Fos Induction Research Articles

Neuromedin U Neurons in the Edinger–Westphal Nucleus Respond to Alcohol Without Interfering with the Urocortin 1 Response

The Edinger–Westphal nucleus (EW) is a midbrain nucleus composed of a preganglionic, cholinergic subpopulation and a densely clustered peptidergic subpopulation (EWcp). The EWcp is one of the few brain regions that show consistent induction of FOS following voluntary alcohol intake. Previous results in rodents point to urocortin 1 (UCN1) as one of the peptides most involved in the control of ethanol intake and preference. Notably, the functions described for UCN1, such as reward processing, stress coping or the regulation of feeding behavior are similar to those described for the neuropeptide neuromedin U (NMU). Interestingly, NMU has been recently associated with the modulation of alcohol-related behaviors. However, little is known about the expression and functionality of NMU neurons in alcohol-responsive areas. In this study, we used the recently developed Nmu-Cre knock-in mouse model to examine the expression of NMU in the subaqueductal paramedian zone comprising the EWcp. We delved into the characterization and co-expression of NMU with other markers already described in the EWcp. Moreover, using FOS as a marker of neuronal activity, we tested whether NMU neurons were sensitive to acute alcohol administration. Overall, we provided novel insights on NMU expression and functionality in the EW region. We showed the presence of NMU within a subpopulation of UCN1 neurons in the EWcp and demonstrated that this partial co-expression does not interfere with the responsivity of UCN1-containing cells to alcohol. Moreover, we proposed that the UCN1 content in these neurons may be influenced by sex.

Effect of Short-Term Restraint Stress on the Hypothalamic Transcriptome Profiles of Rats with Inherited Stress-Induced Arterial Hypertension (ISIAH) and Normotensive Wistar Albino Glaxo (WAG) Rats.

Emotional stress is one of the health risk factors in the modern human lifestyle. Stress exposure can provoke the manifestation of various pathological conditions, one of which is a sharp increase in the blood pressure level. In the present study, we analyzed changes in the transcriptome profiles of the hypothalamus of hypertensive ISIAH and normotensive WAG rats exposed to a single short-term restraint stress (the rat was placed in a tight wire-mesh cage for 2 h). This type of stress can be considered emotional stress. The functional annotation of differentially expressed genes allowed us to identify the most significantly altered biological processes in the hypothalamus of hypertensive and normotensive rats. The study made it possible to identify a group of genes that describe a general response to stress, independent of the rat genotype, as well as a hypothalamic response to stress specific to each strain. The alternatively changing expression of the Npas4 (neuronal PAS domain protein 4) gene, which is downregulated in the hypothalamus of the control WAG rats and induced in the hypothalamus of hypertensive ISIAH rats, is suggested to be the key event for understanding inter-strain differences in the hypothalamic response to stress. The stress-dependent ISIAH strain-specific induction of Fos and Jun gene transcription may play a crucial role in neuronal activation in this rat strain. The data obtained can be potentially useful in the selection of molecular targets for the development of pharmacological approaches to the correction of stress-induced pathologies related to neuronal excitability, taking into account the hypertensive status of the patients.

Recruitment of hippocampal and thalamic pathways to the central amygdala in the control of feeding behavior under novelty.

It is adaptive to restrict eating under uncertainty, such as during habituation to novel foods and unfamiliar environments. However, sustained restrictive eating can become maladaptive. Currently, the neural substrates of restrictive eating are poorly understood. Using a model of feeding avoidance under novelty, our recent study identified forebrain activation patterns and found evidence that the central nucleus of the amygdala (CEA) is a core integrating node. The current study analyzed the activity of CEA inputs in male and female rats to determine if specific pathways are recruited during feeding under novelty. Recruitment of direct inputs from the paraventricular nucleus of the thalamus (PVT), the infralimbic cortex (ILA), the agranular insular cortex (AI), the hippocampal ventral field CA1, and the bed nucleus of the stria terminals (BST) was assessed with combined retrograde tract tracing and Fos induction analysis. The study found that during consumption of a novel food in a novel environment, larger number of neurons within the PVTp and the CA1 that send monosynaptic inputs to the CEA were recruited compared to controls that consumed familiar food in a familiar environment. The ILA, AI, and BST inputs to the CEA were similarly recruited across conditions. There were no sex differences in activation of any of the pathways analyzed. These results suggest that the PVTp-CEA and CA1-CEA pathways underlie feeding inhibition during novelty and could be potential sites of malfunction in excessive food avoidance.

