Dopamine receptor 1 modulates the discharge activities of inspiratory and biphasic expiratory neurons via cAMP-dependent pathways.

Dopamine receptor 1 (D(1)R) plays an essential role in regulating respiratory activity in mammals, however, little is known about how this receptor acts to modulate the basic respiratory rhythmogenesis. Here, by simultaneously recording the discharge activities of biphasic expiratory (biphasic E) neurons/inspiratory (I) neurons and the XII nerve rootlets from brainstem slices, we found that the application of D(1)R agonist cis-(±)-1-(aminomethyl)-3,4-dihydro-3-phenyl-1H-2-benzopyran-5,6-diolhydrochloride (A68930, 5 μM), or forskolin, an intracellular cAMP-increasing agent, substantially decreased respiratory cycle and expiratory time of both types of neurons, and elevated the integral amplitude and frequency of XII nerve rootlets discharge. These changes were reversed by subsequent application of their antagonists SCH-23390 and Rp-Adenosine 3',5'-cyclic monophosphorothioate triethylammonium salt hydrate (Rp-cAMPS), respectively.

[Involvement of cAMP-PKA pathway in group Ⅱ metabotropic glutamate receptors-mediated regulation of respiratory rhythm from neonatal rat brainstem slice].

The study aims to identify the role of cAMP-PKA pathway in the group Ⅱ metabotropic glutamate receptors (mGluRs)-mediated regulation of respiratory rhythm from the brainstem slice. Neonatal (aged 0-3 d) Sprague-Dawley rats of either sex were used. The brainstem 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% O2 and 5% CO2) bubbling, and ended in 3 min.

[Group II metabotropic glutamate receptors is involved in the modulation of respiratory rhythmical discharge activity in neonatal rat medullary brain slices].

Objective: To explore the role of group II metabotropic glutamate receptors in the modulation of basic respiratory rhythm.

Methods: Neonatal (0-3 days) SD rats of either sex were used. 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% O2 and 5% CO2) within 3 min.

[Effect of doxapram on the respiratory rhythmical discharge activity in the brainstem slice of neonatal rats].

Objective: To investigate the effects of doxapram on the respiratory rhythmical discharge activity (RRDA) in the brainstem slices of neonatal rats.

Methods: Thirty neonatal SD rats (of either sex, 0-3 days old) were randomly divided into 6 equal groups (groups I-VI), and the brainstem slices which contained the medial region of the nucleus retrofacialis (mNRF) were prepared. All the slices were perfused with modified Kreb's solution (MKS), and in group I (control group), the slices were perfused with MKS only; in groups II to IV, the slices were perfused with doxapram in MKS continuously at the concentrations of 2, 5, and 10 micromol/L, respectively; in groups V and VI, the slices were perfused with 20 micromol/L propofol and 20 micromol/L propofol plus 5 micromol/L doxapram, respectively.

Glial cells are involved in the exciting effects of doxapram on brainstem slices in vitro.

This study tested whether the glial cells are involved in the exciting effects of doxapram on brainstem slice in vitro. Experiments were performed in brainstem slice preparations from neonatal rats. The medial area of nucleus retrofacialis (mNRF) and the hypoglossal nerve (XII nerve) were contained in the preparations.

[Histamine H1 receptors modulate the discharge activities of inspiratory neurons in the medial region of neonatal rat nucleus retrofacialis ex vivo].

Objective: To investigate the role of histamine H1 receptors in modulating the discharge activities of the inspiratory neurons in the nucleus retrofacialis of neonatal rats.

Methods: 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.

[Effects of glycine on the discharge activities of the inspiratory neurons in neonatal rat medulla oblongata slices].

Objective: To observe the effect of glycine on the discharge activities of inspiratory neurons in the medulla oblongata slices of neonatal rats.

Methods: Neonatal rat medulla oblongata slices including the medial region of the nucleus retrofacialis (mNRF) with the hypoglossal nerve rootlets retained were prepared. The activity of the inspiratory neurons in the mNRF and the respiratory rhythmical discharge activity (RRDA) of the hypoglossal nerve rootlets were simultaneously recorded using microelectrodes and suction electrodes, respectively.

[Effect of glial cell metabolism on respiratory rhythmical discharge activity in neonatal rat medulla oblongata slices].

Objective: To explore the role of glial cell metabolism in the generation and regulation of central respiratory rhythm.

Methods: The medulla oblongata slices (600-700 microm) containing the medial region of the nucleus retrofacialis (mNRF) with the hypoglossal nerve rootlets retained from 12 neonatal (0-3 days) Sprague-Dawley rats were prepared and perfused with modified Kreb's solution (MKS). Upon recording of respiratory rhythmical discharge activity (RRDA) of the rootlets of the hypoglossal nerve, the brain slices were treated with glial cell metabolism antagonist L-methionine sulfoximine (L-MSO, 50 micromol/L) for 20 min followed by application of glial cell metabolism agonist L-glutamine (L-GLN, 30 micromol/L) for 20 min, or with L-MSO for 20 min with additional L-GLN for 20 min.

