Control of Emotion and Wakefulness by Neurotensinergic Neurons in the Parabrachial Nucleus / 神经科学通报·英文版

The parabrachial nucleus (PBN) integrates interoceptive and exteroceptive information to control various behavioral and physiological processes including breathing, emotion, and sleep/wake regulation through the neural circuits that connect to the forebrain and the brainstem. However, the precise identity and function of distinct PBN subpopulations are still largely unknown. Here, we leveraged molecular characterization, retrograde tracing, optogenetics, chemogenetics, and electrocortical recording approaches to identify a small subpopulation of neurotensin-expressing neurons in the PBN that largely project to the emotional control regions in the forebrain, rather than the medulla. Their activation induces freezing and anxiety-like behaviors, which in turn result in tachypnea. In addition, optogenetic and chemogenetic manipulations of these neurons revealed their function in promoting wakefulness and maintaining sleep architecture. We propose that these neurons comprise a PBN subpopulation with specific gene expression, connectivity, and function, which play essential roles in behavioral and physiological regulation.

Relationship between choline acetyltransferase positive neurons in parabrachial nucleus and development of fear memory in mice / 中华麻醉学杂志

Objective:To evaluate the relationship between choline acetyltransferase (ChAT) positive neurons in parabrachial nucleus and development of fear memory in mice.Methods:Eighteen healthy male ChAT-ires-cre mice, aged 8-9 weeks, weighing 22-25 g, were divided into 3 groups ( n=6 each) using a random number table method: Cre-dependent AAV-DIO-hM 3Dq-mcherry (Gq) virus/clozapine-N-oxide (CNO) group (group Gq/CNO), Gq/normal saline (NS) group (group Gq/NS) and Cre-dependent AAV-DIO-mcherry (mc) virus/CNO group (group mc/CNO). Gq virus was injected into parabrachial nucleus, and CNO 2 mg/kg was injected intraperitoneally 3 weeks later in group Gq/CNO.Gq virus was injected into parabrachial nucleus, and the equal volume of normal saline was injected intraperitoneally 3 weeks later in group Gq/NS.In group mc/CNO, mc virus was injected into parabrachial nucleus, and CNO 2 mg/kg was injected intraperitoneally 3 weeks later.The fear conditioning test was performed at 30 min after intraperitoneal injection in all the 3 groups.The brains were then removed and sliced.The virus expression and areas of the brain projected by ChAT positive neurons were observed. Results:Compared with group Gq/CNO, the percentage of freezing time was significantly increased during testing phase in Gq/NS and mc/CNO groups ( P<0.05). Gq/mc virus carrying fluorescent protein mcherry was expressed in parabrachial nucleus and was co-expressed with mcherry-ChAT.The fibers of ChAT positive neurons projected to the red nucleus, substantia nigra, central amygdala, anterodorsal thalamic nucleus and bed nucleus of stria terminalis. Conclusion:The ChAT positive neurons in parabrachial nucleus are involved in the regulation of the development of fear memory in mice, which can impair fear memory, and the regulation is carried out probably through central amygdala.

Regulatory effects of PB on sleep and wakefulness / 中国药理学通报

The parabrachial nucleus (PB)is made up of gray matter around the Pons combination(BC),mainly consisting of glutamatergic,GABAergic and enkephalinergic neurons.PB is connected to hypothalamus and basal forebrain through a network of nerve fibers.Specific lesion of the entire parabrachial complex in animals leads to a deep coma.PB also projects to the non-rapid eye movement(NREM)-related regions including the ven-trolateral preoptic,and receives the projections from the parafa-cial zone.Activation of the GABAergic neurons in parafacial zone can promote NREM sleep,which indicates that PB partici-pates in NREM sleep.Furthermore,the lateral PB is actived when rapid eye movement(REM)sleep is deprived.In conclu-sion,PB participates in regulating wakefulness, NREM and REM sleep.This review summarizes the advances in the roles of PB in sleep-wake regulation.