Electroacupuncture reduced airway inflammation by activating somatosensory-sympathetic pathways in allergic asthmatic rats.

Electroacupuncture (EA) treatment is efficacious in patients with respiratory disorders, although the mechanisms of its action in lung-function protection are poorly understood. This study aimed to explore the neuroanatomical mechanisms of EA stimulation at the BL13 acupoint (Feishu, EA-BL13) improvement in asthma. Allergic asthma was induced by intranasal 2.0% ovalbumin (OVA) instillation combined with intraperitoneal injection of the 10.0% OVA. The levels of interleukin (IL)-4 and IL-5 were detected by enzyme-linked immunosorbent assay. Hematoxylin and eosin and periodic acid-schiff stain were used to evaluate inflammatory cell infiltration and mucus secretion. Cellular oncogene fos induction in neurons after EA stimulation was detected by immunofluorescent staining. The mRNA expression levels of adrenergic receptors were quantified with real-time polymerase chain reaction. EA improved airway inflammation and mucus secretion mainly by activating somatosensory-sympathetic pathways (P<0.001). Briefly, the intermediolateral (IML) nuclei of the spinal cord received signals from somatic EA stimulation and then delivered the information via the sympathetic trunk to the lung. Excited sympathetic nerve endings in lung tissue released large amounts of catecholamines that specifically activated the β2 adrenergic receptor (β2AR) on T cells (P<0.01) and further decreased the levels of IL-4 and IL-5 (P<0.001) through the cyclic adenosine monophosphate/protein kinase A signaling pathway. This study provided a new explanation and clinical basis for the use of EA-BL13 as a treatment for allergic asthma in both the attack and remission stages and other respiratory disorders related to airway inflammation.

Restraint stress-induced expression of &lt;i&gt;Fos&lt;/i&gt; and several related genes in the hypothalamus of the hypertensive ISIAH rats

Stress can play a significant role in the development of arterial hypertension and many other complications of cardiovascular diseases. Considerable attention is paid to the study of the molecular mechanisms involved in the body’s response to stressful influences, but there are still many blank spots in understanding the details. ISIAH rats model a stress-sensitive form of arterial hypertension. ISIAH rats are characterized by genetically determined enhanced hypothalamic-adrenal-cortical and sympathetic adrenomedullary systems activity, which suggests a functional state of increased stress reactivity. In the present study, for the first time, the time course of the Fos and several related genes’ expression was studied in the hypothalamus of adult male hypertensive ISIAH rats after exposure to a single restraint stress of different duration (30, 60, and 120 minutes). The results of the study showed the activation of Fos transcription with a peak 1 hour after the onset of restraint stress. The dynamics of Fos gene activation coincides with the dynamics of blood pressure increase after stress. Restraint stress also alters the transcription of several other genes encoding transcription factors (Jun, Nr4a3, Jdp2, Ppargc1a) associated with the development of cardiovascular diseases. Since Fos induction is a marker of brain neuron activation, we can conclude that increased stress reactivity of the hypothalamic-pituitary-adrenocortical and sympathoadrenal systems of hypertensive ISIAH rats during short-term restriction is accompanied by activation of hypothalamic neurons and increased blood pressure level.

