Sex differences in corticotropin releasing factor regulation of medial septum-mediated memory formation

Distinct septo-hippocampal cholinergic projections separately mediate stress-induced emotional and cognitive deficits

Patients suffering from chronic stress develop numerous symptoms, including emotional and cognitive deficits. The precise circuit mechanisms underlying different symptoms remain poorly understood. We identified two distinct basal forebrain cholinergic subpopulations in mice projecting to the dorsal hippocampus (dHPC) or ventral hippocampus (vHPC), which exhibited distinct input organizations, electrophysiological characteristics, transcriptomics, and responses to positive and negative valences of stimuli and were critical for cognitive and emotional modulation, respectively. Moreover, chronic stress induced elevated anxiety levels and cognitive deficits in mice, accompanied by enhanced vHPC but suppressed dHPC cholinergic projections. Chemogenetic activation of dHPC or inhibition of vHPC cholinergic projections alleviated stress-induced aberrant behaviors. Furthermore, we identified that the acetylcholinesterase inhibitor donepezil combined with blockade of muscarinic receptor 1-type muscarinic acetylcholine receptors in the vHPC rescued both stress-induced phenotypes. These data illuminated distinct septo-hippocampal cholinergic circuits mediated specific symptoms independently under stress, which may provide promising strategies for circuit-based treating of stress-related psychiatric disorders.

Alterations in hippocampal cholinergic dynamics following CRF infusions into the medial septum of male and female rats

Corticoptropin releasing factor (CRF) is implicated in stress-related physiological and behavioral changes. The septohippocampal pathway regulates hippocampal-dependent mnemonic processes, which are affected in stress-related disorders, and given the abundance of CRF receptors in the medial septum (MS), this pathway is influenced by CRF. Moreover, there are sex differences in the MS sensitivity to CRF and its impact on hippocampal function. However, the mechanisms underlying these associations remain elusive. In the present study, we utilized an in vivo biosensor-based electrochemistry approach to examine the impact of MS CRF infusions on hippocampal cholinergic signaling dynamics in male and female rats. Our results show increased amplitudes of depolarization-evoked phasic cholinergic signals in the hippocampus following MS infusion of CRF at the 3 ng dose as compared to the infusion involving artificial cerebrospinal fluid (aCSF). Moreover, a trend for a sex × infusion interaction indicated larger cholinergic transients in females. On the contrary, intraseptal infusion of a physiologically high dose (100 ng) of CRF produced a subsequent reduction in phasic cholinergic transients in both males and females. The assessment of tonic cholinergic activity over 30 min post-infusion revealed no changes at the 3 ng CRF dose in either sex, but a significant infusion × sex interaction indicated a reduction in females at the 100 ng dose of CRF as compared to the aCSF. Taken together, our results show differential, dose-dependent modulatory effects of MS CRF on the dynamics of phasic and tonic modes of cholinergic signaling in the hippocampus of male and female rats. These cholinergic signaling modes are critical for memory encoding and maintaining arousal states, and may underlie sex differences in cognitive vulnerability to stress and stress-related psychiatric disorders.

Septohippocampal cholinergic system at the intersection of stress and cognition: Current trends and translational implications

Deficits in hippocampus-dependent memory processes are common across psychiatric and neurodegenerative disorders such as depression, anxiety and Alzheimer's disease. Moreover, stress is a major environmental risk factor for these pathologies and it exerts detrimental effects on hippocampal functioning via the activation of hypothalamic-pituitary-adrenal (HPA) axis. The medial septum cholinergic neurons extensively innervate the hippocampus. Although, the cholinergic septohippocampal pathway (SHP) has long been implicated in learning and memory, its involvement in mediating the adaptive and maladaptive impact of stress on mnemonic processes remains less clear. Here, we discuss current research highlighting the contributions of cholinergic SHP in modulating memory encoding, consolidation and retrieval. Then, we present evidence supporting the view that neurobiological interactions between HPA axis stress response and cholinergic signalling impact hippocampal computations. Finally, we critically discuss potential challenges and opportunities to target cholinergic SHP as a therapeutic strategy to improve cognitive impairments in stress-related disorders. We argue that such efforts should consider recent conceptualisations on the dynamic nature of cholinergic signalling in modulating distinct subcomponents of memory and its interactions with cellular substrates that regulate the adaptive stress response.