[Identification and classification of respiratory pacemaker neurons in the medial region of nucleus retrofacialis in neonatal rats.].

The aim of the present study is to supply direct experimental proof that the medial region of nucleus retrofacialis (mNRF) is the site generating basic rhythm of respiration. Medullary slices of neonatal Sprague-Dawley rats, including hypoglossal nerve root and mNRF, were made according to Suzue's method. Simultaneous recordings of the respiratory rhythmic discharge activity (RRDA) in hypoglossal nerve root with suction electrode and the respiratory neuronal discharge in the mNRF with whole cell patch clamp were performed on the brainstem slice in vitro.

[Effects of A68930 on rhythmical respiratory discharge in isolated neonatal rat brainstem slice].

Objective: To investigate the role of dopamine-1 receptor in the modulation of basic respiration rhythm.

Methods: Newborn SD rat (0-3 days, n=20) brain stem slices containing the medial region of the nucleus retrofacialis (mNRF) were prepared with the hypoglossal nerve roots retained. The respiratory rhythmical discharge activity (RRDA) of the hypoglossal nerve was recorded using suction electrodes on these preparations, and the effects of dopamine-1 receptor on RRDA were investigated by application of the specific agonist of dopamine-1 receptor A68930 at different concentrations (0, 1, 2, and 5 micromol/L) in the perfusion solution.

[Glycine is involved in the modulation of respiratory rhythmical discharge activity in neonatal rat medullary brain slices].

Objective: To determine the role of glycine (Gly) in the generation and modulation of basic respiratory rhythm.

Methods: 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.

[D(1)-dopamine receptor is involved in the modulation of the respiratory rhythmical discharge activity in the medulla oblongata slice preparation of neonatal rats in vitro.].

To explore the role of D(1)-dopamine receptor in the modulation of basic respiratory rhythm, neonatal (0-3 d) Sprague-Dawley rats of either sex were used. The medulla oblongata slice was prepared and the surgical procedure was performed in the modified Kreb's solution (MKS) with continuous ventilating 95% O2 and 5% CO2 and ended in 3 min. A 600-700 mum single transverse slice containing the hypoglossal nerve roots and some parts of the ventral respiratory group was cut.

[Role of histamine H(1) and H(2) receptors in the modulation of respiratory rhythmical discharge in medulla oblongata slice preparation of neonatal rats].

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.

[Role of 5-HT(2A) receptor in increase in respiratory-related rhythmic discharge activity by nikethamide in neonatal rat transverse medullary slices].

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).

[GABA A receptor participates in respiratory enhancement induced by nikethamide in neonatal rats].

Objective: To investigate the role of GABA A receptor in nikethamide-induced respiratory enhancement in the medullary slices of neonatal rats.

Methods: 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.

[Effects of 8-OH-DPAT on respiratory rhythmical discharge activity in isolated neonatal rat brainstem slice].

Objective: To investigate the role of 5-HT1A receptors in the generation and modulation of basic respiration rhythm.

Methods: Brainstem slices of 20 newborn SD rats (0-3 days) were prepared and respiratory rhythmical discharge activity (RRDA) of the hypoglossal nerve was recorded by suction electrode on these preparations including the medial region of the nucleus retrofacialis (mNRF) with the hypoglossal nerve rootlets retained, and the effects of 5-HT1A receptors on RRDA were investigated by application of specific agonist of 5-HT1A receptors 8-OH-DPAT in the perfusion solution. The 20 neonatal rats were divided into 4 groups and the brainstem slices were perfused continuously for 10 min with different concentrations of 8-OH-DPAT (1, 5, 10, 20 micromol/L, respectively).

[5-HT(1A) receptors are involved in the modulation of respiratory rhythmical discharge activity in the medulla oblongata slice preparation of neonatal rats].

The present study was carried out to determine the role of 5-HT(1A) receptors in the generation and modulation of basic respiratory rhythm. Neonatal (aged 0-3 d) Sprague-Dawley rats of either sex were used. The medulla oblongata slice was prepared and the surgical procedure was performed in the modified Kreb's solution (MKS) with continuous carbogen (95% O2 and 5% CO2), and ended in 3 min.

[Role of 5-HT2A-receptors coupled with superoxide anion in the medial area of nucleus retrofacialis].

Objective: To explore the effect of 5-HT2A-receptors coupled with superoxide anion (O2-) on respiratory regulation signal transductionin passageway in the medial area of nucleus retrofacialis (mNRF).

