The nucleus tractus solitarii (NTS) is one of the morphologically and functionally defined centers that engage in the autonomic regulation of cardiovascular activity. Phenotypically-characterized NTS neurons have been implicated in the differential regulation of blood pressure (BP). Here, we investigated whether phenylethanolamine N-methyltransferase (PNMT)-expressing NTS (NTS^PNMT) neurons contribute to the control of BP. We demonstrate that photostimulation of NTS^PNMT neurons has variable effects on BP. A depressor response was produced during optogenetic stimulation of NTS^PNMT neurons projecting to the paraventricular nucleus of the hypothalamus, lateral parabrachial nucleus, and caudal ventrolateral medulla. Conversely, photostimulation of NTS^PNMT neurons projecting to the rostral ventrolateral medulla produced a robust pressor response and bradycardia. In addition, genetic ablation of both NTS^PNMT neurons and those projecting to the rostral ventrolateral medulla impaired the arterial baroreflex. Overall, we revealed the neuronal phenotype- and circuit-specific mechanisms underlying the contribution of NTS^PNMT neurons to the regulation of BP.
Solitary Nucleus/metabolism* ; Blood Pressure/physiology* ; Phenylethanolamine N-Methyltransferase/metabolism* ; Neurons/metabolism* ; Paraventricular Hypothalamic Nucleus/metabolism*

Animals ; Gallbladder ; physiology ; Rabbits ; Solitary Nucleus ; drug effects ; Thyrotropin-Releasing Hormone ; pharmacology ; Vagus Nerve ; drug effects ; physiology

OBJECTIVETo probe into the bidirectional regulation of acupuncture in the rat with motility abnormality of the stomach and the nerve mechanism.

METHODSAdopting electrophysiological methods, the extracellular discharge signals of neuronic action in NTS were recorded with glass microelectrodes. The effects of acupuncture at "Zusanli" (ST 36), "Neiguan" (PC 6), "Zhongwan" (CV 12), "Qihai" (CV 6) on discharges of NTS neurons and intra-gastric pressure were observed in the rat at normal physiological state, and increase or reduction of gastric motility.

RESULTSAcupuncture at "Zusanli" (ST 36), "Neiguan" (PC 6) could significantly promote gastric motility of the rat at normal status, increase or reduction of gastric motion, while acupuncture at "Zhongwan" (CV 12), "Qihai" (CV 6) could significantly inhibit gastric motion. And acupuncture at all the above acupoints could activate discharges of NTS neurons.

CONCLUSIONThe bidirectional regulation effect of an acupoint does not certainly indicate that the same point has bidirectional regulation effect on an internal organs at different pathological states, while this may show synthetic action of different points which is a good regulation towards normal states and homeostasis.

Acupuncture Points ; Acupuncture Therapy ; Animals ; Gastrointestinal Motility ; Male ; Rats ; Rats, Sprague-Dawley ; Solitary Nucleus ; physiology ; Stomach Diseases ; physiopathology ; therapy

OBJECTIVETo investigate the central mechanism of hypoglycemic effect induced by ear acupuncture.

METHODSExtracellular single-unit recordings were carried out in nucleus tractus solitarius (NTS) of rats after infusion of glucose, insulin via jugular venous and electroacupuncture at auricular concha, observing responses of glucose-sensitive neurons and insulin-sensitive neurons in NTS to electroacupuncture stimulation at auricular concha.

RESULTSThere existed glucose-sensitive neurons and insulin-sensitive neurons in NTS. Among glucose-sensitive neurons, inhibitory ones accounted for 37.3%, and excitable ones accounted for 10.9%. Among the insulin-sensitive neurons, excitable ones accounted for 33.3%, and inhibitory ones accounted for 4.9%. When electroacupuncture was given at auricular concha, 49.3% (34/69) of total neurons recorded in NTS showed increase in firing rate, while 4.3% (3/69) showed decrease in firing rate. Among the 34 exciting-responsive neurons, there were 18 neurons responding to glucose infusion with a discharge decreased in frequency, and there were 8 neurons responding to insulin infusion with a discharge increased in firing rate.