Intermittent fasting disrupts hippocampal-dependent memory and norepinephrine content in aged male and female mice

Intermittent fasting (IMF) is associated with many health benefits in animals and humans. Yet, little is known if an IMF diet affects mood and cognitive processing. We have previously identified that IMF in diet-induced obese males increases norepinephrine and dopamine content in the hypothalamus and increases arcuate neuropeptide Y (NPY) gene expression more than in ad libitum control males. This suggests that IMF may improve cognition through activation of the hindbrain norepinephrine neuronal network and reverse the age-dependent decline in NPY expression. Less is known about the association between anxiety and IMF. Although, in humans, IMF during Ramadan may alleviate anxiety. Here, we address the impact of IMF on anxiety-like behavior using the open field test, hippocampal-dependent memory using the Y-maze and spatial object recognition, and hippocampal-independent memory using novel object recognition in middle-aged male and female (12 mo) and aged male and female (18 mo) mice. Using ELISA, we determined norepinephrine (NE) content in the dorsal hippocampus (DH) and prefrontal cortex (PFC). We also investigated gene expression in the arcuate nucleus (ARC), the lateral hypothalamus (LH), and the locus coeruleus (LC). In IMF-treated females at both ages, we observed an improvement in spatial navigation although an impairment in spatial object orientation. IMF-treated females (12 mo) had a reduction and IMF-treated males (12 mo) displayed an improvement in novel object recognition memory. IMF-treated females (18 mo) exhibited anxiolytic-like behavior and increased locomotion. In the DH, IMF-treated males (12 mo) had a greater amount of NE content and IMF-treated males (18 mo) had a reduction. In the ARC, IMF-treated males (12 mo) exhibited an increase in Agrp and Npy and a decrease in Adr1a. In the ARC, IMF-treated males (18 mo) exhibited an increase in Npy and a decrease in Adr1a; females had a trending decrease in Cart. In the LH at 12 months, IMF-treated males had a decrease in Npy5r, Adr1a, and Adr1b; both males and females had a reduction in Npy1r. In the LH, IMF-treated females (18 mo) had a decrease in Hcrt. In the LC at both ages, mice largely exhibited sex effects. Our findings indicate that IMF produces alterations in mood, cognition, DH NE content, and ARC, LH, and LC gene expression depending on sex and age.

Sex Differences in Stress Response: Classical Mechanisms and Beyond

Neuropsychiatric disorders, which are associated with stress hormone dysregulation, occur at different rates in men and women. Moreover, nowadays, preclinical and clinical evidence demonstrates that sex and gender can lead to differences in stress responses that predispose males and females to different expressions of similar pathologies. In this curated review, we focus on what is known about sex differences in classic mechanisms of stress response, such as glucocorticoid hormones and corticotrophin-releasing factor (CRF), which are components of the hypothalamicpituitary- adrenal (HPA) axis. Then, we present sex differences in neurotransmitter levels, such as serotonin, dopamine, glutamate and GABA, as well as indices of neurodegeneration, such as amyloid β and Tau. Gonadal hormone effects, such as estrogens and testosterone, are also discussed throughout the review. We also review in detail preclinical data investigating sex differences caused by recentlyrecognized regulators of stress and disease, such as the immune system, genetic and epigenetic mechanisms, as well neurosteroids. Finally, we discuss how understanding sex differences in stress responses, as well as in pharmacology, can be leveraged into novel, more efficacious therapeutics for all. Based on the supporting evidence, it is obvious that incorporating sex as a biological variable into preclinical research is imperative for the understanding and treatment of stress-related neuropsychiatric disorders, such as depression, anxiety and Alzheimer's disease.

