2 groups (Pa<0.01). In ketanserine group, TI was (0.55±0.07)s, TE and RC were (18.43±3.28)s and (20.17+2.91)s respectively, IA and PF were (214.37±33.52)(μV·s) and (22.17±3.92)Hz, there were significant differences between ketanserine group and DOI, control group (Pa<0.01). Conclusion 5-HT2A receptors take part in modulate the discharge activities of inspiratory neurons in neonatal rat brainstem slices.

Expression of c-fos Protein in Hippocampus of Newborn Rats with Hypoxic-Ischemic Brain Damage and Its Significance / 实用儿科临床杂志

Objective To explore the relationship of c-fos protein and cell apoptosis by observing the expression of c-fos protein in hippocampus of newborn rat with hypoxic-ischemic brain damage(HIBD).Methods Forty-eight 7-day SD neonatal rats were randomly divided into control group(n=6) and experiment group(n=42).The models of HIBD were established in neonatal rats by inhaling the mixed gases of 920 mL/L N2 and 80 mL/L O2,and the animals were sacrificed by dislocation their heads at different time points(0.5,1,3,6,12,24,48,72 h),then the hippocampus were dissected by morphological analysis.Results The apoptotic cells appeared at the time point of 3 h,and reached the peak at 48 h,then decreased.The positive cell of c-fos protein increased from the time point of 30 min and reached the peak at 2 h and then decreased gradually,and there was a contrary tendency between the expression of c-fos protein and the number of damaged brain cells by HIBD(r=-0.57 P

Modulatine Role of Gamma-Aminobutyric Acid A Receptor on Respiratory Rhythmical Discharge Activity in Brainstem Slice of Neonatal Rat / 实用儿科临床杂志

Objective To explore the modulation roles of gamma-aminobutyric acid A(GABAA) receptor on respiratory rhythmical discharge activity in brainstem slice of neonatal rats.Methods Experiments were performed on in vitro neonatal rats brainstem slices.The slices containing the medial region of the nucleus retrofacialis(mNRF)with the hypoglossal nerve rootlets retained was prepared in which the respira-tory-related rhythmic discharge activity(RRDA)were recorded from hypoglossal nerve rootlets by suction electrode.The possible role of GABAA receptor on RRDA was investigated by administration of GABA and its antagonist bicuculline in modified Kreb′s solution(MKS),for perfusion of the brainstem slices.Eighteen slices positive of RRDA were randomly divided into three equal groups:the first group of slices was perfused with different concentrations(10,20,40,60 ?mol/L) GABA and the most effective concentration was selected;the second group of slices was perfused with 10 ?mol/L bicuculline;the third group of slices was perfused with 10 ?mol/L bicuculline plus 40 ?mol/L GABA.The RRDA in 3 groups were observed.Results GABA decreased RRDA,40 ?mol/L was the most effective concentration.It shortened inspiratory time(TI),decreased integral amplitude(IA),prolonged respiratory cycle(RC) and expiratory time(TE) respectively.By contrast,10 ?mol/L bicuculline produced opposite effects on RRDA,it prolonged TI,increased IA,shortened RC and TE respectively.40 ?mol/L GABA plus 10 ?mol/L bicuculline had no significant effects on RRDA.Conclusion GABA plays an important role in modulate RRDA of neonatal rats via GABAA receptor.