oxytocin and Anhedonia

Psychological disorders such as major depressive disorder are characterised by interpersonal difficulties and anhedonia. A cognitive mechanism proposed to contribute to the maintenance of these problems is a diminished ability to generate positive mental imagery, especially regarding social interactions. The current study examined whether the effects of social imagery training on social activity and anhedonia could be enhanced with the addition of intranasal oxytocin, and whether these effects might be augmented in persons with a high propensity to engage socially (i.e., high extraversion). University students (N = 111) were randomised to self-administer intranasal oxytocin or placebo, followed by a single session of positive social or non-social imagery training that required participants to imagine 64 positive scenarios occurring in either a social or non-social context, respectively. There were no main effects of imagery type and drug, and no interaction effect on anhedonia and social activity, measured respectively via self-report and a behavioural task. Individuals low in extraversion, trust-altruism, and openness to experience reported significantly more anhedonia after receiving oxytocin relative to placebo, but only following imagery training of positive social outcomes. Results highlight the negative consequences of increasing oxytocin bioavailability after priming social contact in more withdrawn individuals.

Topics: Altruism; Anhedonia; Depressive Disorder, Major; Double-Blind Method; Extraversion, Psychological; Humans; Oxytocin; Trust

Anhedonia is a significant clinical problem in post-traumatic stress disorder (PTSD). PTSD patients show reduced motivational approach behavior, which may underlie anhedonic symptoms. Oxytocin administration is known to increase reward sensitivity and approach behavior. We therefore investigated whether oxytocin administration affected neural responses during motivational processing in PTSD patients and trauma-exposed controls.. 35 police officers with PTSD (21 males) and 37 trauma-exposed police officers without PTSD (19 males) were included in a within-subjects, randomized, placebo-controlled fMRI study. Neural responses during anticipation of monetary reward and loss were investigated with a monetary incentive delay task (MID) after placebo and oxytocin (40 IU) administration.. Oxytocin increased neural responses during reward and loss anticipation in PTSD patients and controls in the striatum, dorsal anterior cingulate cortex and insula, key regions in the reward pathway. Although PTSD patients did not differ from controls in motivational processing under placebo, anhedonia severity in PTSD patients was negatively related to reward responsiveness in the ventral striatum. Furthermore, oxytocin effects on reward processing in the ventral striatum were positively associated with anhedonia.. Oxytocin administration increased reward pathway sensitivity during reward and loss anticipation in PTSD patients and trauma-exposed controls. Thus, oxytocin administration may increase motivation for goal-directed approach behavior in PTSD patients and controls, providing evidence for a neurobiological pathway through which oxytocin could potentially increase motivation and reward sensitivity in PTSD patients.

Topics: Administration, Intranasal; Adult; Anhedonia; Anticipation, Psychological; Brain Mapping; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Motivation; Neural Pathways; Oxytocin; Police; Remuneration; Reward; Stress Disorders, Post-Traumatic; Stress, Psychological

Increasing evidence shows that higher physical activity such as running and swimming exercises is associated with decreased depression-related symptoms. However, underlying mechanisms are not fully understood. This study aimed to investigate whether oxytocinergic system can mediate the antidepressant effect of swimming exercises in mice. First, male NMRI mice were subjected to swimming training for eight weeks, then animals intraperitoneally received oxytocin antagonist (L-368899) 1 h before behavioral tests. We assessed anhedonia and social behavior and behavioral despair using the sucrose preference test, social interaction test, and tail suspension test. Oxytocin levels in the brain and serum were also measured. The results showed that swimming training decreased anhedonia and behavioral despair, whereas it increased social behavior and oxytocin levels in male mice. On the other hand, a subthreshold dose of oxytocin antagonist treatment in exercised mice prevented the antidepressant effect of swimming exercise via increased anhedonia and behavioral despair and decreased social behavior compared to the swimming training group. However, the blockade of oxytocin receptors did not affect oxytocin levels in exercised mice. Overall, these findings suggest that oxytocinergic system can play a role in mediating the antidepressant-like effect of swimming training in mice.

Topics: Anhedonia; Animals; Antidepressive Agents; Depression; Disease Models, Animal; Male; Mice; Motor Activity; Oxytocin; Swimming

Social anhedonia, a loss of interest and pleasure in social interactions, is a common symptom of major depression as well as other psychiatric disorders. Depression can occur at any age, but typically emerges in adolescence or early adulthood, which represents a sensitive period for social interaction that is vulnerable to stress. In this study, we evaluated social interaction reward using a conditioned place preference (CPP) paradigm in adolescent male and female mice. Adolescent mice of both sexes exhibited a preference for the social interaction-associated context. Chronic unpredictable stress (CUS) impaired the development of CPP for social interaction, mimicking social anhedonia in depressed adolescents. Conversely, administration of leptin, an adipocyte-derived hormone, enhanced social interaction-induced CPP in non-stressed control mice and reversed social anhedonia in CUS mice. By dissecting the motivational processes of social CPP into social approach and isolation avoidance components, we demonstrated that leptin treatment increased isolation aversion without overt social reward effect. Further mechanistic exploration revealed that leptin stimulated oxytocin gene transcription in the paraventricular nucleus of the hypothalamus, while oxytocin receptor blockade abolished the leptin-induced enhancement of socially-induced CPP. These results establish that chronic unpredictable stress can be used to study social anhedonia in adolescent mice and provide evidence that leptin modulates social motivation possibly via increasing oxytocin synthesis and oxytocin receptor activation.