Restraint Stress-Induced Expression of Fos and Several Related Genes in the Hypothalamus of Hypertensive ISIAH Rats

Stress can play a significant role in arterial hypertension and many other complications of cardiovascular diseases. Considerable attention is paid to the study of the molecular mechanisms involved in the body response to stressful influences, but there are still many blank spots in understanding the details. ISIAH rats model the stress-sensitive form of arterial hypertension. ISIAH rats are characterized by genetically determined enhanced activities of the hypothalamic-pituitary-adrenocortical and sympathetic-adrenomedullary systems, suggesting a functional state of increased stress reactivity. For the first time, the temporal expression patterns of Fos and several related genes were studied in the hypothalamus of adult male hypertensive ISIAH rats after a single exposure to restraint stress for 30, 60, or 120 min. Fos transcription was activated and peaked 1 h after the start of restraint stress. The time course of Fos activation coincided with that of blood pressure increase after stress. Activation of hypothalamic neurons also alters the transcription levels of several transcription factor genes (Jun, Nr4a3, Jdp2, and Ppargc1a), which are associated with the development of cardiovascular diseases. Because Fos induction is a marker of brain neuron activation, activation of hypothalamic neurons and an increase in blood pressure were concluded to accompany increased stress reactivity of the hypothalamic-pituitary-adrenocortical and sympathoadrenal systems in hypertensive ISIAH rats during short-term restraint.

Urban and rural male song sparrows (Melospiza melodia) differ in territorial aggression and activation of vasotocin neurons in response to song challenge

When living in urban habitats, ‘urban adapter’ species often show greater aggression toward conspecifics, yet we do not understand the mechanisms underlying this behavioral shift. The neuroendocrine system regulates socio-sexual behaviors including aggression and thus could mediate behavioral responses to urbanization. Indeed, urban male song sparrows (Melospiza melodia), which are more territorially aggressive, also have greater abundance of the neuropeptide arginine vasotocin (AVT) in nodes of the brain social behavior network. Higher abundance of AVT could reflect long-term synthesis that underlies baseline territoriality or short-term changes that regulate aggression in response to social challenge. To begin to resolve the timeframe over which the AVT system contributes to habitat differences in aggression we used immediate early gene co-expression as a measure of the activation of AVT neurons. We compared Fos induction in AVT-immunoreactive neurons of the bed nucleus of the stria terminalis (BSTm) and paraventricular nucleus of the hypothalamus (PVN) between urban and rural male song sparrows in response to a short (< 5 min.) or long (> 30 min.) song playback to simulate territorial intrusion by another male. We found that urban males had a higher proportion of Fos-positive AVT neurons in both brain regions compared to rural males, regardless of the duration of song playback. Our results suggest that AVT neurons remain activated in urban males, independently of the duration of social challenge. These findings that Fos induction in AVT neurons differs between rural and urban male song sparrows further implicate this system in regulating behavioral responses to urbanization.

PACAP Controls Endocrine and Behavioral Stress Responses via Separate Brain Circuits

BackgroundThe neuropeptide PACAP (pituitary adenylate cyclase-activating polypeptide) is a master regulator of central and peripheral stress responses, yet it is not clear how PACAP projections throughout the brain execute endocrine and behavioral stress responses. MethodsWe used AAV (adeno-associated virus) neuronal tracing, an acute restraint stress (ARS) paradigm, and intersectional genetics, in C57BL/6 mice, to identify PACAP-containing circuits controlling stress-induced behavior and endocrine activation. ResultsPACAP deletion from forebrain excitatory neurons, including a projection directly from medial prefrontal cortex to hypothalamus, impairs c-fos activation and corticotropin-releasing hormone (CRH) messenger RNA elevation in the paraventricular nucleus after 2 hours of restraint, without affecting ARS-induced hypophagia, or c-fos elevation in nonhypothalamic brain. Elimination of PACAP within projections from lateral parabrachial nucleus to extended amygdala, on the other hand, attenuates ARS-induced hypophagia, along with extended amygdala fos induction, without affecting ARS-induced CRH messenger RNA elevation in the paraventricular nucleus. PACAP projections to extended amygdala terminate at protein kinase C delta type (PKCδ) neurons in both the central amygdala and the oval bed nucleus of the stria terminalis. Silencing of PKCδ neurons in the central amygdala, but not in the oval bed nucleus of the stria terminalis, attenuates ARS-induced hypophagia. Experiments were carried out in mice of both sexes with n ≥ 3 per group. ConclusionsA frontocortical descending PACAP projection controls paraventricular nucleus CRH messenger RNA production to maintain hypothalamic-pituitary-adrenal axis activation and regulate the endocrine response to stress. An ascending PACAPergic projection from the external lateral parabrachial nucleus to PKCδ neurons in the central amygdala regulates behavioral responses to stress. Defining two separate limbs of the acute stress response provides broader insight into the specific brain circuitry engaged by the psychogenic stress response.

