Collateralizing ventral subiculum melanocortin 4 receptor circuits regulate energy balance and food motivation.

Hippocampal dysfunction is associated with major depressive disorder, a serious mental illness characterized by not only depressed mood but also appetite disturbance and dysregulated body weight. However, the underlying mechanisms by which hippocampal circuits regulate metabolic homeostasis remain incompletely understood. Here we show that collateralizing melanocortin 4 receptor (MC4R) circuits in the ventral subiculum (vSUB), one of the major output structures of the hippocampal formation, affect food motivation and energy balance. Viral-mediated cell type- and projection-specific input-output circuit mapping revealed that the nucleus accumbens shell (NAcSh)-projecting vSUBMC4R+ neurons send extensive collateral projections of to various hypothalamic nuclei known to be important for energy balance, including the arcuate, ventromedial and dorsomedial nuclei, and receive monosynaptic inputs mainly from the ventral CA1 and the anterior paraventricular nucleus of thalamus. Chemogenetic activation of NAcSh-projecting vSUBMC4R+neurons lead to increase in motivation to obtain palatable food without noticeable effect on homeostatic feeding. Viral-mediated restoration of MC4R signaling in the vSUB partially restores obesity in MC4R-null mice without affecting anxiety- and depression-like behaviors. Collectively, these results delineate vSUBMC4R+ circuits to the unprecedented level of precision and identify the vSUBMC4R signaling as a novel regulator of food reward and energy balance.

A novel task of canine olfaction for use in adult and senior pet dogs.

While much work has been done in the field of canine olfaction, there has been little exploration of hyposmia or anosmia. This is partly due to difficulties in reducing confounds like training history and environmental distraction. The current study describes a novel olfaction test using spontaneous search behavior in dogs to find a hidden food treat in a three-choice task with both light-phase and dark-phase conditions. The study was performed in 18 adult control dogs, 18 senior/geriatric dogs enrolled in a longitudinal aging study, and a single dog with severe nasal pathology. In the senior/geriatric and control groups, dogs performed with higher accuracy (p < 0.0001) and were less likely to show biased selection strategy (p < 0.01) in the dark-phase than light-phase. While senior/geriatric dogs performed above chance, they had lower accuracy in the dark-phase compared to controls (p = 0.036). Dogs who scored higher on an owner questionnaire of cognitive decline showed a positive correlation with performance in the dark-phase; performance on additional cognitive tests did not correlate with performance in the dark-phase. This task can be used to quantify canine olfaction using clearly defined endpoints and spontaneous behaviors thus making it feasible to compare between and within groups of pet dogs.

Relationship between hearing, cognitive function, and quality of life in aging companion dogs.

BACKGROUND: Elderly people with presbycusis are at higher risk for dementia and depression than the general population. There is no information regarding consequences of presbycusis in dogs. OBJECTIVE: Evaluate the relationship between cognitive function, quality of life, and hearing loss in aging companion dogs. ANIMALS: Thirty-nine elderly companion dogs. METHODS: Prospective study. Hearing was evaluated using brainstem auditory evoked response (BAER) testing. Dogs were grouped by hearing ability. Owners completed the canine dementia scale (CADES) and canine owner-reported quality of life (CORQ) questionnaire. Cognitive testing was performed, and cognitive testing outcomes, CADES and CORQ scores and age were compared between hearing groups. RESULTS: Nineteen dogs could hear at 50 dB, 12 at 70 dB, and 8 at 90 dB with mean ages (months) of 141 ± 14, 160 ± 16, and 172 ± 15 for each group respectively (P = .0002). Vitality and companionship CORQ scores were significantly lower as hearing deteriorated (6.6-5.4, 50-90 dB group, P = .03 and 6.9-6.2, 50-90 dB group, P = .02, respectively). Cognitive classification by CADES was abnormal in all 90 dB group dogs and normal in 3/12 70 dB group and 11/19 50 dB group dogs (P = .0004). Performance on inhibitory control, detour and sustained gaze tasks decreased significantly with hearing loss (P = .001, P = .008, P = .002, respectively). In multivariate analysis, higher CADES score was associated with worse hearing (P = .01). CONCLUSIONS AND CLINICAL IMPORTANCE: Presbycusis negatively alters owner-pet interactions and is associated with poor executive performance and owner-assessed dementia severity.

Use of Cognitive Testing, Questionnaires, and Plasma Biomarkers to Quantify Cognitive Impairment in an Aging Pet Dog Population.

