Probes for INS

Maternal diabetes is known to adversely influence brain development in offspring. Here, we provide evidence that this involves the circulating metabolite methylglyoxal, which is increased in diabetes, and its detoxifying enzyme, glyoxalase 1 (Glo1), which when mutated is associated with neurodevelopmental disorders. Specifically, when Glo1 levels were decreased in embryonic mouse cortical neural precursor cells (NPCs), this led to premature neurogenesis and NPC depletion embryonically and long-term alterations in cortical neurons postnatally. Increased circulating maternal methylglyoxal caused similar changes in embryonic cortical precursors and neurons and long-lasting changes in cortical neurons and NPCs in adult offspring. Depletion of embryonic and adult NPCs was also observed in murine offspring exposed to a maternal diabetic environment. Thus, the Glo1-methylglyoxal pathway integrates maternal and NPC metabolism to regulate neural development, and perturbations in this pathway lead to long-lasting alterations in adult neurons and NPC pools.

Stress is a precipitating agent in neuropsychiatric disease and initiates relapse to drug-seeking behavior in addicted patients. Targeting the stress system in protracted abstinence from drugs of abuse with anxiolytics may be an effective treatment modality for substance use disorders. α2A-adrenergic receptors (α2A-ARs) in extended amygdala structures play key roles in dampening stress responses. Contrary to early thinking, α2A-ARs are expressed at non-noradrenergic sites in the brain. These non-noradrenergic α2A-ARs play important roles in stress-responses, but their cellular mechanisms of action are unclear. In humans, the α2A-AR agonist guanfacine reduces overall craving and uncouples craving from stress yet minimally affects relapse, potentially due to competing actions in the brain. Here we show that heteroceptor α2A-ARs postsynaptically enhance dorsal BNST (dBNST) neuronal activity in mice of both sexes. This effect is mediated by hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels, as inhibition of these channels is necessary and sufficient for excitatory actions. Finally, this excitatory action is mimicked by clozapine-N-oxide activation of the Gi-coupled DREADD hM4Di in dBNST neurons, and its activation elicits anxiety-like behavior in the elevated plus maze. Together, this data provides a framework for elucidating cell-specific actions of GPCR signaling and provides a potential mechanism whereby competing anxiogenic and anxiolytic actions of guanfacine may affect its clinical utility in the treatment of addiction.SIGNIFICANCE STATEMENTStress impacts the development of neuropsychiatric disorders including anxiety and addiction. Guanfacine is an α2A-adrenergic receptor (α2A-AR) agonist with actions in the bed nucleus of the stria terminalis (BNST) that produces antidepressant actions and uncouples stress from reward-related behaviors. Here we show that guanfacine increases dBNST neuronal activity through actions at postsynaptic α2A-ARs via a mechanism that involves hyperpolarization-activated cyclic nucleotide gated cation (HCN) channels. This action is mimicked by activation of the designer receptor hM4Di expressed in the BNST, which also induces anxiety-like behaviors. Together, these data suggest 1) that postsynaptic α2A-ARs in BNST have excitatory actions on BNST neurons, and 2) these actions can be phenocopied by the so-called "inhibitory" DREADDs, suggesting care must be taken regarding interpretation of data obtained with these tools.

We previously confirmed that postprandial alterations in the circulation and metabolism after a single oral dose of flavan 3-ols (mixture of catechin and catechin oligomers) were involved in an increase in sympathetic nervous activity. However, it is well known that, in response to various stresses, activation of the hypothalamic-pituitary-adrenal (HPA) axis occurs together with sympathetic nerve activity, which is associated with activation of the sympathetic-adrenal-medullary (SAM) axis. In this study, we examined whether the HPA axis was activated after a single dose of flavan 3-ols. We administered an oral dose of 10 or 50 mg/kg flavan 3-ols to male ICR mice, removed the brains, and fixed them in paraformaldehyde-phosphate buffer. Other animals that were treated similarly were decapitated, and blood was collected. In the paraventricular nucleus (PVN), c-fos mRNA expression increased significantly at 15 min after administration of either 10 or 50 mg/kg flavan 3-ols. Corticotropin-releasing hormone (CRH) mRNA expression levels significantly increased at 240 min after administration of 10 mg/kg flavan 3-ols, and at 60 min after administration of 50 mg/kg flavan 3-ols. Plasma corticosterone levels were also significantly increased at 240 min after ingestion of 50 mg/kg flavan 3-ols. In this experiment, we confirmed that the ingestion of flavan 3-ols acted as a stressor in mammals with activation both the SAM and HPA axes.