Role of mGluR5 in laterocapcular division of central nucleus of amygdala in fentanyl-induced hyperalgesia in rats / 中南大学学报(医学版)

To investigate the role of metabotropic glutamate receptor 5 (mGluR5) in laterocapcular division of the central nucleus of amygdala (CeLC) in fentanyl-induced hyperalgesia in rats. 
 Methods: A total of 12 Sprague-Dawley male rats (60-100 g) were randomly divided into a normal group 1 (n=6) and an opioid-induced hyperalgesia (OIH) group 1 (n=6). The OIH group 1 was injected with fentanyl through the lower neck skin to build OIH model, and the normal group 1 was given the same volume of saline. After 6.5 h, paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) were tested to verify the success of the induction of OIH. Then rats were sacrificed and the right CeLC tissue were taken for detection of the mGluR5 by Western blotting. Forty SD male rats were randomly divided into 4 groups (n=10 each): an OIH+DMSO, an OIH+MTEP (3.0 μg), an OIH+MTEP (7.5 μg) and an OIH+MTEP (15.0 μg) group. MTEP was a selective antagonist of mGluR5. Catheterization in the right CeLC was first performed. After one-week recovery, OIH was induced. Then 0.5 μL DMSO, MTEP 3.0 μg, MTEP 7.5 μg and MTEP 15.0 μg were administrated through the CeLC catheter accordingly. PWMT and PWTL were tested at pre-OIH, 6 h after OIH and post-drug. Then the expression levels of mGluR5 of CeLC tissue were analyzed by Western blotting. Another 8 SD male rats were randomly divided into a normal group 2 and an OIH group 2 (n=4 each). The rats were induced OIH by injecting of fentanyl while rats in the normal group 2 were injected with same volume of saline. The miniature excitatory postsynaptic currents (mEPSCs) of the 2 groups' neurons in the right CeLC region were recorded by whole cell voltage-clamp before and after the administration of MTEP in brain slice.
 Results: Compared with the normal group 1, the PWTL and PWMT were significantly decreased and the expression of mGluR5 was apparently increased in the OIH group 1 (P<0.05). The PWMT and PWTL were significantly decreased in each group and indicated success of OIH model (P<0.05). The expression of mGluR5 in the CeLC was increased. MTEP reversed these changes in a dose-dependent way (P<0.05). Compared with the normal group 2, the amplitude and frequency of mEPSCs in the OIH group 2 were significantly increased (P<0.05) and they were reversed by MTEP (P<0.05). 
 Conclusion: mGluR5 in the CeLC may be involved in the maintenance of OIH. Inhibition of the activity of mGluR5 in the CeLC may alleviate the symptoms of fentanyl-induced hyperalgesia.

Corticotrophin-releasing hormone neurons in the central amygdala mediate morphine withdrawal-induced negative emotions / 生理学报

Drugs of abuse leads to adaptive changes in the brain stress system, and produces negative affective states including aversion and anxiety after drug use is terminated. Corticotrophin-releasing hormone (CRH) is the main transmitter in control of response to stressors and is neuronal enriched in the central amygdala (CeA), a sub-region of the extended amygdala playing an important role in integrating emotional information and modulating stress response. The effect of CRH neurons in CeA on the negative emotions on morphine naïve and withdrawal mice is unclear. Thus, we utilized CRH-Cre transgenic mice injected with AAV-mediated Designer Receptors Exclusively Activated By Designer Drugs (DREADDs) to chemogenetically manipulate CRH neurons in CeA. And methods of behavior analysis, including conditioned place aversion (CPA), elevated plus maze and locomotor activity tests, were used to investigate morphine withdrawal-induced negative emotions in mice. The results showed that, inhibiting CRH neurons of CeA decreased the formation of morphine withdrawal-induced CPA, as well as the anxiety level of CRH-Cre mice. Furthermore, specifically activating CRH neurons in CeA evoked CPA and anxiety of morphine naïve mice. Neither inhibiting nor activating CRH neurons had effects on their locomotor activity. These results suggest that CRH neurons in CeA are involved in the mediation of morphine withdrawal-induced negative emotion in mice, providing a theoretical basis for drug addiction and relapse mechanism.

