Synthesis and Structure-Activity Relationships of 2,5-Dimethoxy-4-Substituted Phenethylamines and the Discovery of CYB210010: A Potent, Orally Bioavailable and Long-Acting Serotonin 5-HT2 Receptor Agonist.

Structure-activity studies of 4-substituted-2,5-dimethoxyphenethylamines led to the discovery of 2,5-dimethoxy-4-thiotrifluoromethylphenethylamines, including CYB210010, a potent and long-acting serotonin 5-HT2 receptor agonist. CYB210010 exhibited high agonist potency at 5-HT2A and 5-HT2C receptors, modest selectivity over 5-HT2B, 5-HT1A, 5-HT6, and adrenergic α2A receptors, and lacked activity at monoamine transporters and over 70 other proteins. CYB210010 (0.1-3 mg/kg) elicited a head-twitch response (HTR) and could be administered subchronically at threshold doses without behavioral tolerance. CYB210010 was orally bioavailable in three species, readily and preferentially crossed into the CNS, engaged frontal cortex 5-HT2A receptors, and increased the expression of genes involved in neuroplasticity in the frontal cortex. CYB210010 represents a new tool molecule for investigating the therapeutic potential of 5-HT2 receptor activation. In addition, several other compounds with high 5-HT2A receptor potency, yet with little or no HTR activity, were discovered, providing the groundwork for the development of nonpsychedelic 5-HT2A receptor ligands.

Microbiome depletion prior to repeat mild TBI differentially alters social deficits and prefrontal cortex plasticity in adolescent and adult rats.

Although aging, repeat mild traumatic brain injury (RmTBI), and microbiome modifications independently change social behavior, there has been no investigation into their cumulative effects on social behavior and neuroplasticity within the prefrontal cortex. Therefore, we examined how microbiome depletion prior to RmTBI affected social behavior and neuroplasticity in adolescent and adult rats. Play, temperament analysis, elevated plus maze, and the hot/cold plate assessed socio-emotional function. Analyses of perineuronal nets (PNNs) and parvalbumin (PV) interneurons was completed. Social-emotional deficits were more pronounced in adults, with microbiome depletion attenuating social behavior deficits associated with RmTBI in both age groups. Microbiome depletion increased branch length and PNN arborization within the PFC but decreased the overall number of PNNs. Adults and males were more vulnerable to RmTBI. Interestingly, microbiome depletion may have attenuated the changes to neuroplasticity and subsequent social deficits, suggesting that the microbiome is a viable, but age-specific, target for RmTBI therapeutics.

Continuous cholinergic-dopaminergic updating in the nucleus accumbens underlies approaches to reward-predicting cues.

The ability to learn Pavlovian associations from environmental cues predicting positive outcomes is critical for survival, motivating adaptive behaviours. This cued-motivated behaviour depends on the nucleus accumbens (NAc). NAc output activity mediated by spiny projecting neurons (SPNs) is regulated by dopamine, but also by cholinergic interneurons (CINs), which can release acetylcholine and glutamate via the activity of the vesicular acetylcholine transporter (VAChT) or the vesicular glutamate transporter (VGLUT3), respectively. Here we investigated behavioural and neurochemical changes in mice performing a touchscreen Pavlovian approach task by recording dopamine, acetylcholine, and calcium dynamics from D1- and D2-SPNs using fibre photometry in control, VAChT or VGLUT3 mutant mice to understand how these signals cooperate in the service of approach behaviours toward reward-predicting cues. We reveal that NAc acetylcholine-dopaminergic signalling is continuously updated to regulate striatal output underlying the acquisition of Pavlovian approach learning toward reward-predicting cues.

Cortical Gyrification Morphology in Adult Males with Mild Traumatic Brain Injury.

Cortical gyrification, as a specific measure derived from magnetic resonance imaging, remains understudied in mild traumatic brain injury (mTBI). Local gyrification index (lGI) and mean curvature are related measures indexing the patterned folding of the cortex,ml which reflect distinct properties of cortical morphology and geometry. Using both metrics, we examined cortical gyrification morphology in 59 adult males with mTBI (n = 29) versus those without (n = 30) mTBI in the subacute phase of injury (between 2 weeks and 3 months). The effect of IQ on lGI and brain-symptom relations were also examined. General linear models revealed greater lGI in mTBI versus controls in the frontal lobes bilaterally, but reduced lGI in mTBI of the left temporal lobe. An age-related decrease in lGI was found in numerous areas, with no significant group-by-age interaction effects observed. Including other factors (i.e., mTBI severity, symptoms, and IQ) in the lGI model yielded similar results with few exceptions. Mean curvature analyses depicted a significant group-by-age interaction with the absence of significant main effects of group or age. Our results suggest that cortical gyrification morphology is adversely affected by mTBI in both frontal and temporal lobes, which are thought of as highly susceptible regions to mTBI. These findings contribute to understanding the effects of mTBI on neuromorphological properties, such as alterations in cortical gyrification, which reflect underlying microstructural changes (i.e., apoptosis, neuronal number, or white matter alterations). Future studies are needed to infer causal relationships between micro- and macrostructural changes after an mTBI and investigate potential sex differences.