CONCLUSIONAcupuncture stimulation at auricular concha can irritate the neurons in NTS, which show largely inhibitory and excitable response to glucose and insulin infusion, respectively. The hypoglycemic effect induced by auricular acupuncture possibly results from regulating these neurons' firing activities.

Acupuncture, Ear ; Animals ; Electroacupuncture ; Glucose ; pharmacology ; Insulin ; pharmacology ; Male ; Rats ; Rats, Sprague-Dawley ; Solitary Nucleus ; drug effects ; physiology

The autonomic nervous system (ANS) integrates the function of the internal organs for the homeostasis against various external environmental changes. The efferent components of the ANS are regulated by sensory signals arising from the viscera as well as non-visceral organs. The central neural networks that integrate these sensory signals and modify visceral motor output are complex, and synaptic reflexes formed in the brainstem and spinal cord integrate behavioral responses and visceral responses through the central neural networks. A detailed understanding of the neural network presented above may explain the role of the vestibular system on the homeostasis more extensively.
Autonomic Nervous System ; Brain Stem ; Homeostasis ; Physiology ; Reflex ; Solitary Nucleus ; Spinal Cord ; Spinal Cord Lateral Horn ; Viscera

The aim of the present study was to observe whether protein tyrosine kinase (PTK) within the nucleus tractus solitarius (NTS) was involved in the regulation of ventilatory responses of peripheral chemoreflex. The experiments were performed on anesthetized, immobilized and artificially ventilated rabbits. Peripheral chemoreflex was elicited by ventilating the animal with 10% O2-balance 90% N2. Changes in the peak amplitude and frequency of integrated phrenic nerve activity were observed. The ventilatory responses of peripheral chemoreflex following 0.1 microl microinjection within the NTS of either PTK inhibitor genistein (10 mol/L), AMPA glutamate receptor inhibitor CNQX (10 mol/L),or inactive PTK inhibitor daidzein (10 mol/L) were recorded. The results are as follows: Both genistein and CNQX attenuated the ventilatory responses of peripheral chemoreflex, while no changes occurred following daidzein. The amplitude of integrated phrenic nerve discharge and the phrenic burst frequency were decreased by (-21.77+/-6.93)% and (-24.70+/-7.61)% respectively after administration of genistein. CNQX resulted in similar decreases in the amplitude of phrenic nerve discharge (-27.13+/-7.63)% and the burst frequency (-21.34+/-4.88)%. In addition, the inhibitory effects of CNQX and genistein were the same whether they were applied alone or one after another, indicating that they had no cooperative effects. The results obtained suggest that PTK within the NTS regulates the peripheral chemoreflex control of respiration and that this regulation of PTK may be mediated through the phosphorylation of AMPA receptors in NTS neurons.
Animals ; Brain Stem ; enzymology ; physiology ; Chemoreceptor Cells ; physiology ; Female ; Male ; Protein-Tyrosine Kinases ; physiology ; Rabbits ; Receptors, AMPA ; physiology ; Respiration ; Solitary Nucleus ; enzymology

