Loss of GABAergic Signaling by AgRP Neurons to the Parabrachial Nucleus Leads to Starvation

Wu, Qi; Boyle, Maureen P.; Palmiter, Richard D.

doi:10.1016/j.cell.2009.04.022

Cited by 404 publications

(401 citation statements)

References 49 publications

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“…Loss of AgRP neurons results in Fos induction in the same region of the PBN where Fos induction occurs after a single injection of LiCl ( Fig. 3 A and B), in agreement with previous results (13). However, the Fos signal in the PBN neurons was reduced dramatically in Agrp DTR/+ mice to which LiCl had been administered previously for four consecutive days (Fig.…”

Section: Pretreatment With Licl Reduces Fos Induction In the Pbn Aftersupporting

confidence: 81%

“…Activation of AgRP neurons promotes food intake and body weight gain by inhibiting postsynaptic target neurons in the paraventricular hypothalamus (10). Ablation of AgRP neurons by administration of diphtheria toxin (DT) to mice that express the diphtheria toxin receptor (DTR) selectively in AgRP neurons (Agrp DTR mice) results in aphagia and a fatal loss of body weight caused by the hyperactivity of postsynaptic neurons in the parabrachial nucleus (PBN) as a consequence of losing inhibitory GABAergic signals (11)(12)(13). This anorexic response can be prevented by benzodiazepine potentiation of GABA signaling, by genetic blockade of NMDA glutamate receptor signaling in the PBN, or by reducing glutamatergic input or output from the PBN, including knockdown of NMDA expression in the PBN (14).…”

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confidence: 99%

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NR2B subunit of the NMDA glutamate receptor regulates appetite in the parabrachial nucleus

Zheng²,

Srisai

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Diphtheria toxin-mediated, acute ablation of hypothalamic neurons expressing agouti-related protein (AgRP) in adult mice leads to anorexia and starvation within 7 d that is caused by hyperactivity of neurons within the parabrachial nucleus (PBN). Because NMDA glutamate receptors are involved in various synaptic plasticity-based behavioral modifications, we hypothesized that modulation of the NR2A and NR2B subunits of the NMDA receptor in PBN neurons could contribute to the anorexia phenotype. We observed by Western blot analyses that ablation of AgRP neurons results in enhanced expression of NR2B along with a modest suppression of NR2A. Interestingly, systemic administration of LiCl in a critical time window before AgRP neuron ablation abolished the anorectic response. LiCl treatment suppressed NR2B levels in the PBN and ameliorated the local Fos induction that is associated with anorexia. This protective role of LiCl on feeding was blunted in vagotomized mice. Chronic infusion of RO25-6981, a selective NR2B inhibitor, into the PBN recapitulated the role of LiCl in maintaining feeding after AgRP neuron ablation. We suggest that the accumulation of NR2B subunits in the PBN contributes to aphagia in response to AgRP neuron ablation and may be involved in other forms of anorexia.feeding behavior | nausea | NR2B signaling N MDA receptors form glutamate-gated ion channels that mediate many forms of synaptic plasticity under physiological conditions and neuronal death under excitotoxic pathological conditions (1, 2). NMDA receptors are tetrameric complexes composed of two obligatory NR1 subunits and two regulatory NR2 and/or NR3 subunits. Multiple subtypes of NMDA receptors are identified with distinct pharmacological and biophysical properties that are predominantly determined by the type of NR2 subunit (NR2A to NR2D). NR2A and NR2B subunits are the most abundant subunits in the adult brain and differ in channel properties, synaptic localization, and protein interaction elements, all of which can contribute to the induction of synaptic plasticity (3). Some recent studies suggest that NMDA receptors play a major role in regulating feeding behavior and energy homeostasis. For example, antagonism of hindbrain NMDA receptors increases food intake, whereas activation of NMDA receptors in the nucleus tractus solitarius (NTS) is necessary for cholecystokinin-induced reduction of food intake (4, 5). Injection of NMDA receptor agonists into the lateral hypothalamus elicits feeding in satiated animals, whereas NMDA blockade suppresses food intake and can reduce body weight (6). Genetic inactivation of NR1 subunits specifically in agouti-related protein (AgRP) neurons results in marked loss of food intake and body fat and impaired feeding after a fast (7). These findings implicate NMDA receptor signaling within several neuronal circuits in the control of feeding and energy balance.Emerging evidence suggests that a complex neural network including GABAergic AgRP neurons in the hypothalamic arcuate nucleus plays a pivotal role in...