Role of α2-adrenoceptors in the lateral parabrachial nucleus in the control of body fluid homeostasis

Central α2-adrenoceptors and the pontine lateral parabrachial nucleus (LPBN) are involved in the control of sodium and water intake. Bilateral injections of moxonidine (α2-adrenergic/imidazoline receptor agonist) or noradrenaline into the LPBN strongly increases 0.3 M NaCl intake induced by a combined treatment of furosemide plus captopril. Injection of moxonidine into the LPBN also increases hypertonic NaCl and water intake and reduces oxytocin secretion, urinary sodium, and water excreted by cell-dehydrated rats, causing a positive sodium and water balance, which suggests that moxonidine injected into the LPBN deactivates mechanisms that restrain body fluid volume expansion. Pretreatment with specific α2-adrenoceptor antagonists injected into the LPBN abolishes the behavioral and renal effects of moxonidine or noradrenaline injected into the same area, suggesting that these effects depend on activation of LPBN α2-adrenoceptors. In fluid-depleted rats, the palatability of sodium is reduced by ingestion of hypertonic NaCl, limiting intake. However, in rats treated with moxonidine injected into the LPBN, the NaCl palatability remains high, even after ingestion of significant amounts of 0.3 M NaCl. The changes in behavioral and renal responses produced by activation of α2-adrenoceptors in the LPBN are probably a consequence of reduction of oxytocin secretion and blockade of inhibitory signals that affect sodium palatability. In this review, a model is proposed to show how activation of α2-adrenoceptors in the LPBN may affect palatability and, consequently, ingestion of sodium as well as renal sodium excretion.

Role of the serotoninergic system in the sodium appetite control

The present article reviews the role of the serotoninergic system in the regulation of the sodium appetite. Data from the peripheral and icv administration of serotoninergic (5-HTergic) agents showed the participation of 5-HT2/3 receptors in the modulation of sodium appetite. These observations were extended with the studies carried out after brain serotonin depletion, lesions of DRN and during blockade of 5-HT2A/2C receptors in lateral parabrachial nucleus (LPBN). Brain serotonin depletion and lesions of DRN increased the sodium appetite response, in basal conditions, after sodium depletion and hypovolemia or after beta-adrenergic stimulation as well. These observations raised the hypothesis that the suppression of ascending pathways from the DRN, possibly, 5-HTergic fibers, modifies the angiotensinergic or sodium sensing mechanisms of the subfornical organ involved in the control of the sodium appetite. 5-HTergic blockade in LPBN induced to similar results, particularly those regarded to the natriorexigenic response evoked by volume depletion or increase of the hypertonic saline ingestion induced by brain angiotensinergic stimulation. In conclusion, many evidences lead to acceptation of an integrated participation resulting of an interaction, between DRN and LPBN, for the sodium appetite control.

Este artigo revisa o papel do sistema serotoninérgico no controle do apetite ao sódio. Dados derivados da administração periférica e icv de agentes serotoninérgicos demonstraram a participação de receptores 5-HT2/3 na modulação do apetite ao sódio. Estas observações foram estendidas com os estudos realizados após a depleção cerebral de serotonina, lesões do NDR e durante o bloqueio 5-HT2A/2C no núcleo parabraquial lateral (NPBL). A depleção cerebral de serotonina e as lesões do NDR aumentaram o apetite ao sódio, em condições basais, após depleção de sódio, durante a hipovolemia ou após a estimulação beta-adrenérgica. Estas evidências suscitaram a hipótese de que a supressão de vias ascendentes do NDR, possivelmente 5-HT, alteram os mecanismos angiotensinérgicos e a atividade dos sensores de sódio do órgão subfornicial envolvidos no controle do apetite ao sódio. O bloqueio serotoninérgico no NPBL induziu a resultados similares, particularmente aqueles relacionados com a resposta natriorexigênica provocada pela depleção de volume ou o aumento da ingestão de salina hipertônica induzida pela estimulação angiotensinérgica cerebral. Em resumo, as evidências convergem para a admissão de uma participação integrada resultante da interação recíproca entre NDR e NPBL objetivando controlar o apetite ao sódio.

Effect of Microinjection of GABA into Parabrachial Nuclei in Rats on Blood Pressure and Heart Rate / 华中科技大学学报(医学版)

Experiments were carried out in 31 urethane anesthetized, Suxamethonium chloride paralyzed and artificially ventilated rats. The results were as follows: microinjection of γ-amino butyric acid (GABA) into parabrachial nuclei (NPB) markedly decreased the mean arterial pressure (MAP) (P＜0. 001), while the microinjection of bicuculine (Bic) into NPB caused a significant increase in MAP (P＜0. 001). The depressor effect of GABA could be blocked by preinjection of Bic in NPB. The above agents microinjected into NPB had no significant effect on heart rate (P＞0. 05). The results indicated that: (1) GABA in NPB exerts tonic depressor effect; (2) Endogenous GABA in NPB exerts tonic depressor action and takes part in maintenance of normal blood pressure level.