The Delta-Opioid Receptor Bidirectionally Modulates Itch

Opioid signaling has been shown to be critically important in the neuromodulation of sensory circuits in the superficial spinal cord. Agonists of the mu-opioid receptor (MOR) elicit itch, whereas agonists of the kappa-opioid receptor (KOR) have been shown to inhibit itch. Despite the clear roles of MOR and KOR for the modulation itch, whether the delta-opioid receptor (DOR) is involved in the regulation of itch remained unknown. Here, we show that intrathecal administration of DOR agonists suppresses chemical itch and that intrathecal application of DOR antagonists is sufficient to evoke itch. We identify that spinal enkephalin neurons co-express neuropeptide Y (NPY), a peptide previously implicated in the inhibition of itch. In the spinal cord, DOR overlapped with both the NPY receptor (NPY1R) and KOR, suggesting that DOR neurons represent a site for convergent itch information in the dorsal horn. Lastly, we found that neurons co-expressing DOR and KOR showed significant Fos induction following pruritogen-evoked itch. These results uncover a role for DOR in the modulation of itch in the superficial dorsal horn. PerspectiveThis article reveals the role of the delta-opioid receptor in itch. Intrathecal administration of delta agonists suppresses itch whereas the administration of delta antagonists is sufficient to induce itch. These studies highlight the importance of delta-opioid signaling for the modulation of itch behaviors, which may represent new targets for the management of itch disorders.

Sex differences in activation of extra-hypothalamic forebrain areas during hedonic eating.

Palatable foods can stimulate appetite without hunger, and unconstrained overeating underlies obesity and binge eating disorder. Women are more prone to obesity and binge eating than men but the neural causes of individual differences are unknown. In an animal model of hedonic eating, a prior study found that females were more susceptible than males to eat palatable food when sated and that the neuropeptide orexin/hypocretin (ORX) was crucial in both sexes. The current study examined potential extra-hypothalamic forebrain targets of ORX signaling during hedonic eating. We measured Fos induction in the cortical, thalamic, striatal, and amygdalar areas that receive substantial ORX inputs and contain their receptors in hungry and sated male and female rats during palatable (high-sucrose) food consumption. During the test, hungry rats of both sexes ate substantial amounts, and while sated males ate much less than hungry rats, sated females ate as much as hungry rats. The Fos induction analysis identified sex differences in recruitment of specific areas of the medial prefrontal cortex, paraventricular nucleus of the thalamus (PVT), nucleus accumbens (ACB), and central nucleus of the amygdala (CEA), and similar patterns across sexes in the insular cortex. There was a striking activation of the infralimbic cortex in sated males, who consumed the least amount food and unique correlations between the insular cortex, PVT, and CEA, as well as the prelimbic cortex, ACB, and CEA in sated females but not sated males. The study identified key functional circuits that may drive hedonic eating in a sex-specific manner.

Fos ensembles encode and shape stable spatial maps in the hippocampus

In the hippocampus, spatial maps are formed by place cells while contextual memories are thought to be encoded as engrams1–6. Engrams are typically identified by expression of the immediate early gene Fos, but little is known about the neural activity patterns that drive, and are shaped by, Fos expression in behaving animals7–10. Thus, it is unclear whether Fos-expressing hippocampal neurons also encode spatial maps and whether Fos expression correlates with and affects specific features of the place code11. Here we measured the activity of CA1 neurons with calcium imaging while monitoring Fos induction in mice performing a hippocampus-dependent spatial learning task in virtual reality. We find that neurons with high Fos induction form ensembles of cells with highly correlated activity, exhibit reliable place fields that evenly tile the environment and have more stable tuning across days than nearby non-Fos-induced cells. Comparing neighbouring cells with and without Fos function using a sparse genetic loss-of-function approach, we find that neurons with disrupted Fos function have less reliable activity, decreased spatial selectivity and lower across-day stability. Our results demonstrate that Fos-induced cells contribute to hippocampal place codes by encoding accurate, stable and spatially uniform maps and that Fos itself has a causal role in shaping these place codes. Fos ensembles may therefore link two key aspects of hippocampal function: engrams for contextual memories and place codes that underlie cognitive maps.