Methods: mNRF island was prepared from medullary slices of neonatal SD rats according to Johnson's method and transferred separately into 24-well culture plates with reagents according to protocol, followed by incubation for 60 min at 37 degrees C in a humidified incubator with 5% CO2. Absorbance of 100 microl supernatant was measured by spectrophotometry at 550 nm and the effect of 5-HT and 2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI, agonist of 5-HT2A-receptors) on O2- generation in the mNRF was observed, along with the inhibition of this effect by ketanserin (antagonist of 5-HT2A-receptors) and alpha-lipoic acid (alpha-LA, a antioxidant).

[Effects of pentobarbital sodium on rhythmical respiration of neonatal rat medullary preparations].

Objective: To study the effects of pentobarbital sodium in generation and modulation of rhythmical respiration in neonatal rats.

Methods: The effects of pentobarbital sodium were examined on hypoglossal nerve (XII) rootlets and inspiratory neurons in the medullary preparations including the medial region of the nucleus retrofacialis, pre-Bötzinger complex and the dorsal respiratory group of neonatal rats aged 0-3 days. The electrical activity of XII nerve rootlets and inspiratory neurons were recorded.

[Isolation and physiological characterization of mesenteric arterial smooth muscle cells].

Vascular smooth muscle cells (VSMCs) are crucial for studying the mechanism and regulation of vasogenic response, but so far no ideal method has been reported for their isolation. We established a VMSC isolation method based on two-step digestion, with which a large population of single smooth muscle cells could be obtained. After cell isolation, the potassium current, cytosolic calcium concentration, reactivity to caffeine were measured, and the results demonstrated that the cells were highly viable and exhibited reactivity to the vascular constrictor to meet various needs in experimental research.

Adenosine A1 receptors modulate the discharge activities of inspiratory and biphasic expiratory neurons in the medial region of Nucleus Retrofacialis of neonatal rat in vitro.

This study investigated whether adenosine A1 receptors could modulate respiratory rhythm in mammals. Experiments were performed in in vitro brainstem slice preparations from neonatal rats. These preparations included the medial region of Nucleus Retrofacialis (mNRF) with the hypoglossal nerve (XII nerve) rootlets retained.

[Effect of adenosine A1-receptors on the respiratory rhythmical discharge activity in neonatal rat brainstem slice in vitro].

Objective: To explore the role of adenosine A(1)-receptors in the generation and regulation of central respiratory rhythm.

Methods: Neonatal rat brainstem slices including the medial region of the nucleus retrofacialis (mNRF) with the hypoglossal nerve rootlets retained were prepared in which the respiratory activity was recorded from the hypoglossal nerve rootlets by suction electrode. The possible role of adenosine A(1)-receptors on rhythmical respiration was investigated by administration of specific antagonist of adenosine A(1)-receptor R-phenylisopropyl-adenosine (R-PIA) and its antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) in modified Kreb's solution (MKS) for perfusion of the brainstem slices.

Adenosine A1 receptors are involved in the modulation of the rhythmical respiration in neonatal rat brainstem slice in vitro.

This study was designed to investigate whether adenosine A1 receptors could modulate primary rhythmical respiration in mammals. Experiments were performed in in vitro brainstem slice preparations from neonatal rats. These preparations included the medial region of the nucleus retrofacialis (mNRF) with the hypoglossal nerve rootlets retained.

[Nitric oxide is involved in the modulation of central respiratory rhythm].

This experiment was expected to test whether nitric oxide (NO) exerted significant effect on the central respiratory rhythm. Experiments were performed on in vitro brainstem slice preparations from neonatal rats. These preparations include the medial region of the nucleus retrofacialis (mNRF); a part of pre-Bötinger complex, ventral respiratory group (VRG) and dorsal respiratory group (DRG).

[Effect of propofol on the electric discharge of inspiratory neurons in the brainstem of neonatal rats].

Objective: To investigate the effects of propofol on the electric discharge of the inspiratory neurons in the neonatal rat brainstem slices and its possible mechanism.

Methods: Experiments were performed on in vitro neonatal rat (of either sex, 0 to 30 d old) brainstem slices perfused with modified Kreb's solution (MKS), and the rhythmical discharge activity of the inspiratory neurons in the hypoglossal nerve was recorded by suction electrode. Thirty-six slices positive of respiratory-related rhythmic activity were randomly divided into 6 equal groups consisting of a control group (group I) with MKS perfusion, 4 propofol groups (groups II to V) with propofol treatment delivered via continuous MKS perfusion for 3 min at the doses of 5, 20, 50, 100 micromol/L respectively, and a bicuculline-propofol group (group VI) with the continuous perfusion of bicuculline (20 micromol/L) and propofol (20 micromol/L).