Coconut Oil Saturated Fatty Acids Improved Energy Homeostasis but not Blood Pressure or Cognition in VCD-Treated Female Mice

Obesity, cardiometabolic disease, cognitive decline, and osteoporosis are symptoms of postmenopause, which can be modeled using 4-vinylcyclohexene diepoxide (VCD)-treated mice to induce ovarian failure and estrogen deficiency combined with high-fat diet (HFD) feeding. The trend of replacing saturated fatty acids (SFAs), for example coconut oil, with seed oils that are high in polyunsaturated fatty acids, specifically linoleic acid (LA), may induce inflammation and gut dysbiosis, and worsen symptoms of estrogen deficiency. To investigate this hypothesis, vehicle (Veh)- or VCD-treated C57BL/6J mice were fed a HFD (45% kcal fat) with a high LA:SFA ratio (22.5%: 8%), referred to as the 22.5% LA diet, or a HFD with a low LA:SFA ratio (1%: 31%), referred to as 1% LA diet, for a period of 23 to 25 weeks. Compared with VCD-treated mice fed the 22.5% LA diet, VCD-treated mice fed the 1% LA diet showed lower weight gain and improved glucose tolerance. However, VCD-treated mice fed the 1% LA diet had higher blood pressure and showed evidence of spatial cognitive impairment. Mice fed the 1% LA or 22.5% LA diets showed gut microbial taxa changes that have been associated with a mix of both beneficial and unfavorable cognitive and metabolic phenotypes. Overall, these data suggest that consuming different types of dietary fat from a variety of sources, without overemphasis on any particular type, is the optimal approach for promoting metabolic health regardless of estrogen status.

Activation of pallidal H2 receptors induces catalepsy in Wistar rats: A regulatory role of CRF1 receptors

An increased concentration of histamine was found in the globus pallidus of parkinsonian patients. The role of this abnormality in the development of parkinsonism is unclear. We examined cataleptogenic activity of histamine injected into the globus pallidus (GP); also, the role of H2 receptors in histamine effect was evaluated. Given a possible role of the GP in integration and processing of stress signals, we tested the involvement of CRF1 receptors in the regulation of histamine effect. The experiments were conducted with male Wistar rats, catalepsy was assessed using bar test. The entopeduncular nucleus (EPN) was used as a neuroanatomical control. Intrapallidal injections of histamine (1.0 and 10.0 µg) produced clear cataleptic response whereas intra-EPN injections were ineffective. Histamine-induced catalepsy was dose-dependently attenuated by H2 receptor antagonist ranitidine and CRF1 receptor antagonist NBI 35965. The results suggest the involvement of pallidal H2 and CRF1 receptors in the development of catalepsy in rats. These findings may provide novel insight into the mechanism of parkinsonian-like disorders. In light of the presented data, H2 and CRF1 receptors might be potential targets for therapy of parkinsonism.

Basolateral amygdala corticotropin-releasing factor receptor type 1 regulates context-cocaine memory strength during reconsolidation in a sex-dependent manner

The basolateral amygdala (BLA) is a critical brain region for cocaine-memory reconsolidation. Corticotropin-releasing factor receptor type 1 (CRFR1) is densely expressed in the BLA, and CRFR1 stimulation can activate intra-cellular signaling cascades that mediate memory reconsolidation. Hence, we tested the hypothesis that BLA CRFR1 stimulation is necessary and sufficient for cocaine-memory reconsolidation. Using an instrumental model of drug relapse, male and female Sprague-Dawley rats received cocaine self-administration training in a distinct environmental context over 10 days followed by extinction training in a different context over 7 days. Next, rats were re-exposed to the cocaine-paired context for 15 min to initiate cocaine-memory retrieval and destabilization. Immediately or 6 h after this session, the rats received bilateral vehicle, antalarmin (CRFR1 antagonist; 500 ng/hemisphere), or corticotropin-releasing factor (CRF; 0.2, 30 or 500 ng/hemisphere) infusions into the BLA. Resulting changes in drug context-induced cocaine seeking (index of context-cocaine memory strength) were assessed three days later. Female rats self-administered more cocaine infusions and exhibited more extinction responding than males. Intra-BLA antalarmin treatment immediately after memory retrieval (i.e., when cocaine memories were labile), but not 6 h later (i.e., after memory reconsolidation), attenuated drug context-induced cocaine seeking at test independent of sex, relative to vehicle. Conversely, intra-BLA CRF treatment increased this behavior selectively in females, in a U-shaped dose-dependent fashion. In control experiments, a high (behaviorally ineffective) dose of CRF treatment did not reduce BLA CRFR1 cell-surface expression in females. Thus, BLA CRFR1 signaling is necessary and sufficient, in a sex-dependent manner, for regulating cocaine-memory strength.