THE CENTRAL CONNECTIONS AND FUNCTIONAL CONSIDERATIONS OF THE DORSAL COMMISSURAL NUCLEUS OF THE RAT——A HRP METHOD STUDY / 解剖学报

HRP solution was injected into the dorsal commissural nucleus (DCN) of segment L_6 or S_1 of the spinal cord and laterodorsal tegmental area(TLD)——take the Barrington's nucleus as its center and lateral parabrachial nucleus (PBL) of the rostral pons in different individuals of the rats. After HRP was injected into the DCN, labelled neurons and dense terminals were found in Barrington's nucleus, and labelled terminals appeared in the PBL. When the unilateral TLD was injected the labelled cells and terminals were found in the DCN and bilateral intermediate zone (IM), and formed a band of labelled neurons and terminals. When the PBL was injected the labelled neurons were observed in the DCN and bilateral IM. A few labelled neurons were found in lamina Ⅰ in the latter two experimental groups.Based on the present and previous studies, the authors got the following understandings:1. Morphylogically, the present study for the first time demonstrated that, the micturition reflex arch through the pontine consists of following parts: the primary afferent neurons of the bladder→secondary relay neurons of DCN→Barrington's nucleus→IM (mainly IML) parasympathetic preganglionic neurons→parasympathetic postganglionic neurons.2. According to the present and previous researches, the authors conjecture that, the secondary fibers of visceral sensation of the pelvic organs originate from the neurons of DCN, IM and lamina I and project into the PBL.3. According to the facts mentioned above, we presume that the DCN and bilateral IM constitute a complex and named it the 'visceral field', and which is closely associated with the pelvic organs. This field has widespread connections with the peripheral efferent and afferent nerves. On the other hand, i t contains a lot of relay neurons projecting into Barrington's nucleus and PBL and receives the terminals of descending fibers of the neurons of the Barrington's nucleus. The descending fibers also project into the Onuf's nucleus.In addition, the present study disscussed the complicated functions of the DCN systematically.

SPINAL PROJECTIONS TO THE PARABRACHIAL NUCLEUS IN THE RAT——HRP AND FLUOROGOLD RETROGRADE TRACT TRACING STUDY / 解剖学报

By introducing a mixture of WGA-HRP and HRP or fluorogold into the parabrachial nucleus, the cell origin of the spinoparabrachial projections in the rat have been carefully examined. The labelled neurons were found in bilateral spinal gray matter, lateral spinal nucleus and lateral cervical nucleus with contralateral predominance. They were mainly located in lamina I, lamina II, lamina IV, lamina V and lamina VII of the gray matter and also in the gray matter commissure posterior to the central canal. Comparing the distribution patterns of the projection neurons in the cervical, thoracic, lumbar and sacral segments, we did not find any distinct differences. The fact that the parabrachial nucleus receives a wide extensive projections form the spinal segments suggests that the spino-parabrachial pathways are possibly involved in the transmission of multiple sensory inputs.

SPINAL PROJECTION OF NEUROPEPTIDE Y-AND NEUROTENSIN-IMMUNOREACTIVE NEURONS TO THE PARABRACHIAL NUCLEUS IN THE RAT / 解剖学报

In this study a combination of HRP retrograde tract tracing and immunocytochemistry was employed to investigate the afferent projections of neuropeptide Y(NPY) -and neurotensin (NT)-immunoreactive(ir) neurons in the cervical, thoracic, lumbar and sacral spinal segments to the parabrachial nucleus in the rat. It was demonstrated that the retrogradely labeled neurons were scattered in bilateral laminae I, II, IV, V, VII, gray matter commissure dorsal to the central canal, lateral cervical nucleus and lateral spinal nucleus. The NPY-ir neurons were situated in bilateral lamina I, superficial portion of the lamina II, lateral cervical nucleus and lateral spinal nucleus. The NT-ir cells were seen in bilateral lamina I and lamina II of dorsal horn. In lamina I, lateral cervical nucleus and lateral spinal nucleus a few of NPY-HRP double labelled neurons could be observed. Individuals of NT-HRP double labeled neurons were identified only in lamina I. The results of this study suggest that NPY and NT neurons probably involved in the nociceptive transmission of the spino-parabrachial pathway.