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Section: Pretreatment With Licl Reduces Fos Induction In the Pbn Aftersupporting

confidence: 81%

mentioning

confidence: 99%

NR2B subunit of the NMDA glutamate receptor regulates appetite in the parabrachial nucleus

Zheng²,

Srisai

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…Moreover, the MeA is also a glucose-sensing area of the brain that may respond to states of hypoglycemia, further strengthening a connection with the wellcharacterized glucostatic role of the VMN (62). The LPB also contributes to body weight regulation as demonstrated by the loss of GABAergic signaling to the parabrachial nuclei from agoutirelated polypeptide (AgRP) neurons of the ARC resulting in starvation (59). Given their effect on feeding, the PVN and VMN may be significant efferent targets of the LPB whereby LPB disinhibition could lead to increased excitation of these areas and anorexia.…”

Section: Discussionmentioning

confidence: 99%

Intrahypothalamic pituitary adenylate cyclase-activating polypeptide regulates energy balance via site-specific actions on feeding and metabolism

Resch

Maunze

Gerhardt

et al. 2013

American Journal of Physiology-Endocrinology and Metabolism

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Resch JM, Maunze B, Gerhardt AK, Magnuson SK, Phillips KA, Choi S. Intrahypothalamic pituitary adenylate cyclase-activating polypeptide regulates energy balance via site-specific actions on feeding and metabolism. Am J Physiol Endocrinol Metab 305: E1452-E1463, 2013. First published October 22, 2013; doi:10.1152/ajpendo.00293.2013.-Numerous studies have demonstrated that both the hypothalamic paraventricular nuclei (PVN) and ventromedial nuclei (VMN) regulate energy homeostasis through behavioral and metabolic mechanisms. Receptors for pituitary adenylate cyclase-activating polypeptide (PACAP) are abundantly expressed in these nuclei, suggesting PACAP may be critical for the regulation of feeding behavior and body weight. To characterize the unique behavioral and physiological responses attributed to select hypothalamic cell groups, PACAP was site-specifically injected into the PVN or VMN. Overall food intake was significantly reduced by PACAP at both sites; however, meal pattern analysis revealed that only injections into the PVN produced significant reductions in meal size, duration, and total time spent eating. PACAP-mediated hypophagia in both the PVN and VMN was abolished by PAC1R antagonism, whereas pretreatment with a VPACR antagonist had no effect. PACAP injections into the VMN produced unique changes in metabolic parameters, including significant increases in core body temperature and spontaneous locomotor activity that was PAC1R dependent whereas, PVN injections of PACAP had no effect. Finally, PACAP-containing afferents were identified using the neuronal tracer cholera toxin subunit B (CTB) injected unilaterally into the PVN or VMN. CTB signal from PVN injections was colocalized with PACAP mRNA in the medial anterior bed nucleus of the stria terminalis, VMN, and lateral parabrachial nucleus (LPB), whereas CTB signal from VMN injections was highly colocalized with PACAP mRNA in the medial amygdala and LPB. These brain regions are known to influence energy homeostasis perhaps, in part, through PACAP projections to the PVN and VMN.feeding; activity; temperature; hypothalamus; rat PITUITARY ADENYLATE CYCLASE-ACTIVATING polypeptide (PACAP) is a key regulator of several hypothalamic systems, including stress (1), osmoregulation (17), thermoregulation (21), and body weight (27). PACAP was first discovered to influence energy homeostasis through inhibition of feeding in mice following a single intracerebroventricular (icv) injection of the peptide (39). These results combined with reports of dietspecific alterations of PACAP mRNA expression in the hypothalamic ventromedial nuclei (VMN) suggest that PACAP is responsive to nutritional status and directly tied to metabolic systems linked to energy expenditure (27,40). In addition to reducing food intake, icv administration of PACAP modulates autonomic nerve activity (55) as well as hepatic glucose production (60). As a ligand, PACAP binds to three different G protein-coupled receptors, the PAC1 receptor (PAC1R), and the receptors originally discovered as targets...