Altered Neuronal Activity in the Central Nucleus of the Amygdala Induced by Restraint Water-Immersion Stress in Rats / 神经科学通报·英文版

Restraint water-immersion stress (RWIS), a compound stress model, has been widely used to induce acute gastric ulceration in rats. A wealth of evidence suggests that the central nucleus of the amygdala (CEA) is a focal region for mediating the biological response to stress. Different stressors induce distinct alterations of neuronal activity in the CEA; however, few studies have reported the characteristics of CEA neuronal activity induced by RWIS. Therefore, we explored this issue using immunohistochemistry and in vivo extracellular single-unit recording. Our results showed that RWIS and restraint stress (RS) differentially changed the c-Fos expression and firing properties of neurons in the medial CEA. In addition, RWIS, but not RS, induced the activation of corticotropin-releasing hormone neurons in the CEA. These findings suggested that specific neuronal activation in the CEA is involved in the formation of RWIS-induced gastric ulcers. This study also provides a possible theoretical explanation for the different gastric dysfunctions induced by different stressors.

Acute physical and psychological stress effects on visceral hypersensitivity in male rat: role of central nucleus of the amygdala / Efeitos agudos do estresse físico e psicológico na hipersensibilidade visceral em rato macho: papel do núcleo central da amídala

ABSTRACT Objective: The aim of this study was to investigate the effects of acute physical and psychological stress and temporary central nucleus of the amygdala (CeA) block on stress-induced visceral hypersensitivity. Methods: Forty two male Wistar rats were used in this study. Animals were divided into 7 groups (n = 6); 1 - Control, 2 - physical stress, 3 - psychological stress, 4 - sham, 5 - lidocaine, 6 - lidocaine + physical stress and 7 - lidocaine + psychological stress. Stress induction was done using a communication box. Results: Abdominal withdrawal reflex (AWR) score was monitored one hour after stress exposure. AWR score significantly heightened at 20, 40 and 60 mmHg in the psychological stress group compared with control (p < 0.05), while, it was almost unchanged in other groups. This score was strikingly decreased at 20, 40 and 60 mmHg in lidocaine + psychological stress group compared with psychological stress with no tangible response on physical stress. Total stool weight was significantly increased in psychological stress group compared with control (0.72 ± 0.15, 0.1 ± 0.06 g) (p < 0.05), but it did not change in physical stress compared to control group (0.16 ± 0.12, 0.1 ± 0.06 g) (p < 0.05). Concomitant use of lidocaine with stress followed the same results in psychological groups (0.18 ± 0.2, 0.72 ± 0.15 g) (p < 0.05), while it did not have any effect on physical stress group (0.25 ± 0.1, 0.16 ± 0.12 g) (p < 0.05). Conclusions: Psychological stress could strongly affect visceral hypersensitivity. This effect is statistically comparable with physical stress. Temporary CeA block could also reduce visceral hypersensitivity post-acute psychological stress.