The carotid sinus baroreceptor reflex (CSR) is an important approach for regulating arterial blood pressure homeostasis instantaneously and physiologically. Activation of the central histaminergic or cholinergic systems results in CSR functional inhibitory resetting. However, it is unclear whether two systems at the nucleus tractus solitarius (NTS) level display cross interaction to regulate the CSR or not. In the present study, the left or right carotid sinus region was isolated from the systemic circulation in Sprague-Dawley rats (sinus nerve was reserved) anesthetized with pentobarbital sodium. Respective intubation was conducted into one side isolated carotid sinus and into the femoral artery for recording the intracarotid sinus pressure (ISP) and mean arterial pressure (MAP) simultaneously with pressure transducers connection in vivo. ISP was set at the level of 0 mmHg to eliminate the effect of initial internal pressure of the carotid sinus on the CSR function. To trigger CSR, the ISP was quickly elevated from 0 mmHg to 280 mmHg in a stepwise manner (40 mmHg) which was added at every step for over 4 s, and then ISP returned to 0 mmHg in similar steps. The original data of ISP and corresponding MAP were fitted to a modified logistic equation with five parameters to obtain the ISP-MAP, ISP-Gain relationship curves and the CSR characteristic parameters, which were statistically compared and analyzed separately. Under the precondition of no influence on the basic levels of the artery blood pressure, the effects and potential regulatory mechanism of preceding microinjection with different cholinoceptor antagonists, the selective cholinergic M1 receptor antagonist, i.e., pirenzepine (PRZ), the M2 receptor antagonist, i.e., methoctramine (MTR) or the N1 receptor antagonist, i.e., hexamethonium (HEX) into the NTS on the changes in function of CSR induced by intracerebroventricular injection (i.c.v.) of histamine (HA) in rats were observed. Meanwhile, the actions and possible modulatory mechanism of preceding microinjection with different histaminergic receptor antagonists, the selective histaminergic H1 receptor antagonist, i.e., chlorpheniramine (CHL) or the H2 receptor antagonist, i.e., cimetidine (CIM) into the NTS on the changes in function of CSR resulted from the i.c.v. cholinesterase inhibitor, physostigmine (PHY) were also examined in order to confirm and to analyze effects of cross interaction between central histaminergic and cholinergic systems on CSR. The main results obtained are as follows. (1) Standalone microinjection of different selective cholinergic receptor antagonists (PRZ, MTR or HEX) or different selective histaminergic receptor antagonists (CHL or CIM) into the NTS with each given dose had no effects on the CSR function and on the basic levels of the artery blood pressure, respectively (P > 0.05). (2) The pretreatment of PRZ or MTR into the NTS with each corresponding dose could attenuate CSR resetting resulted from i.c.v. HA in some degrees, which remarkably moved the posterior half range of ISP-MAP relationship curve downwards (P < 0.05), shifted the middle part of ISP-Gain relationship curve upwards (P < 0.05), and increased reflex parameters such as the MAP range and maximum gain (P < 0.05), but decreased parameters such as saturation pressure and intracarotid sinus pressure at maximum gain (P < 0.05). The catabatic effects of pretreatment with MTR into the NTS on CSR resetting induced by i.c.v. HA were more obvious than those with PRZ (P < 0.05), but pretreatment of HEX with given dose into the NTS had no effects on CSR resetting induced by i.c.v. HA (P > 0.05). (3) The effects of pretreatment of CHL or CIM into the NTS with each corresponding dose on CSR resetting made by i.c.v. PHY were similar to those of pretreatment of PRZ or MTR into the NTS on CSR resetting resulted from i.c.v. HA, and the decreasing effects of pretreatment with CHL into the NTS on CSR resetting induced by i.c.v. PHY were more remarkable than those with CIM (P < 0.05). These findings suggest that CSR resetting resulted from either HA or PHY into the lateral ventricle may partly involve the descending histaminergic or cholinergic pathway from the hypothalamus to NTS, which might evoke a cross activation of the cholinergic system in the NTS, via cholinergic M1 and M2 receptors mediation, especially the M2 receptors showing actions, or trigger another cross activation of the histaminergic system in the NTS, by histaminergic H1 and H2 receptors mediation, especially the H1 receptors displaying effects.
Animals ; Baroreflex ; Carotid Sinus ; physiology ; Chlorpheniramine ; pharmacology ; Cholinergic Antagonists ; pharmacology ; Cimetidine ; pharmacology ; Histamine ; pharmacology ; Pressoreceptors ; physiology ; Rats ; Rats, Sprague-Dawley ; Solitary Nucleus ; physiology

OBJECTIVETo explore the role of area postrema (AP) of medulla in control of cardiovascular functions in rat.

METHODS(1) Sprague Dawley rats were anaesthetized with urethane and pentobarbital and the AP was stimulated by electrical stimulus with intensity of 0.1 mA and frequencies ranged 10 approximate, equals 80 Hz. (2) Excitatory amino acid L-glutamate (L- Glu, 0.1 approximate, equals 0.5 mol/L) was microinjected into AP in urethane anaesthetized rats and the changes of mean arterial pressure (MAP) and heart rate (HR) were recorded.