157-OR: High-Fat–Diet Feeding Disrupts Thermal Responsiveness of AgRP Neurons

To defend energy homeostasis in the cold requires energy expenditure (to support thermogenesis) and energy intake increase, enabling core temperature to be maintained with no change to body fat stores. When acutely housed at a mild cold (14°C) , mice increase both food intake and heat production rapidly (∼minutes) , and these responses occur in parallel. We hypothesized a role for Agouti-related peptide (AgRP) neurons in this response and find their activity is regulated by thermal sensory input, and they increase activity, measured by Fos induction and fiber photometry, upon cold sensation, and reduce activity as sensed temperatures rise. By inhibiting AgRP neurons during acute cold exposure, we also find this increase in AgRP neuron activity is required for the hyperphagic response to cold. Recent evidence found high-fat diet (HFD) feeding reduced AgRP neuron responsiveness to gastric hormones and standard chow diet presentation, and we hypothesized that their response to thermal input might also be blunted. We find that although 12-week HFD-fed mice exhibit intact thermogenic responses to cold and defend a normal core body temperature, they fail to increase energy intake and consequently experience weight loss not observed in chow-fed controls. This uncoupling of energy intake from energy expenditure is present even after a shorter, 2-week exposure to HFD-feeding, implying a role for diet separate from obesity in the phenotype. Using Agrp-Cre/GFP marker mice, we find acute cold exposure rapidly induces Fos in chow-fed mice, but this response is lacking in HFD-fed mice. This effect correlates with a failure to increase hypothalamic Agrp mRNA even after five days of mild cold exposure. Using photometry to measure AgRP neuron calcium activity, we find activity changes associated with thermal input, both cold and warm, are blunted with HFD feeding. Further testing will determine exactly how the food intake response to cold has become uncoupled from other thermoregulatory responses across the development of obesity. Disclosure J.D.Deem: None. T.P.Doan: None. B.N.Phan: None. K.Ogimoto: None. S.J.W.Hu: None. B.Wu: None. M.W.Schwartz: None. G.J.Morton: Research Support; Novo Nordisk A/S. Funding American Diabetes Association (1-19-PDF-103) ; NIDDK (K01 DK126793) , NIDDK (DK089056) , NIDDK (DK124238) , NIDDK (DK035816) , NIDA (P30 DA048736) , NIDDK (DK035816) , NIDDK (DK17047)

Activation of the Central Medial Thalamic Afferent to the Orbitofrontal Cortex Contributes to Successful Reversal Learning

Stress‐related psychiatric disorders, such as major depressive disorder and anxiety disorders, have cognitive symptoms that are not well‐treated by classical antidepressants and cause major detriments to patients’ quality of life. Reversal learning, a form of cognitive flexibility necessary to adapt to a changing environment, is disrupted in stress‐related psychiatric disorders. The orbitofrontal cortex (OFC) mediates reversal learning, and hyperactivity in the OFC is associated with psychiatric disorders in humans. Using a reward‐based discrimination digging task to assess reversal learning in rodents, we have previously reported that chronic stress impairs reversal learning and that inducing long‐term depression in the mediodorsal thalamus to OFC pathway reverses these deficits. However, the circuit‐level mechanisms underlying reversal learning are not well established. Preliminary data using Fos immunohistochemistry, showed a significant decrease in Fos in the lateral OFC following reversal learning, and a significant increase in Fos induction in the central medial thalamus (CM). Converging evidence from other laboratories indicates the CM inhibits the prefrontal cortex. Therefore, we next tested the hypothesis that input to the OFC from the CM, inhibiting the OFC, contributes to successful reversal learning. We used an adeno‐associated virus to deliver an inhibitory (Gi) DREADD or GFP control construct into the CM under the control of the CaMKII promoter, and implanted guide cannulae into the lateral OFC for administration of the DREADD agonist directly at the DREADD‐expressing terminals from the CM. Animals received microinjections of DREADD agonist clozapine‐N‐oxide (300 µM, i.c.) directly preceding the reversal learning task. Activating the Gi DREADD significantly impaired reversal learning, increasing the number of trials it took animals to make six consecutive correct responses. These results suggest that excitatory input from the CM to the OFC is critical for successful reversal learning, indicating a novel role for the CM in cognitive flexibility. Future experiments will investigate the role of thalamic inputs to the OFC in the effects of stress on reversal learning.