Corticotropin Releasing Factor Binding Protein as a Novel Target to Restore Brain Homeostasis: Lessons Learned From Alcohol Use Disorder Research

Stress is well-known to contribute to the development of many psychiatric illnesses including alcohol and substance use disorder (AUD and SUD). The deleterious effects of stress have also been implicated in the acceleration of biological age, and age-related neurodegenerative disease. The physio-pathology of stress is regulated by the corticotropin-releasing factor (CRF) system, the upstream component of the hypothalamic-pituitary-adrenal (HPA) axis. Extensive literature has shown that dysregulation of the CRF neuroendocrine system contributes to escalation of alcohol consumption and, similarly, chronic alcohol consumption contributes to disruption of the stress system. The CRF system also represents the central switchboard for regulating homeostasis, and more recent studies have found that stress and aberrations in the CRF pathway are implicated in accelerated aging and age-related neurodegenerative disease. Corticotropin releasing factor binding protein (CRFBP) is a secreted glycoprotein distributed in peripheral tissues and in specific brain regions. It neutralizes the effects of CRF by sequestering free CRF, but may also possess excitatory function by interacting with CRF receptors. CRFBP's dual role in influencing CRF bioavailability and CRF receptor signaling has been shown to have a major part in the HPA axis response. Therefore, CRFBP may represent a valuable target to treat stress-related illness, including: development of novel medications to treat AUD and restore homeostasis in the aging brain. This narrative review focuses on molecular mechanisms related to the role of CRFBP in the progression of addictive and psychiatric disorders, biological aging, and age-related neurodegenerative disease. We provide an overview of recent studies investigating modulation of this pathway as a potential therapeutic target for AUD and age-related neurodegenerative disease.

Sex differences in association between cognitive impairment and clinical correlates in Chinese patients with first-episode drug-naïve schizophrenia

BACKGROUND

Schizophrenia is a complex mental illness with significant sex differences. Cognitive impairment is common in patients with schizophrenia, even in remission. This study was designed to examine the sex differences in the relationship between cognitive impairment and clinical correlations with first-episode drug-naïve (FEDN) schizophrenia.

METHODS

93 FEDN patients (male/female = 45/48) and 160 controls (male/female = 74/86) were enrolled to compare the sex differences in cognitive functions measured by the MATRICS Consensus Cognitive Battery (MCCB). Positive and Negative Syndrome Scale (PANSS) and Hamilton Depression Scale (HAMD) were used to evaluate patients' clinical symptoms. We compared cognitive impairment with sociodemographic characteristics and measures of different genders, as well as group-by-sex interactions.

RESULTS

Our results showed that male patients had significantly lower scores for symbol coding, digital sequence, and verbal learning than female patients, while the healthy controls showed similar sex differences. In female patients, multiple linear regression analysis confirmed that PANSS negative symptoms and general psychopathology scores, HAMD total score, and education level were independent contributors to MCCB total score. In male patients, only education was an independent contributor to MCCB total score.

CONCLUSIONS

These findings revealed significant sex differences in cognitive impairments and clinical symptoms in FEDN, which will be worthy of a follow-up study of schizophrenia in the future.