RESUMEN Objetivo: O objetivo desse estudo foi investigar os efeitos do estresse físico e psicológico agudo e bloqueio temporário do núcleo central da amídala (CeA) na hipersensibilidade visceral induzida por estresse. Métodos: Quarenta e dois ratos Wistar machos foram empregados nesse estudo. Os animais foram divididos em 7 grupos (n = 6): 1 - Controle, 2 - estresse físico, 3 - estresse psicológico, 4 - simulacro, 5 - lidocaína, 6 - lidocaína + estresse físico e 7 - lidocaína + estresse psicológico. A indução do estresse foi feita com o uso de uma caixa de comunicação. Resultados: O escore do reflexo de retirada abdominal (RRA) foi monitorado uma hora depois da exposição ao estresse. O escore RRA aumentou significativamente a 20, 40 e 60 mmHg no grupo de estresse psicológico versus controle (p < 0,05), enquanto que praticamente permaneceu inalterado nos demais grupos. Esse escore diminuiu drasticamente a 20, 40 e 60 mmHg no grupo de lidocaína + estresse psicológico versus estresse psicológico, sem resposta tangível no estresse físico. O peso total das fezes aumentou significativamente no grupo de estresse psicológico versus controle (0,72 ± 0,15, 0,1 ± 0,06 g) (p < 0,05), mas não houve mudança no grupo de estresse físico versus controle (0,16 ± 0,12, 0,1 ± 0,06 g) (p < 0,05). O uso simultâneo da lidocaína com o estresse acompanhou os mesmos resultados nos grupos psicológicos (0,18 ± 0,2, 0,72 ± 0,15 g) (p < 0,05), enquanto que não foi observado qualquer efeito no grupo de estresse físico (0,25 ± 0,1, 0,16 ± 0,12 g) (p < 0,05). Conclusões: O estresse psicológico pode afetar fortemente a hipersensibilidade visceral. Esse efeito é estatisticamente comparável com o estresse físico. Um bloqueio temporário do CeA também pode reduzir a hipersensibilidade visceral pós-estresse psicológico agudo.

A regulação da proteína quinase ativada pelo AMP (AMPK) no CeA e os efeitos sobre o controle da ingestão alimentar e gasto energético / Regulation of AMP-activated protein kinase (AMPK) in the CeA and the effects on food intake control and energy expenditure

Resumo: A AMP-activated protein kinase (AMPK) regula o balanço energético por ações no hipotálamo. Sua ativação está ligada ao aumento da ingestão alimentar e sua inibição leva a redução da ingestão alimentar. Recentes evidências demonstram que outras regiões do sistema nervoso podem contribuir para o controle da ingestão alimentar. O núcleo central da amígdala (CeA) é parte integrante do sistema dopaminérgico de recompensa e juntamente com o hipotálamo participa do controle da homeostase energética. Na amígdala vias moleculares como a via da insulina participam do controle da ingestão alimentar, contudo ainda não foi avaliado se a AMPK poderia contribuir com esse controle. Em vista disso, o presente estudo avaliou a possível fosforilação da AMPK no CeA e sua participação no controle da ingestão alimentar em resposta a diversas situações. A AMPK estava expressa no CeA. O jejum aumentou a fosforilação em treonina da AMPK?1/2Thr172 e a realimentação reduziu essa fosforilação. A injeção de glicose no CeA diminuiu a fosforilação em AMPK?1/2Thr172, ao passo que, a injeção de 2DG aumentou essa fosforilação, assim como a ingestão alimentar. A injeção de grelina no CeA aumentou a ingestão alimentar e a fosforilação em AMPK?1/2Thr172. Esse resultado foi acompanhado pelo aumento da expressão gênica do NPY e redução de ocitocina. Em contrapartida, a insulina reduziu a fosforilação em AMPK?1/2Thr172 no CeA. A ativação farmacológica da AMPK no CeA, com AICAR, aumentou a ingestão como esperado. A infusão crônica de MTII reduziu a massa corporal, a ingestão e a fosforilação em AMPK?1/2Thr172 no CeA. O tratamento por 14 dias com siRNA-AMPK?2 no CeA, inibiu a expressão gênica da AMPK e reduziu a massa corporal. Essa redução foi acompanhada de aumento na expressão gênica de UCP1 no tecido adiposo marrom sem alteração na ingestão alimentar. Em adição, houve redução na expressão gênica de NPY e aumento de ocitocina no CeA. Esses resultados sugerem que a ativação da AMPK no CeA, participa do controle da homeostase energética por modular a ingestão alimentar em reposta a ação de nutrientes e hormônios como grelina e insulina(AU)