RESULT(1) When the frequencies of 10 Hz, 20 Hz and 40 Hz were used, the electrical stimulation of AP caused decrease of MAP and HR (P<0.001),while the electrical stimulation with the frequencies of 60 Hz and 80 Hz caused an increase of MAP (P<0.05) but a decrease of HR (P<0.001). (2) Microinjection of L-Glu at 0.1 mol/L had no effect on MAP and HR (P>0.05), but it decreased MAP and HR at 0.15 mol/L (P<0.001, P<0.05). The MAP was increased (P<0.001) but HR (P<0.05) was decreased at the concentrations of 0.2 mol/L and 0.5 mol/L, respectively.

CONCLUSIONAlterations of MAP and HR induced by electrical or chemical stimulation on AP of medulla are related to the frequency of electrical stimulation or concentration of L-Glu.

Animals ; Area Postrema ; physiology ; Blood Pressure ; drug effects ; Electric Stimulation ; Glutamic Acid ; pharmacology ; Heart Rate ; drug effects ; Male ; Rats ; Rats, Sprague-Dawley ; Solitary Nucleus ; physiology

AIMTo investigate the roles of alpha1 and alpha2 receptors in the nucleus tractus solitarius (NTS) in the carotid baroreflex (CBR) resetting induced by the intracerebroventricular injection (ICV) of histamine (HA).

METHODSThe left and right carotid sinus regions were isolated from the systemic circulation in 25 Sprague-Dawley rats anesthetized with pentobarbital sodium. The intracarotid sinus pressure (ISP) was altered in a stepwise manner. ISP-mean arterial pressure (MAP) relationship curve and its characteristic parameters were constructed by fitting to the logistic function with five parameters. The changes in CBR performance induced by ICV HA and the effects of pretreatment with alpha1 or alpha2 receptor antagonist into the NTS on the responses of CBR to HA were examined.

RESULTSICV HA (60 micromol x L(-1) in 5 microl) significantly shifted the ISP-MAP relationship curve upwards (P < 0.05) and moved the middle part of ISP-Gain relationship curve downwards (P < 0.05), and reduced the MAP range and maximum gain (P < 0.05). The pretreatment with phenoxybenzamine (PBZ, a selective antagonist of alpha1 receptor, 3 micromol x L(-1) in 500 nl) or yohimbine (YOH, a selective antagonist of alpha2 receptor, 2.5 micromol x L(-1) in 500 nl) into the NTS could obviously intensify the above-mentioned changes in CBR performance induced by HA, but the intensive effect of PBZ was less remarkable than that of YOH (P < 0.05).

CONCLUSIONThe intracerebroventricular administration of HA results in a rapid resetting of CBR and a decrease in reflex sensitivity, and the functions of alpha1 and alpha2 receptors in the NTS might weaken CBR resetting induced by ICV HA. Furthermore, alpha2 receptor in the NTS might play an more important role in modulating the responses of CHR to HA.

Animals ; Baroreflex ; drug effects ; Blood Pressure ; Carotid Sinus ; drug effects ; Histamine ; administration & dosage ; pharmacology ; Injections, Intraventricular ; Male ; Rats ; Rats, Sprague-Dawley ; Solitary Nucleus ; drug effects ; physiology

This experiment aimed to investigate the effect of adrenergic system in the subnucleus commissuriu of nucleus solitrius tractus (CNTS) on renal nerve discharges. Norepinephrine (NE) was microinjected into the CNTS of rabbits and mean arterial blood pressure (MAP) and renal nerve discharges (FRND) were synchronously recorded. The results indicated that (1) microinjection of norepinephine into the CNTS of rabbit could significantly attenuate the frequency of renal nerve discharge, and at the same time decrease markedly the mean arterial pressure. (2) Microinjection of 0.3 nmol yohimbin into CNTS had no significant influence on FRND and MAP, but could attenuate and even reverse the effects of NE on FRND and MAP. These results suggest that microinjection of NE into CNTS may activate the alpha-adrenorecptor located in CNTS and secondarily produce a depressor effect by attenuating the activity of periphenal sympathetic nervous system.
Blood Pressure/drug effects ; Depression, Chemical ; Kidney/*innervation ; Microinjections ; Norepinephrine/*pharmacology ; Solitary Nucleus/*physiology ; Sympathetic Nervous System/drug effects ; Sympathetic Nervous System/*physiopathology ; Vasomotor System/physiopathology