Methyl-CpG binding protein 2 dysfunction provides stress vulnerability with sex- and zygosity-dependent outcomes

Stress vulnerability is a critical factor for the development of trauma-related disorders; however, its biological underpinnings are not clear. We demonstrated that dysfunctions in the X-linked epigenetic factor methyl-CpG binding protein 2 (MeCP2) provide trauma vulnerability in male mice. Given the prominent role of sex in stress outcomes, we explored the effects of MeCP2 hypofunctionality in females. Female mice carrying truncated MeCP2 (heterozygous and homozygous) and wild type controls (wt) were tested for fear memory. Stress-induced corticosterone release and brain expression of hypothalamic-pituitary-adrenal (HPA) axis regulatory genes were also evaluated in wt and mutant mice of both sexes. Although heterozygous females displayed a normal stress-related behavioural profile, homozygous mice showed enhanced memory recall for the threatening context compared to wt, thus recapitulating the phenotype previously evidenced in hemizygous males. Interestingly, MeCP2 truncation abolished the sex differences in stress-induced corticosterone release, which was found increased in mutant males, whereas blunted in mutant females in a zygosity-independent manner. Although heterozygous mice did not differ from controls, homozygous females and hemizygous males showed increased hypotalamic Crh and Avp mRNAs and a differentially altered expression of Fkbp5 in cortical areas. Present results demonstrate that in female mice carrying truncated MeCP2, altered stress responsivity is driven by homozygosity, whereas heterozygosity does not lead to maladaptive stress outcomes. MeCP2 dysfunctions thus provide stress vulnerability in mice with sex- and zygosity-dependent outcomes.

An Analysis of Five TrkB Gene Polymorphisms in Schizophrenia and the Interaction of Its Haplotype with rs6265 BDNF Gene Polymorphism

Aim

The BDNF dysfunction in the schizophrenia has been soundly documented. The TrkB gene is a high-affinity receptor of the BDNF that is changed in schizophrenia and mood disorders. The study had two aims: first, to identify whether the five nucleotide polymorphisms (SNPs) in TrkB gene are associated with a diagnosis of schizophrenia; and the latter, if any association exists between the TrkB SNPs and psychopathology, suicide attempts, and family history of schizophrenia in a Caucasian population.

Methods

Case-control study (401 patients and 657 healthy controls) was used to examine a predisposition for schizophrenia. The tests for psychopathology, suicide attempts, and family history of schizophrenia were conducted only in patient group. The severity of the schizophrenia was measured using the five-factor model of the PANSS. In addition, the haplotype analysis for both the separate for SNPs of TrkB gene and in combination with the rs6265 SNP BDNF gene was conducted.

Results

Our case-control study revealed that the genetic variants of rs10868235 (T/T polymorphic genotype) and rs1387923 (G/G polymorphic genotype) of the TrkB gene were associated with a higher risk of developing schizophrenia in men. However, the A/A wild genotype of rs1387923 was connected with a lower risk for both the development of and the family manifestation of schizophrenia in men. The G polymorphic allele of rs1565445 was associated with an increased risk of suicide in schizophrenia. The tested SNPs of the TrkB gene did not modulate the psychopathology of schizophrenia. The haplotype that was built with five SNPs in the TrkB gene was protective for men, but after joining the rs6265 SNP of the BDNF gene, a haplotype that was protective for women was created.

Corticotropin-Releasing Factor (CRF) circuit modulation of cognition and motivation

The neuropeptide, corticotropin-releasing factor (CRF), is a key modulator of physiological, endocrine, and behavioral responses during stress. Dysfunction of the CRF system has been observed in stress-related affective disorders including post-traumatic stress disorder, depression, and anxiety. Beyond affective symptoms, these disorders are also characterized by impaired cognition, for which current pharmacological treatments are lacking. Thus, there is a need for pro-cognitive treatments to improve quality of life for individuals suffering from mental illness. In this review, we highlight research demonstrating that CRF elicits potent modulatory effects on higher-order cognition via actions within the prefrontal cortex and subcortical monoaminergic and cholinergic systems. Additionally, we identify questions for future preclinical research on this topic, such as the need to investigate sex differences in the cognitive and microcircuit actions of CRF, and whether CRF may represent a pharmacological target to treat cognitive dysfunction. Addressing these questions will provide new insight into pathophysiology underlying cognitive dysfunction and may lead to improved treatments for neuropsychiatric disorders.