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“…AgRP neurons are known to project to multiple regions of the brain, including the arcuate nucleus, the paraventricular nucleus, and neurons in the dorsomedial hypothalamus, lateral hypothalamic area, and the parabrachial nucleus in the hindbrain (51)(52)(53)(54)(55). In particular, AgRP neurons are known to project directly onto POMC neurons in the arcuate nucleus, and inhibit POMC neuronal firing (15,54).…”

Section: Discussionmentioning

confidence: 99%

Modulation of AgRP-neuronal function by SOCS3 as an initiating event in diet-induced hypothalamic leptin resistance

Olofsson

Unger

Cheung

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

123

111

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Chronic consumption of a fat-rich diet leads to attenuation of leptin signaling in hypothalamic neurons, a hallmark feature of cellular leptin resistance. To date, little is known about the temporal and spatial dysregulation of neuronal function under conditions of nutrient excess. We show that agouti-related protein (AgRP)-expressing neurons precede proopiomelanocortin neurons in developing diet-induced cellular leptin resistance. High-fat diet-induced up-regulation of suppressor of cytokine signaling-3 (SOCS3) occurs in AgRP neurons before proopiomelanocortin and other hypothalamic neurons. SOCS3 expression in AgRP neurons increases after 2 d of high-fat feeding, but reduces after switching to a low-fat diet for 1 d. Consistently, transgenic overexpression of SOCS3 in AgRP neurons produces metabolic phenotypes resembling those observed after short-term high-fat feeding. We further show that AgRP neurons are the predominant cell type situated outside the blood-brain barrier in the mediobasal hypothalamus. AgRP neurons are more responsive to low levels of circulating leptin, but they are also more prone to development of leptin resistance in response to a small increase in blood leptin concentrations. Collectively, these results suggest that AgRP neurons are able to sense slight changes in plasma metabolic signals, allowing them to serve as first-line responders to fluctuation of energy intake. Furthermore, modulation of SOCS3 expression in AgRP neurons may play a dynamic and physiological role in metabolic fine tuning in response to short-term changes of nutritional status.M ost common forms of obesity, including diet-induced obesity, are associated with hyperleptinemia and impairment of leptin signaling in hypothalamic neurons, the hallmark feature of cellular leptin resistance. Suppressor of cytokine signaling-3 (SOCS3), a direct transcriptional product of STAT3, is up-regulated in the hypothalamus of diet-induced obese animals (1, 2). Mice with heterozygous mutation of the Socs3 gene, neuronal, or proopiomelanocortin (POMC)-specific deletion of the Socs3 gene are hypersensitive to leptin and resistant to diet-induced obesity (3-5). Conversely, up-regulation of SOCS3 in POMC neurons of chow-fed mice leads to increased body adiposity (6). In addition, wide-spread up-regulation of SOCS3 has been shown to be associated with neuronal inflammation in diet-induced obese animals (7). Thus SOCS3, which is up-regulated in chronic obesity, is commonly thought to play a pathophysiological role in obesity-associated leptin resistance.Multiple neuronal subtypes in several regions of the hypothalamus, including the arcuate nucleus, ventromedial hypothalamus, dorsomedial hypothalamus, and lateral hypothalamic area, have been implicated in the regulation of energy balance and leptin action (8,9). A number of hypothalamic neurons and extrahypothalamic neurons express functional leptin receptor (10, 11). Among these neurons, POMC and agouti-related protein (AgRP) neurons are two key arcuate neuronal subtypes. POMC and AgRP neu...

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Loss of GABAergic Signaling by AgRP Neurons to the Parabrachial Nucleus Leads to Starvation

Cited by 404 publications

References 49 publications

NR2B subunit of the NMDA glutamate receptor regulates appetite in the parabrachial nucleus

NR2B subunit of the NMDA glutamate receptor regulates appetite in the parabrachial nucleus

Intrahypothalamic pituitary adenylate cyclase-activating polypeptide regulates energy balance via site-specific actions on feeding and metabolism

Modulation of AgRP-neuronal function by SOCS3 as an initiating event in diet-induced hypothalamic leptin resistance

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