Abstract: AMP-activated protein kinase (AMPK) is a cellular energy sensor that regulates energy balance at cellular and whole body nivel. Several studies demonstrate that hypothalamic AMPK participates in the control of food intake in response to nutrients and hormones such as insulin and ghrelin. Increased AMPK activity in hypothalamus is associated with enhance in food intake and its inhibition leads to reduced food intake. Recent evidence demonstrates that other regions from central nervous system may contribute to control energy metabolism and food intake. The central nucleus of the amygdala (CeA) is part of the dopaminergic reward system and jointly with the hypothalamus participates in control of food intake. In amygdala molecular pathways such as insulin pathway participate in the control of food intake, however other cellular pathways, such as AMPK may contribute to this control. In this sense, the present study investigated AMPK activation in CeA and its participation in food intake control. Fasting increased phosphorylation in Thr172 of AMPK?1/2 and refeeding reduced this phosphorylation. Injection of glucose in CeA decreased the phosphorylation in Thr172 of AMPK?1/2, whereas 2DG injection increased this phosphorylation as well as food intake. Ghrelin injection in CeA increased food intake and Thr172 phosphorylation of AMPK?1/2. In adiction, NPY gene expression was increased and oxytocin gene expression was lower. In contrast, insulin reduced Thr172 phosphorylation of AMPK?1/2 in CeA. As expected, AMPK pharmacological activation in CeA with AICAR increased food intake. Chronic injection of MTII in CeA reduced body mass, food intake and phosphorylation in Thr172 of AMPK?1/2. Further, knocking down Alpha 1/2 AMPK in the CeA for 14 days was sufficient to decrease body mass without altering food intake. AMPK?2 and NPY gene expression in CeA was reduced and oxytocin gene expression in CeA and UCP-1 in BAT was increased. These results suggest that once active in CeA, AMPK participates in control of energy homeostasis by modulating food intake in response to nutrients and hormones such as ghrelin and insulin(AU)

Functional Connectivity of Basolateral Amygdala Neurons Carrying Orexin Receptors and Melanin-concentrating Hormone Receptors in Regulating Sociability and Mood-related Behaviors

Chronic stress induces changes in neuronal functions in specific brain regions regulating sociability and mood-related behaviors. Recently we reported that stress-induced persistent upregulation of the neuropeptides orexin and melanin-concentrating hormone (MCH) in the basolateral amygdala (BLA) and the resulting activation of orexin receptors or MCH receptors within the BLA produced deficits in sociability and mood-related behaviors. In the present study, we investigated the neural targets that were innervated by BLA neurons containing orexin receptors or MCH receptors. The viral vector system AAV2-CaMKII-ChR2-eYFP was injected into the BLA to trace the axonal tracts of BLA neurons. This axon labeling analysis led us to identify the prelimbic and infralimbic cortices, nucleus accumbens (NAc), dorsal striatum, paraventricular nucleus (PVN), interstitial nucleus of the posterior limb of the anterior commissure, habenula, CA3 pyramidal neurons, central amygdala, and ventral hippocampus as the neuroanatomical sites receiving synaptic inputs of BLA neurons. Focusing on these regions, we then carried out stimulus-dependent c-Fos induction analysis after activating orexin receptors or MCH receptors of BLA neurons. Stereotaxic injection of an orexin receptor agonist or an MCH receptor agonist in the BLA induced c-Fos expression in the NAc, PVN, central amygdala, ventral hippocampus, lateral habenula and lateral hypothalamus, which are all potentially important for depression-related behaviors. Among these neural correlates, the NAc, PVN and central amygdala were strongly activated by stimulation of orexin receptors or MCH receptors in the BLA, whereas other BLA targets were differentially and weakly activated. These results identify a functional connectivity of BLA neurons regulated by orexin and MCH receptor systems in sociability and mood-related behaviors.

Repeated binge-like ethanol administration during adolescence cause decreased C-Fos immunoreactivity in amygdala and arcuate nucleus in adult Sprague-Dawley rats / La administración repetida de etanol, tipo atracón, durante la adolescencia provoca descenso en la expresión de C-Fos en la amígdala y núcleo arqueado de ratas Sprague-Dawley adultas