Hierarchy of signaling thresholds downstream of the T cell receptor and the Tec kinase ITK

The strength of peptide:MHC interactions with the T cell receptor (TCR) is correlated with the time to first cell division, the relative scale of the effector cell response, and the graded expression of activation-associated proteins like IRF4. To regulate T cell activation programming, the TCR and the TCR proximal interleukin-2-inducible T cell kinase (ITK) simultaneously trigger many biochemically separate signaling cascades. T cells lacking ITK exhibit selective impairments in effector T cell responses after activation, but under the strongest signaling conditions, ITK activity is dispensable. To gain insight into whether TCR signal strength and ITK activity tune observed graded gene expression through the unequal activation of distinct signaling pathways, we examined Erk1/2 phosphorylation or nuclear factor of activated T cells (NFAT) and nuclear factor (NF)-κB translocation in naïve OT-I CD8+ cell nuclei. We observed the consistent digital activation of NFAT1 and Erk1/2, but NF-κB displayed dynamic, graded activation in response to variation in TCR signal strength, tunable by treatment with an ITK inhibitor. Inhibitor-treated cells showed the dampened induction of AP-1 factors Fos and Fosb, NF-κB response gene transcripts, and survival factor Il2 transcripts. ATAC sequencing analysis also revealed that genomic regions most sensitive to ITK inhibition were enriched for NF-κB and AP-1 motifs. Specific inhibition of NF-κB during peptide stimulation tuned the expression of early gene products like c-Fos. Together, these data indicate a key role for ITK in orchestrating the optimal activation of separate TCR downstream pathways, specifically aiding NF-κB activation. More broadly, we revealed a mechanism by which variations in TCR signal strength can produce patterns of graded gene expression in activated T cells.

An Angiotensin-Responsive Connection from the Lamina Terminalis to the Paraventricular Nucleus of the Hypothalamus Evokes Vasopressin Secretion to Increase Blood Pressure in Mice.

Blood pressure is controlled by endocrine, autonomic, and behavioral responses that maintain blood volume and perfusion pressure at levels optimal for survival. Although it is clear that central angiotensin type 1a receptors (AT1aR; encoded by the Agtr1a gene) influence these processes, the neuronal circuits mediating these effects are incompletely understood. The present studies characterize the structure and function of AT1aR neurons in the lamina terminalis (containing the median preoptic nucleus and organum vasculosum of the lamina terminalis), thereby evaluating their roles in blood pressure control. Using male Agtr1a-Cre mice, neuroanatomical studies reveal that AT1aR neurons in the area are largely glutamatergic and send projections to the paraventricular nucleus of the hypothalamus (PVN) that appear to synapse onto vasopressin-synthesizing neurons. To evaluate the functionality of these lamina terminalis AT1aR neurons, we virally delivered light-sensitive opsins and then optogenetically excited or inhibited the neurons while evaluating cardiovascular parameters or fluid intake. Optogenetic excitation robustly elevated blood pressure, water intake, and sodium intake, while optogenetic inhibition produced the opposite effects. Intriguingly, optogenetic excitation of these AT1aR neurons of the lamina terminalis also resulted in Fos induction in vasopressin neurons within the PVN and supraoptic nucleus. Further, within the PVN, selective optogenetic stimulation of afferents that arise from these lamina terminalis AT1aR neurons induced glutamate release onto magnocellular neurons and was sufficient to increase blood pressure. These cardiovascular effects were attenuated by systemic pretreatment with a vasopressin-1a-receptor antagonist. Collectively, these data indicate that excitation of lamina terminalis AT1aR neurons induces neuroendocrine and behavioral responses that increase blood pressure.SIGNIFICANCE STATEMENT Hypertension is a widespread health problem and risk factor for cardiovascular disease. Although treatments exist, a substantial percentage of patients suffer from "drug-resistant" hypertension, a condition associated with increased activation of brain angiotensin receptors, enhanced sympathetic nervous system activity, and elevated vasopressin levels. The present study highlights a role for angiotensin Type 1a receptor expressing neurons located within the lamina terminalis in regulating endocrine and behavioral responses that are involved in maintaining cardiovascular homeostasis. More specifically, data presented here reveal functional excitatory connections between angiotensin-sensitive neurons in the lamina terminals and vasopressin neurons in the paraventricular nucleus of the hypothalamus, and further indicate that activation of this circuit raises blood pressure. These neurons may be a promising target for antihypertensive therapeutics.