BACKGROUND: Aging dogs may suffer from canine cognitive dysfunction syndrome (CCDS), a condition in which cognitive decline is associated with amyloid pathology and cortical atrophy. Presumptive diagnosis is made through physical examination, exclusion of systemic/metabolic conditions, and completion of screening questionnaires by owners. OBJECTIVE: This study aimed to determine whether cognitive function could be quantified in aging pet dogs, and to correlate cognitive testing with validated questionnaires and plasma neurofilament light chain (pNfL) concentration. METHODS: Thirty-nine dogs from fifteen breeds were recruited (9.3 to 15.3 years). Owners completed the Canine Dementia Scale (CADES) and Canine Cognitive Dysfunction Rating scale (CCDR). Executive control and social cues were tested, and pNfL was measured with single molecule array assay. Comparisons were made between cognitive testing scores, CADES, CCDR scores, and pNfL. RESULTS: CADES scoring classified five dogs as severe CCDS, six as moderate, ten as mild, and eighteen as normal. CCDR identified seven dogs at risk of CCDS and thirty-two as normal. Cognitive testing was possible in the majority of dogs, although severely affected dogs were unable to learn tasks. CADES score correlated with sustained attention duration (r = -0.47, p = 0.002), inhibitory control (r = -0.51, p = 0.002), detour (r = -0.43, p = 0.001), and pNfL (r = 0.41, p = 0.025). Concentration of pNfL correlated with inhibitory control (r = -0.7, p≤0.001). The CCDR scale correlated with performance on inhibitory control (r = -0.46, p = 0.005). CONCLUSION: Our findings suggest that a multi-dimensional approach using a combination of questionnaires, specific cognitive tests, and pNfL concentration can be used to quantify cognitive decline in aging pet dogs.

Relationship between engagement with the impossible task, cognitive testing, and cognitive questionnaires in a population of aging dogs.

Introduction: The aim of this study was to evaluate the engagement of aging dogs with a cognitively challenging and potentially frustrating task (the impossible task). Based on previous observations, we predicted that dogs showing signs of cognitive impairment in other cognitive tests and owner-completed questionnaires would show reduced engagement with the task. Methods: In this task, dogs were shown a piece of food in a clear container that they could not open; time spent interacting with the container and the experimenter was measured. While the impossible task has not been used as a measure of frustration, the parameters of the test design creates a potential frustrate state, making this assessment appropriate. Thirty-two dogs enrolled in a longitudinal aging study participated in the study. Owners were asked to complete two cognitive dysfunction screening questionnaires (Canine Dementia Scale [CADES] and Canine Cognitive Dysfunction Rating Scale [CCDR]) as well a questionnaire assessing general frustration. Dogs participated in multiple measures of cognitive function as well the impossible task. Results: Latency to disengage from the impossible task was faster for dogs with higher total (more impaired) CADES (p = 0.02) and total CCDR (p = 0.04) scores. Latency to disengage also correlated with decreased performance in cognitive tests observing social cues (p = 0.01), working memory (p ≤ 0.001), spatial reasoning and reversal learning (p = 0.02), and sustained attention (p = 0.02). Discussion: The high correlation with several cognitive measures and the ease of administration of this test makes it a useful tool in evaluating canine cognitive dysfunction syndrome, however it is unclear if increased frustration or other cognitive processes are contributing to the observed changes.

(-)-P7C3-S243 Protects a Rat Model of Alzheimer's Disease From Neuropsychiatric Deficits and Neurodegeneration Without Altering Amyloid Deposition or Reactive Glia.

BACKGROUND: In addition to cognitive deficits, Alzheimer's disease (AD) is associated with other neuropsychiatric symptoms, including severe depression. Indeed, depression often precedes cognitive deficits in patients with AD. Unfortunately, the field has seen only minimal therapeutic advances, underscoring the critical need for new treatments. P7C3 aminopropyl carbazoles promote neuronal survival by enhancing nicotinamide adenine dinucleotide flux in injured neurons. Neuroprotection with P7C3 compounds has been demonstrated in preclinical models of neurodegeneration by virtue of promoting neuronal survival independently of early disease-specific pathology, resulting in protection from cognitive deficits and depressive-like behavior. We hypothesize that P7C3 compounds might be uniquely applicable to patients with AD, given the comorbid presentation of depression and cognitive deficits. METHODS: Aging male and female wild-type and TgF344-AD rats, a well-characterized preclinical AD model, were administered (-)-P7C3-S243 daily for 9 and 18 months, beginning at 6 months of age. Behavioral phenotypes related to cognition and depression were assessed at 15 and 24 months, and brain pathology and biochemistry were assessed at 24 months. RESULTS: (-)-P7C3-S243 safely protected aging male and female wild-type and TgF344-AD rats from cognitive deficits and depressive-like behavior. Depressive-like behavior occurred earlier than cognitive deficits in TgF344-AD rats, consistent with AD in many patients. Treatment with (-)-P7C3-S243 blocked neurodegeneration in TgF344-AD rats, without altering amyloid deposition or indicators of neuroinflammation. CONCLUSIONS: Neuronal cell death-specific treatment approaches, such as P7C3 compounds, may represent a new treatment approach for patients experiencing the combination of cognitive deficits and depression associated with AD.