Metabolic hormones mediate cognition.

Recent biochemical and behavioural evidence indicates that metabolic hormones not only regulate energy intake and nutrient content, but also modulate plasticity and cognition in the central nervous system. Disruptions in metabolic hormone signalling may provide a link between metabolic syndromes like obesity and diabetes, and cognitive impairment. For example, altered metabolic homeostasis in obesity is a strong determinant of the severity of age-related cognitive decline and neurodegenerative disease. Here we review the evidence that eating behaviours and metabolic hormones-particularly ghrelin, leptin, and insulin-are key players in the delicate regulation of neural plasticity and cognition. Caloric restriction and antidiabetic therapies, both of which affect metabolic hormone levels can restore metabolic homeostasis and enhance cognitive function. Thus, metabolic hormone pathways provide a promising target for the treatment of cognitive decline.

Nutrition, anxiety and hormones. Why sex differences matter in the link between obesity and behavior.

Obesity and mood disorders are two of the most serious health issues of modern times. These health conditions are often linked, with obesity acting both as a cause and consequence of anxiety and depression. Although sex differences in the relationship between obesity and mood disorders are observed in clinical populations, the relative influence of biology versus societal conditioning is unclear. In part, this is because sex effects are rarely examined in the animal models used to derive our understanding of basic biological mechanisms. Due to the perceived confounding nature of hormonal fluctuations in females, rodent studies examining nutritional effects on behavioral responses are typically restricted to males. Yet, hormones play an important role in mediating effects of diet on behavior. In this mini-review, we outline interactions between obesity, hormones and the brain to illustrate the importance of considering sex-specific effects in studies of nutritional effects on behavior. We highlight the need for a more nuanced understanding of how dietary factors influence these relationships, arguing that such knowledge will help improve clinical health outcomes in the management of both obesity and mood disorders.

Functional dissociation of behavioral effects from acetylcholine and glutamate released from cholinergic striatal interneurons.

In the striatum, cholinergic interneurons (CINs) have the ability to release both acetylcholine and glutamate, due to the expression of the vesicular acetylcholine transporter (VAChT) and the vesicular glutamate transporter 3 (VGLUT3). However, the relationship these neurotransmitters have in the regulation of behavior is not fully understood. Here we used reward-based touchscreen tests in mice to assess the individual and combined contributions of acetylcholine/glutamate co-transmission in behavior. We found that reduced levels of the VAChT from CINs negatively impacted dopamine signalling in response to reward, and disrupted complex responses in a sequential chain of events. In contrast, diminished VGLUT3 levels had somewhat opposite effects. When mutant mice were treated with haloperidol in a cue-based task, the drug did not affect the performance of VAChT mutant mice, whereas VGLUT3 mutant mice were highly sensitive to haloperidol. In mice where both vesicular transporters were deleted from CINs, we observed altered reward-evoked dopaminergic signalling and behavioral deficits that resemble, but were worse, than those in mice with specific loss of VAChT alone. These results demonstrate that the ability to secrete two different neurotransmitters allows CINs to exert complex modulation of a wide range of behaviors.

Synchronizing our clocks as we age: the influence of the brain-gut-immune axis on the sleep-wake cycle across the lifespan.

The microbes that colonize the small and large intestines, known as the gut microbiome, play an integral role in optimal brain development and function. The gut microbiome is a vital component of the bidirectional communication pathway between the brain, immune system, and gut, also known as the brain-gut-immune axis. To date, there has been minimal investigation into the implications of improper development of the gut microbiome and the brain-gut-immune axis on the sleep-wake cycle, particularly during sensitive periods of physical and neurological development, such as childhood, adolescence, and senescence. Therefore, this review will explore the current literature surrounding the overlapping developmental periods of the gut microbiome, brain, and immune system from birth through to senescence, while highlighting how the brain-gut-immune axis affects the maturation and organization of the sleep-wake cycle. We also examine how a dysfunction to either the microbiome or the sleep-wake cycle negatively affects the bidirectional relationship between the brain and gut, and subsequently the overall health and functionality of this complex system. Additionally, this review integrates therapeutic studies to demonstrate when dietary manipulations, such as supplementation with probiotics and prebiotics, can modulate the gut microbiome to enhance the health of the brain-gut-immune axis and optimize our sleep-wake cycle.