Long-lasting tagging of neurons activated by seizures or cocaine administration in Egr1-CreERT2 transgenic mice.

Permanent tagging of neuronal ensembles activated in specific experimental situations is an important objective to study their properties and adaptations. In the context of learning and memory, these neurons are referred to as engram neurons. Here, we describe and characterize a novel mouse line, Egr1-CreERT2 , which carries a transgene in which the promoter of the immediate early gene Egr1 drives the expression of the CreERT2 recombinase that is only active in the presence of tamoxifen metabolite, 4-hydroxy-tamoxifen (4-OHT). Egr1-CreERT2 mice were crossed with various reporter mice, Cre-dependently expressing a fluorescent protein. Without tamoxifen or 4-OHT, no or few tagged neurons were observed. Epileptic seizures induced by pilocarpine or pentylenetetrazol in the presence of tamoxifen or 4-OHT elicited the persistent tagging of many neurons and some astrocytes in the dentate gyrus of hippocampus, where Egr1 is transiently induced by seizures. One week after cocaine and 4-OHT administration, these mice displayed a higher number of tagged neurons in the dorsal striatum than saline/4-OHT controls, with differences between reporter lines. Cocaine-induced tagging required ERK activation and tagged neurons were more likely than others to exhibit ERK phosphorylation or Fos induction after a second injection. Interestingly neurons tagged in saline-treated mice also had an increased propensity to express Fos, suggesting the existence of highly responsive striatal neurons susceptible to be re-activated by cocaine repeated administration, which may contribute to the behavioral adaptations. Our report validates a novel transgenic mouse model for permanently tagging activated neurons and studying long-term alterations of Egr1-expressing cells.

Hedonic Eating: Sex Differences and Characterization of Orexin Activation and Signaling

Palatable taste can stimulate appetite in the absence of hunger, and individual differences in hedonic eating may be critical to overeating. Women are more prone to obesity and binge eating than men, which warrants comparisons of hedonic versus physiological consumption and the underlying neural substrates in both sexes. The current study examined palatable (high-sugar) food consumption in male and female rats under physiological hunger and satiety, and the role of the neuropeptide orexin/hypocretin (ORX). Across multiple tests, females consistently consumed similar amounts of palatable food regardless of whether they were hungry or sated prior to testing. In contrast, males typically adjusted their consumption according to their hunger/satiety state. This difference was specific to palatable food consumption, as both sexes ate standard chow according to their hunger state. ORX is important in food motivation and reward behaviors. Thus, to begin to determine the neuronal mechanisms of hedonic eating, we examined activation and signaling of ORX neurons. We systematically characterized Fos induction patterns of ORX neurons across the entire rostrocaudal extent of the lateral hypothalamus and found that they were activated by food and by fasting in both sexes. Then, we showed that systemic blockade of ORX receptor 1 signaling with SB-334867 decreased palatable food consumption in hungry and sated rats of both sexes. These results demonstrate sex differences in hedonic eating; increased susceptibility in females to overeat palatable food regardless of hunger state, and that ORX is a critical neuropeptide mechanism of hedonic eating in both sexes.