Topics: Anhedonia; Animals; Depressive Disorder, Major; Female; Leptin; Male; Mice; Motivation; Oxytocin; Receptors, Oxytocin; Reward; Stress, Psychological

Although sociological studies affirm the importance of parental care in the survival of offspring, maltreatment-including child neglect-remains prevalent in many countries. While child neglect is well known to affect child development, the causes of maternal neglect are poorly understood. Here, we found that female mice with a deletion mutation of CAST (a presynaptic release-machinery protein) showed significantly reduced weaning rate when primiparous and a recovered rate when multiparous. Indeed, when nurturing, primiparous and nulliparous CAST knock out (KO) mice exhibited less crouching time than control mice and moved greater distances. Contrary to expectations, plasma oxytocin (OXT) was not significantly reduced in CAST KO mice even though terminals of magnocellular neurons in the posterior pituitary expressed CAST. We further found that compared with control mice, CAST KO mice drank significantly less water when nurturing and had a greater preference for sucrose during pregnancy. We suggest that deficiency in presynaptic release-machinery protein impairs the facilitation of some maternal behaviours, which can be compensated for by experience and learning.

Topics: Anhedonia; Animals; Cytoskeletal Proteins; Drinking; Female; Male; Maternal Behavior; Mice, Knockout; Nesting Behavior; Neurons; Oxytocin; Pituitary Gland, Posterior; Postpartum Period; Pregnancy; Smell; Sucrose; Synapses; Weaning

Chronic stressors, such as chronic isolation in social mammals, can elevate glucocorticoids, which can affect cellular mechanisms of aging, including increased levels of oxidative stress and shortened telomere lengths. Recent work in the selectively social prairie vole (Microtus ochrogaster) suggests that oxytocin and social support may mitigate some of the negative consequences of social isolation, possibly by reducing glucocorticoid levels. We investigated the influences of isolation, social support, and daily oxytocin injections in female prairie voles. Glucocorticoid levels, oxidative damage, telomere length, and anhedonia, a behavioral index of depression, were measured throughout the study. We found that six weeks of chronic isolation led to increased glucocorticoid levels, oxidative damage, telomere degradation and anhedonia. However, daily oxytocin injections in isolated voles prevented these negative consequences. These findings demonstrate that chronic social isolation in female prairie voles is a potent stressor that results in depression-like behavior and accelerated cellular aging. Importantly, oxytocin can completely prevent the negative consequences of social isolation.

Topics: Anhedonia; Animals; Arvicolinae; Cellular Senescence; Corticosterone; Depression; Female; Glucocorticoids; Oxidative Stress; Oxytocin; Social Behavior; Social Isolation; Stress, Psychological; Telomere; Telomere Shortening

Tree shrews, a species phylogenetically close to primates, are regarded as a suitable and naturalistic animal model for depression studies. However, psychological symptoms that are essential for depression diagnosis and treatment, such as helplessness and social withdrawal, have not been studied in this model. Therefore, in this study, we first investigated learned helplessness, social interaction and sucrose preference induced by two chronic stress paradigms: uncontrollable foot shocks (1-week foot shocks) and multiple unpredictable stimuli (1-week foot shocks and 3-week unpredictable stressors) in tree shrews. Our results showed that uncontrollable foot shocks could only induce learned helplessness in animals; whereas animals treated with multiple unpredictable stimuli exhibited more depression-like behaviors including social withdrawal, anhedonia and learned helplessness. These findings suggested that multiple unpredictable stimuli could effectively induce various depression-like behaviors in tree shrews. More importantly, we compared the antidepressant effects of fluoxetine and carbetocin, a long-acting oxytocin analog, on specific depression-like behaviors. Our present data displayed that, compared with fluoxetine, carbetocin was also effective in reversing learned helplessness, elevating sucrose preference and improving social interaction behaviors in depression-like animals. Therefore, carbetocin might be a potential antidepressant with applications in humans.

Topics: Anhedonia; Animals; Antidepressive Agents; Depression; Electroshock; Fluoxetine; Helplessness, Learned; Male; Oxytocin; Social Behavior; Stress, Psychological; Tupaiidae

Depression and anxiety can be severely detrimental to the health of both the affected woman and her offspring. In a rodent model of postpartum depression and anxiety, chronic social stress exposure during lactation induces deficits in maternal care and increases anxiety. Here, we extend previous findings by expanding the behavioral analyses, assessing lactation, and examining several neural systems within amygdalar and hypothalamic regions involved in the control of the stress response and expression of maternal care that may be mediating the behavioral changes in stressed dams. Compared with control dams, those exposed to chronic social stress beginning on day 2 of lactation show impaired maternal care and lactation and increased maternal anxiety on day 9 of lactation. Saccharin-based anhedonia and maternal aggression were increased and lactation was also impaired on day 16 of lactation. These behavioral changes were correlated with a decrease in oxytocin mRNA expression in the medial amygdala, and increases in the expressions of corticotrophin-releasing hormone mRNA in the central nucleus of the amygdala, glucocorticoid receptor mRNA in the paraventricular nucleus, and orexin 2 receptor mRNA in the supraoptic nucleus of stressed compared with control dams. The increase in glucocorticoid receptor mRNA in the paraventricular nucleus was negatively correlated with methylation of a CpG site in the promoter region. In conclusion, the data support the hypothesis that social stress during lactation can have profound effects on maternal care, lactation, and anxiety, and that these behavioral effects are mediated by central changes in stress and maternally relevant neuropeptide systems.

Topics: Aggression; Anhedonia; Animals; Anxiety Disorders; Brain; Chronic Disease; Depression, Postpartum; Disease Models, Animal; Female; Gene Expression; Lactation; Maternal Behavior; Orexin Receptors; Oxytocin; Rats, Sprague-Dawley; Receptors, Glucocorticoid; RNA, Messenger; Saccharin; Social Behavior; Stress, Psychological; Taste Perception