The Eating-Disorder Associated HDAC4A778T Mutation Alters Feeding Behaviors in Female Mice.

BACKGROUND: While eating disorders (EDs) are thought to result from a combination of environmental and psychological stressors superimposed on genetic vulnerability, the neurobiological basis of EDs remains incompletely understood. We recently reported that a rare missense mutation in the gene for the transcriptional repressor histone deacetylase 4 (HDAC4) is associated with the risk of developing an ED in humans. METHODS: To understand the biological consequences of this missense mutation, we created transgenic mice carrying this mutation by introducing the alanine to threonine mutation at position 778 of mouse Hdac4 (corresponding to position 786 of the human protein). Bioinformatic analysis to identify Hdac4-regulated genes was performed using available databases. RESULTS: Male mice heterozygous for HDAC4A778T did not show any metabolic or behavioral differences. In contrast, female mice heterozygous for HDAC4A778T display several ED-related feeding and behavioral deficits depending on housing condition. Individually housed HDAC4A778T female mice exhibit reduced effortful responding for high-fat diet and compulsive grooming, whereas group-housed female mice display increased weight gain on high-fat diet, reduced behavioral despair, and increased anxiety-like behaviors. Bioinformatic analysis identifies mitochondrial biogenesis including synthesis of glutamate/gamma-aminobutyric acid as a potential transcriptional target of HDAC4A778T activity relevant to the behavioral deficits identified in this new mouse model of disordered eating. CONCLUSIONS: The HDAC4A778T mouse line is a novel model of ED-related behaviors and identifies mitochondrial biogenesis as a potential molecular pathway contributing to behavioral deficits.

Loss of estrogen-related receptor alpha disrupts ventral-striatal synaptic function in female mice.

Eating disorders (EDs), including anorexia nervosa, bulimia nervosa and binge-ED, are mental illnesses characterized by high morbidity and mortality. While several studies have identified neural deficits in patients with EDs, the cellular and molecular basis of the underlying dysfunction has remained poorly understood. We previously identified a rare missense mutation in the transcription factor estrogen-related receptor alpha (ESRRA) associated with development of EDs. Because ventral-striatal signaling is related to the reward and motivation circuitry thought to underlie EDs, we performed functional and structural analysis of ventral-striatal synapses in Esrra-null mice. Esrra-null female, but not male, mice exhibit altered miniature excitatory postsynaptic currents on medium spiny neurons (MSNs) in the ventral striatum, including increased frequency, increased amplitude, and decreased paired pulse ratio. These electrophysiological measures are associated with structural and molecular changes in synapses of MSNs in the ventral striatum, including fewer pre-synaptic glutamatergic vesicles and enhanced GluR1 function. Neuronal Esrra is thus required for maintaining normal synaptic function in the ventral striatum, which may offer mechanistic insights into the behavioral deficits observed in Esrra-null mice.

Behavioral disturbances in estrogen-related receptor alpha-null mice.

Eating disorders, such as anorexia nervosa and bulimia nervosa, are common and severe mental illnesses of unknown etiology. Recently, we identified a rare missense mutation in the transcription factor estrogen-related receptor alpha (ESRRA) that is associated with the development of eating disorders. However, little is known about ESRRA function in the brain. Here, we report that Esrra is expressed in the mouse brain and demonstrate that Esrra levels are regulated by energy reserves. Esrra-null female mice display a reduced operant response to a high-fat diet, compulsivity/behavioral rigidity, and social deficits. Selective Esrra knockdown in the prefrontal and orbitofrontal cortices of adult female mice recapitulates reduced operant response and increased compulsivity, respectively. These results indicate that Esrra deficiency in the mouse brain impairs behavioral responses in multiple functional domains.

P7C3 neuroprotective chemicals block axonal degeneration and preserve function after traumatic brain injury.

The P7C3 class of neuroprotective aminopropyl carbazoles has been shown to block neuronal cell death in models of neurodegeneration. We now show that P7C3 molecules additionally preserve axonal integrity after injury, before neuronal cell death occurs, in a rodent model of blast-mediated traumatic brain injury (TBI). This protective quality may be linked to the ability of P7C3 molecules to activate nicotinamide phosphoribosyltransferase, the rate-limiting enzyme in nicotinamide adenine dinucleotide salvage. Initiation of daily treatment with our recently reported lead agent, P7C3-S243, 1 day after blast-mediated TBI blocks axonal degeneration and preserves normal synaptic activity, learning and memory, and motor coordination in mice. We additionally report persistent neurologic deficits and acquisition of an anxiety-like phenotype in untreated animals 8 months after blast exposure. Optimized variants of P7C3 thus offer hope for identifying neuroprotective agents for conditions involving axonal damage, neuronal cell death, or both, such as occurs in TBI.