Intergenerational effects of a paternal Western diet during adolescence on offspring gut microbiota, stress reactivity, and social behavior.

The global consumption of highly processed, calorie-dense foods has contributed to an epidemic of overweight and obesity, along with negative consequences for metabolic dysfunction and disease susceptibility. As it becomes apparent that overweight and obesity have ripple effects through generations, understanding of the processes involved is required, in both maternal and paternal epigenetic inheritance. We focused on the patrilineal effects of a Western-style high-fat (21%) and high-sugar (34%) diet (WD) compared to control diet (CD) during adolescence and investigated F0 and F1 mice for physiological and behavioral changes. F0 males (fathers) showed increased body weight, impaired glycemic control, and decreased attractiveness to females. Paternal WD caused significant phenotypic changes in F1 offspring, including higher body weights of pups, increased Actinobacteria abundance in the gut microbiota (ascertained using 16S microbiome profiling), a food preference for WD pellets, increased male dominance and attractiveness to females, as well as decreased behavioral despair. These results collectively demonstrate the long-term intergenerational effects of a Western-style diet during paternal adolescence. The behavioral and physiological alterations in F1 offspring provide evidence of adaptive paternal programming via epigenetic inheritance. These findings have important implications for understanding paternally mediated intergenerational inheritance, and its relevance to offspring health and disease susceptibility.

The spontaneous location recognition task for assessing spatial pattern separation and memory across a delay in rats and mice.

Keeping similar memories distinct from one another is a critical cognitive process without which we would have difficulty functioning in everyday life. Memories are thought to be kept distinct through the computational mechanism of pattern separation, which reduces overlap between similar input patterns to amplify differences among stored representations. At the behavioral level, impaired pattern separation has been shown to contribute to memory deficits seen in neuropsychiatric and neurodegenerative diseases, including Alzheimer's disease, and in normal aging. This protocol describes the use of the spontaneous location recognition (SLR) task in mice and rats to behaviorally assess spatial pattern separation ability. This two-phase spontaneous memory task assesses the extent to which animals can discriminate and remember object locations presented during the encoding phase. Using three configurations of the task, the similarity of the to-be-remembered locations can be parametrically manipulated by altering the spatial positions of objects-dissimilar, similar or extra similar-to vary the load on pattern separation. Unlike other pattern separation tasks, SLR varies the load on pattern separation during encoding, when pattern separation is thought to occur. Furthermore, SLR can be used in standard rodent behavioral facilities with basic expertise in rodent handling. The entire protocol takes ~20 d from habituation to testing of the animals on all three task configurations. By incorporating breaks between testing, and varying the objects used as landmarks, animals can be tested repeatedly, increasing experimental power by allowing for within-subjects manipulations.

Of 'junk food' and 'brain food': how parental diet influences offspring neurobiology and behaviour.

Unhealthy lifestyles and mental health problems are increasingly prevalent globally. Not only are 'junk food'-induced overweight and obesity risk factors for the development of brain disorders but they are also associated intergenerationally with ill health. Here, we reflect on the current knowledge of how maternal and paternal diet influences offspring brain development and behaviour, potentially predisposing children to mental health problems. Mounting evidence indicates diet-induced maternal and paternal programming of infant metabolism and neurobehavioural function, with potential downstream effects on mental health and resilience. Beyond the central nervous system (CNS), the microbiota-gut-brain axis has emerged as an important mediator of host physiology. We discuss how intergenerational seeding of the gut microbiome via parental lineage can influence offspring gut health and neurobiology.

Age-dependent and region-specific alteration of parvalbumin neurons, perineuronal nets and microglia in the mouse prefrontal cortex and hippocampus following obesogenic diet consumption.