Induction of AP-1 by YAP/TAZ contributes to cell proliferation and organ growth.

Yes-associated protein (YAP) and its homolog transcriptional coactivator with PDZ-binding motif (TAZ) are key effectors of the Hippo pathway to control cell growth and organ size, of which dysregulation yields to tumorigenesis or hypertrophy. Upon activation, YAP/TAZ translocate into the nucleus and bind to TEAD transcription factors to promote transcriptional programs for proliferation or cell specification. Immediate early genes, represented by AP-1 complex, are rapidly induced and control later-phase transcriptional program to play key roles in tumorigenesis and organ maintenance. Here, we report that YAP/TAZ directly promote FOS transcription that in turn contributes to the biological function of YAP/TAZ. YAP/TAZ bind to the promoter region of FOS to stimulate its transcription. Deletion of YAP/TAZ blocks the induction of immediate early genes in response to mitogenic stimuli. FOS induction contributes to expression of YAP/TAZ downstream target genes. Genetic deletion or chemical inhibition of AP-1 suppresses growth of YAP-driven cancer cells, such as Lats1/2-deficient cancer cells as well as Gαq/11 mutated uveal melanoma. Furthermore, AP-1 inhibition almost completely abrogates the hepatomegaly induced by YAP overexpression. Our findings reveal a feed-forward interplay between immediate early transcription of AP-1 and Hippo pathway function.

Medial preoptic estrogen receptor-beta blunts the estrogen receptor-alpha mediated increases in wheel-running behavior of female rats

Estrogens are believed to enhance rodent voluntary wheel-running through medial preoptic (mPOA) estrogen receptor α (ERα) signaling, with little role attributed to estrogen receptor β (ERβ). Systemic ERβ activation has been shown to mitigate ERα driven increases in wheel-running. Therefore, the present goal was to determine whether ERβ signaling in the mPOA plays a similar modulatory role over ERα. We utilized outbred wild-type (WT) and rats selectively bred for low voluntary running (LVR) behavior to address whether mPOA ERβ signaling blunts ERα driven wheel-running behavior and immediate-early gene (Fos, Zif268, and Homer1) mRNA induction. Further, we addressed baseline mPOA mRNA expressions and circulating 17β-estradiol levels between female WT and LVR rats. Following ovariectomy, WT rats reduced running behavior ∼40 %, with no effect in LVR rats. Intra-medial preoptic injection of the ERα-agonist propylpyrazoletriol (PPT) increased wheel-running ∼3.5-fold in WT rats, while injections of the ERβ-agonist diarylpropionitrile (DPN) or a combination of the two agonists had no effect. Similarly, ERα-agonism (PPT) increased Fos and Homer1 induction ∼3-fold in WT and LVR isolated mPOA neurons, with no effect of the ERβ-agonist DPN alone or in combination with PPT, suggesting medial-preoptic ERβ activity may blunt ERα signaling. LVR rats exhibited higher mPOA mRNA expressions of Esr1, Esr2 and Cyp19a1, lower normalized uterine wet weights and lower 17β-estradiol plasma levels compared to WT, suggesting their low running may be due to low circulating estrogen levels. Collectively, these findings highlight mPOA ERβ as a potential neuro-molecular modulator of the estrogenic control of wheel-running behavior.

Oncostatin M, a muscle-secreted myokine, recovers high-glucose-induced impairment of Akt phosphorylation by Fos induction in hippocampal neuron cells.

Oncostatin M is a muscle-secreted myokine that has various effects on neuronal function, however, the underlying molecular mechanism has been poorly defined. In this study, we showed that Oncostatin M increased the phosphorylation of Akt and ERK, proteins crucial for neuron cell survival and proliferation. Furthermore, Oncostatin M increased the expression of c-Fos, a protein with significant involvement in neuronal cell proliferation and survival, through both Akt and ERK. Oncostatin M also increased intracellular calcium concentrations that act upstream of Akt and ERK. Treatment with Oncostatin M led to the recovery of high-glucose-induced impairment of Akt phosphorylation. Thus, Oncostatin M can protect neuronal cell damage related to high-glucose conditions, showing potential as a therapeutic agent.