Binge alcohol drinking during adolescence has been associated with neurotoxicity and increased risk for the development of alcohol use disorders. There is evidence that acute and chronic ethanol administration alters c-fos expression, an indirect index of cellular activity, in different brain regions in adult rats. We evaluate here if a binge-like pattern of ethanol exposure during adolescence has a relevant impact on basal and/or ethanol-stimulated regional c-fos activity during adulthood. For that aim, Sprague-Dawley rats PND 25 were saline pre-treated, (SP group) or binge-ethanol pre-treated (BEP group) for two­consecutive days, at 48-h intervals, over a 14-day period (PND 25 to PND 38). At adult stage (PND 63) and following 25 ethanol-free days, we evaluated c-fos immunoreactivity in response to saline or acute ethanol (1.5 or 3.0 g/kg) in the hypothalamus and amygdala. We found that acute ethanol administration dose-dependently increased c-fos activity in the the Paraventricular nucleus of the hypothalamus (PVN). Interestingly, binge-ethanol exposure during adolescence significantly reduced basal c-fos activity during adulthood in the Central nucleus of the amygdala (CeA) and the Arcuate nucleus of hypothalamus (Arc). We conclude that binge-like ethanol administration during adolescence causes long-term disturbances in basal neural activity in brain areas critically involved with ethanol consumption.

El consumo en atracón durante la adolescencia está asociado con neurotoxicidad y con el riesgo de desarrollar un trastorno en el uso de alcohol. Diversos estudios muestran que la administración aguda y crónica de alcohol en ratas adultas altera la expresión de c-fos, un marcador indirecto de actividad celular, en diferentes áreas cerebrales. Nosotros evaluamos si el patrón de consumo de alcohol en atracón durante la adolescencia tiene un impacto en la actividad basal de c-fos en esas regiones activadas por el alcohol. Utilizamos ratas Sprague-Dawley en su día post-natal 25 (PND25) tratadas con suero salino (grupo SP) o con etanol tipo atracón (grupo BEP) durante dos días consecutivos, en intervalos de 48 h, durante 14 días (PND25- PND38). En la edad adulta (PND63) y después de 25 días sin etanol, evaluamos la inmunorreactividad para c-fos en respuesta a una administración aguda de suero salino o etanol (1,5 ó 3,0 g/kg) en diferentes regiones cerebrales. La administración de alcohol incrementó de manera dosis-dependiente la actividad de c-fos en el núcleo paraventricular del hipotálamo. Además la exposición a etanol tipo atracón durante la adolescencia disminuyó la actividad basal de c-fos en la adultez en el núcleo central de la amígdala y en el núcleo arqueado del hipotálamo. Concluimos que el consumo de alcohol en atracón durante la adolescencia causa problemas a largo plazo en la actividad basal de regiones cerebrales implicadas en el consumo de alcohol.

µ-opioid receptors in the central nucleus of the amygdala regulate food rather than water intake in rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of µ-opioid receptors (µ-ORs) in the central nucleus of the amygdala (CeA) on feeding and drinking behaviors in rats and evaluate the role of glutamate signaling in opioid-mediated ingestive behaviors.</p><p><b>METHODS</b>Stainless steel cannulas were implanted in the unilateral CeA for microinjection of different doses of the selective µ-OR agonist DAMGO in satiated or water-deprived male SD rats. The subsequent food intake or water intake of the rats was measured at 60, 120, and 240 min after the injection. The rats receiving microinjections of naloxone (NTX, a nonselective opioid antagonist) or D-AP-5 (a selective N-methyl-D-aspartic acid-type glutamate receptor antagonist) prior to DAMGO microinjection were tested for food intake at 60, 120, and 240 min after the injections.</p><p><b>RESULTS</b>Injections of DAMGO (1-4 nmol in 0.5 µl) into the CeA significantly increased food intake in satiated rats, but did not affect water intake in rats with water deprivation. NTX (26.5 nmol in 0.5 µl) injected into the CeA antagonized DAMGO-induced feeding but D-AP-5 (6.3-25.4 nmol in 0.5 µl) injections did not produce such an effect.</p><p><b>CONCLUSION</b>µ-ORs in the CeA regulate food intake rather than water intake in rats, and the orexigenic role of µ-ORs is not dependent on the activation of the NMDA receptors in the CeA.</p>