Emergent evidence demonstrates that excessive consumption of high fat and high sugar (HFHS) diets has negative consequences on hippocampal and prefrontal cortex (PFC) function. Moreover, the delayed maturation of the PFC including the late development of parvalbumin-expressing (PV) interneurons and perineuronal nets (PNNs) may promote vulnerability to HFHS diet-induced nutritional stress. However, the young brain may have some resistance to diet-induced neuroinflammation. Thus, we examined the impact of a HFHS diet commencing either in adolescence or adulthood in male mice. PV interneurons, PNNs and microglia were assessed using immunohistochemistry. We observed greater numbers of PV neurons and PNNs in the hippocampus and the prelimbic and infralimbic PFC in adult mice in comparison to our younger cohort. Mice that consumed HFHS diet as adults had reduced numbers of hippocampal PV neurons and PNNs, which correlated with adiposity. However, we saw no effects of diet on PV and PNNs in the PFC. HFHS diet increased microgliosis in the adult cohort, and morphological changes to microglia were observed in the PFC and hippocampus of the adolescent cohort, with a shift to activated microglia phenotypes. Taken together, these findings demonstrate different regional and age-specific effects of obesogenic diets on PV neurons, PNNs and microglia.

Hippocampal neurogenesis and memory in adolescence following intrauterine growth restriction.

Intrauterine growth restriction (IUGR) is associated with hippocampal alterations that can increase the risk of short-term memory impairments later in life. Despite the role of hippocampal neurogenesis in learning and memory, research into the long-lasting impact of IUGR on these processes is limited. We aimed to determine the effects of IUGR on neuronal proliferation, differentiation and morphology, and on memory function at adolescent equivalent age. At embryonic day (E) 18 (term ∼E22), placental insufficiency was induced in pregnant Wistar rats via bilateral uterine vessel ligation to generate IUGR offspring (n = 10); control offspring (n = 11) were generated via sham surgery. From postnatal day (P) 36-44, spontaneous location recognition (SLR), novel object location and recognition (NOL, NOR), and open field tests were performed. Brains were collected at P45 to assess neurogenesis (immunohistochemistry), dendritic morphology (Golgi staining), and brain-derived neurotrophic factor expression (BDNF; Western blot analysis). In IUGR versus control rats there was no difference in object preference in the NOL or NOR, the similar and dissimilar condition of the SLR task, or in locomotion and anxiety-like behavior in the open field. There was a significant increase in the linear density of immature neurons (DCX+) in the subgranular zone (SGZ) of the dentate gyrus (DG), but no difference in the linear density of proliferating cells (Ki67+) in the SGZ, nor in areal density of mature neurons (NeuN+) or microglia (Iba-1+) in the DG in IUGR rats compared to controls. Dendritic morphology of dentate granule cells did not differ between groups. Protein expression of the BDNF precursor (pro-BDNF), but not mature BDNF, was increased in the hippocampus of IUGR compared with control rats. These findings highlight that while the long-lasting prenatal hypoxic environment may impact brain development, it may not impact hippocampal-dependent learning and memory in adolescence.

Infant microbiota in colic: predictive associations with problem crying and subsequent child behavior.

Infant colic is a condition of unknown cause which can result in carer distress and attachment difficulties. Recent studies have implicated the gut microbiota in infant colic, and certain probiotics have demonstrated possible efficacy. We aim to investigate whether the intestinal microbiota composition in infants with colic is associated with cry/fuss time at baseline, persistence of cry/fuss at 4-week follow-up, or child behavior at 2 years of age. Fecal samples from infants with colic (n = 118, 53% male) were analyzed using 16S rRNA sequencing. After examining the alpha and beta diversity of the clinical samples, we performed a differential abundance analysis of the 16S data to look for taxa that associate with baseline and future behavior, while adjusting for potential confounding variables. In addition, we used random forest classifiers to evaluate how well baseline gut microbiota can predict future crying time. Alpha diversity of the fecal microbiota was strongly influenced by birth mode, feed type, and child gender, but did not significantly associate with crying or behavioral outcomes. Several taxa within the microbiota (including Bifidobacterium, Clostridium, Lactobacillus, and Klebsiella) associate with colic severity, and the baseline microbiota composition can predict further crying at 4 weeks with up to 65% accuracy. The combination of machine learning findings with associative relationships demonstrates the potential prognostic utility of the infant fecal microbiota in predicting subsequent infant crying problems.

Adolescent obesity and dietary decision making-a brain-health perspective.

