Excitatory/inhibitory equilibrium of the central amygdala nucleus gates anti-depressive and anxiolytic states in the hamster

Astrocyte secretes IL-6 to modulate PSD-95 palmitoylation in basolateral amygdala and depression-like behaviors induced by peripheral nerve injury

Dysfunction of glutamatergic synaptic plasticity in basolateral amygdala (BLA) constitutes a critical pathogenic mechanism underlying the depression-like behaviors induced by chronic pain. Astrocytes serve as an important supporting cell modulating glutamatergic synaptic transmission. Here, we found that peripheral spared nerve injury (SNI) induced astrocyte activation to release IL-6 in BLA. Inhibition of astrocyte activity attenuated SNI-induced IL-6 overexpression and depression-like behaviors. Moreover, SNI enhanced the abundance of DHHC2 in synaptosome and DHHC3 in Golgi apparatus, promoted PSD-95 palmitoylation, and increased the recruitment of GluR1 and NR2B at synapses. Suppression of IL-6 or PSD-95 palmitoylation attenuated the synaptic accumulation of GluR1 and NR2B in BLA and improved depression-like behaviors induced by SNI. Furthermore, IL-6 downstream PI3K increased the expression of DHHC3 in Golgi apparatus and facilitated the interaction of palmitoylated PSD-95 with GluR1 and NR2B at synapses. These findings collectively suggested that SNI activated astrocyte to release IL-6 in BLA, which promoted PSD-95 palmitoylation and enhanced the synaptic trafficking of GluR1 and NR2B, and subsequently mediated the depression-like behaviors induced by nerve injury.

Neurobiology and consequences of social isolation stress in animal model-A comprehensive review

The brain is a vital organ, susceptible to alterations under genetic influences and environmental experiences. Social isolation (SI) acts as a stressor which results in alterations in reactivity to stress, social behavior, function of neurochemical and neuroendocrine system, physiological, anatomical and behavioral changes in both animal and humans. During early stages of life, acute or chronic SIS has been proposed to show signs and symptoms of psychiatric and neurological disorders such as anxiety, depression, schizophrenia, epilepsy and memory loss. Exposure to social isolation stress induces a variety of endocrinological changes including the activation of hypothalamic-pituitary-adrenal (HPA) axis, culminating in the release of glucocorticoids (GCs), release of catecholamines, activation of the sympatho-adrenomedullary system, release of Oxytocin and vasopressin. In several regions of the central nervous system (CNS), SIS alters the level of neurotransmitter such as dopamine, serotonin, gamma aminobutyric acid (GABA), glutamate, nitrergic system and adrenaline as well as leads to alteration in receptor sensitivity of N-methyl-D-aspartate (NMDA) and opioid system. A change in the function of oxidative and nitrosative stress (O&NS) mediated mitochondrial dysfunction, inflammatory factors, neurotrophins and neurotrophicfactors (NTFs), early growth response transcription factor genes (Egr) and C-Fos expression are also involved as a pathophysiological consequences of SIS which induce neurological and psychiatric disorders.

Loss of Intercalated Cells (ITCs) in the Mouse Amygdala of Tshz1 Mutants Correlates with Fear, Depression, and Social Interaction Phenotypes

The intercalated cells (ITCs) of the amygdala have been shown to be critical regulatory components of amygdalar circuits, which control appropriate fear responses. Despite this, the molecular processes guiding ITC development remain poorly understood. Here we establish the zinc finger transcription factor Tshz1 as a marker of ITCs during their migration from the dorsal lateral ganglionic eminence through maturity. Using germline and conditional knock-out (cKO) mouse models, we show that Tshz1 is required for the proper migration and differentiation of ITCs. In the absence of Tshz1, migrating ITC precursors fail to settle in their stereotypical locations encapsulating the lateral amygdala and BLA. Furthermore, they display reductions in the ITC marker Foxp2 and ectopic persistence of the dorsal lateral ganglionic eminence marker Sp8. Tshz1 mutant ITCs show increased cell death at postnatal time points, leading to a dramatic reduction by 3 weeks of age. In line with this, Foxp2-null mutants also show a loss of ITCs at postnatal time points, suggesting that Foxp2 may function downstream of Tshz1 in the maintenance of ITCs. Behavioral analysis of male Tshz1 cKOs revealed defects in fear extinction as well as an increase in floating during the forced swim test, indicative of a depression-like phenotype. Moreover, Tshz1 cKOs display significantly impaired social interaction (i.e., increased passivity) regardless of partner genetics. Together, these results suggest that Tshz1 plays a critical role in the development of ITCs and that fear, depression-like and social behavioral deficits arise in their absence.SIGNIFICANCE STATEMENT We show here that the zinc finger transcription factor Tshz1 is expressed during development of the intercalated cells (ITCs) within the mouse amygdala. These neurons have previously been shown to play a crucial role in fear extinction. Tshz1 mouse mutants exhibit severely reduced numbers of ITCs as a result of abnormal migration, differentiation, and survival of these neurons. Furthermore, the loss of ITCs in mouse Tshz1 mutants correlates well with defects in fear extinction as well as the appearance of depression-like and abnormal social interaction behaviors reminiscent of depressive disorders observed in human patients with distal 18q deletions, including the Tshz1 locus.

Central amygdalar nucleus treated with orexin neuropeptides evoke differing feeding and grooming responses in the hamster

Interaction of the orexinergic (ORXergic) neuronal system with the excitatory (glutamate, l-Glu) or the inhibitory (GABA) neurosignaling complexes evokes major homeostatic physiological events. In this study, effects of the two ORXergic neuropeptides (ORX-A/B) on their receptor (ORX-2R) expression changes were correlated to feeding and grooming actions of the hibernating hamster (Mesocricetus auratus). Infusion of the central amygdala nucleus (CeA) with ORX-A caused hamsters to consume notable quantities of food, while ORX-B accounted for a moderate increase. Interestingly the latter neuropeptide was responsible for greater frequencies of grooming with respect to both controls and the hamsters treated with ORX-A. These distinct behavioral changes turned out to be even greater in the presence of l-Glu agonist (NMDA) while the α1 GABAA receptor agonist (zolpidem, Zol) greatly reduced ORX-A-dependent feeding bouts. Moreover, ORX-A+NMDA mainly promoted greater ORX-2R expression levels with respect to ORX-A-treated hamsters while ORX-B+Zol was instead largely responsible for a down-regulatory trend. Overall, these features point to CeA ORX-2R sites as key sensory limbic elements capable of regulating eating and grooming responses, which may provide useful insights regarding the type of molecular mechanism(s) operating during feeding bouts.