Adolescence represents a key period of brain development underpinned by the ongoing maturation of the prefrontal cortex-a brain region involved in the regulation of behaviour and cognition. Given the high prevalence of obesity in adolescents worldwide, this Review examines neurobiological and neurocognitive evidence describing the adolescent propensity to consume calorie-dense foods, and the neurodevelopmental mechanisms that heighten the adverse impact of these foods on brain function. The excessive consumption of calorie-dense food can undermine self-regulatory processes through effects on brain function and behavioural control. These changes could introduce enduring maladaptive eating behaviours that underlie adult obesity and related metabolic syndromes. Better understanding of links between adolescence, dietary decision making, and brain function is essential for clinicians to develop effective intervention strategies and for reducing long-term health-care costs associated with obesity.

An intermittent hypercaloric diet alters gut microbiota, prefrontal cortical gene expression and social behaviours in rats.

Objectives: Excessive consumption of high fat and high sugar (HFHS) diets alters reward processing, behaviour, and changes gut microbiota profiles. Previous studies in gnotobiotic mice also provide evidence that these gut microorganisms may influence social behaviour. To further investigate these interactions, we examined the impact of the intermittent access to a HFHS diet on social behaviour, gene expression and microbiota composition in adolescent rats. Methods: Male rats were permitted intermittent daily access (2 h / day) to a palatable HFHS chow diet for 28 days across adolescence. Social interaction, social memory and novel object recognition were assessed during this period. Following testing, RT-PCR was conducted on hippocampal and prefrontal cortex (PFC) samples. 16S ribosomal RNA amplicon sequencing was used for identification and relative quantification of bacterial taxa in faecal samples. Results: We observed reduced social interaction behaviours, impaired social memory and novel object recognition in HFHS diet rats compared to chow controls. RT-PCR revealed reduced levels of monoamine oxidase A (Maoa), catechol-O-methyltransferase (Comt) and brain derived neurotrophic factor (Bdnf) mRNA in the PFC of HFHS diet rats. Faecal microbiota analysis demonstrated that the relative abundance of a number of specific bacterial taxa differed significantly between the two diet groups, in particular, Lachnospiraceae and Ruminoccoceae bacteria. Discussion: Intermittent HFHS diet consumption evoked physiological changes to the brain, particularly expression of mRNA associated with reward and neuroplasticity, and gut microbiome. These changes may underpin the observed alterations to social behaviours.

Diet-Induced Modification of the Sperm Epigenome Programs Metabolism and Behavior.

Globally, obesity has reached epidemic proportions. The rapidly increasing numbers of overweight people can be traced back to overconsumption of energy-dense, poor-quality foods as well as physical inactivity. This development has far-reaching and costly implications. Not only is obesity associated with serious physiological and psychological complications, but mounting evidence also indicates a ripple effect through generations via epigenetic changes. Parental obesity could induce intergenerational and transgenerational changes in metabolic and brain function of the offspring. Most research has focused on maternal epigenetic and gestational effects; however, paternal contributions are likely to be substantial. We focus on the latest advances in understanding the mechanisms of epigenetic inheritance of obesity-evoked metabolic and neurobiological changes through the paternal germline that predict wide-ranging consequences for the following generation(s).

Assessing the impacts of daily Cannabis versus alcohol and methamphetamines on young Australians in youth AOD treatment.

BACKGROUND: Cannabis is the most widely used illicit substance by Australian young people, including those engaged with youth alcohol and other drug (AOD) systems. While recreational cannabis use in young people may be a developmental activity for some, for others, this usage becomes regular and be associated with poorer long term outcomes. This study reports on the rates of cannabis use and co-existing psychosocial complexity factors in the Youth Needs Census (2013 and 2016) where workers report on all clients in the youth AOD system, a cohort considered highly vulnerable. METHODS: Data was examined for two rounds of data collection for the Youth Needs Census, including 823 youth AOD service engaged young people in 2016 and 1000 AOD service engaged young people in 2013, to identify usage rates, psychosocial outcomes, and changes over time. RESULTS: Daily use of cannabis alone significantly exceeded daily usage rates for methamphetamines, alcohol, and cannabis used alongside other substances. Daily cannabis use was significantly associated with mental health problems, employment problems, education problems, family problems, and housing problems. Daily cannabis use was associated with most psychosocial complexity factors to the same extent as daily methamphetamine use and daily alcohol use, with daily cannabis users only showing lower incidence of the drug-related harm measure. Notably, daily cannabis use also increased from 2013 (47.5%) to 2016 (54.2%). CONCLUSIONS: It is imperative that the number of individuals using cannabis is considered alongside the severity of harm when assessing the social impact of this substance. Within cannabis users engaged with the youth AOD system, who often have high levels of psychosocial complexity, cannabis is used daily by a large proportion of these youths and may play a role in negatively impacting their lives.