Psychoneuroendocrinology
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Psychoneuroendocrinology · Apr 2014
17β Estradiol increases resilience and improves hippocampal synaptic function in helpless ovariectomized rats.
Memory impairment is the most commonly reported cognitive symptom associated with major depressive disorder. Decreased hippocampal volume and neurogenesis in depression link hippocampal dysfunction with deficits in memory. Stress decreases hippocampal dendritic spine density and long-term potentiation (LTP) at glutamate synapses, a cellular correlate of learning and memory. ⋯ In contrast, significant LTP was observed in slices from E2-treated helpless rats; importantly, spine density was not different between E2-treated helpless and resilient rats, dissociating spine density from the LTP magnitude. We also find that E2 replacement can reverse previously established helpless behavior. Thus, our results show that E2 replacement in OVX rats increases resilience and improves hippocampal plasticity, suggesting that E2 therapy may increase resilience to stress and preserve hippocampal function in women experiencing large fluctuations in plasma estrogen levels.
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The stress hormone cortisol reduces retrieval of emotional memories, which has been suggested to support the treatment of psychiatric disorders characterized by exaggerated fear-related memories. Indeed, studies in patients with anxiety disorders have indicated that the success of exposure therapy can be enhanced with accompanying cortisol administration. Fear renewal refers to the clinically relevant phenomenon that successfully extinguished fear can return after a context change. ⋯ These results demonstrate a decreased return of fear after acute exposure to stress. Stress interferes with the retrieval of the original fear memory which in turn affects extinction responding. Thus, acute stress reduces rather than promotes the return of fear.
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Psychoneuroendocrinology · Jan 2014
Randomized Controlled TrialAcute stress-induced cortisol elevations mediate reward system activity during subconscious processing of sexual stimuli.
Stress is thought to alter motivational processes by increasing dopamine (DA) secretion in the brain's "reward system", and its key region, the nucleus accumbens (NAcc). However, stress studies using functional magnetic resonance imaging (fMRI), mainly found evidence for stress-induced decreases in NAcc responsiveness toward reward cues. Results from both animal and human PET studies indicate that the stress hormone cortisol may be crucial in the interaction between stress and dopaminergic actions. ⋯ Although generally stress decreases activation in the NAcc in response to rewarding stimuli, high stress-induced cortisol levels suppress this relation, and are associated with stronger NAcc activation. Individuals with a high cortisol response to stress might on one hand be protected against reductions in reward sensitivity, which has been linked to anhedonia and depression, but they may ultimately be more vulnerable to increased reward sensitivity, and addictions. Future studies investigating effects of stress on reward sensitivity should take into account the severity of the stressor and the individual cortisol response to stress.
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Psychoneuroendocrinology · Jan 2014
Randomized Controlled TrialSex differences in the neural and behavioral response to intranasal oxytocin and vasopressin during human social interaction.
Both oxytocin (OT) and vasopressin (AVP) are known to modulate social behavior, and dysfunction in both systems has been postulated as a potential cause of certain psychiatric disorders that involve social behavioral deficits. In particular, there is growing interest in intranasal OT as a potential treatment for certain psychiatric disorders, and preliminary pre-clinical and clinical studies suggest efficacy in alleviating some of the associated symptoms. However, the vast majority of research participants in these studies have been male, and there is evidence for sexually differentiated effects of nonapeptides in both humans and non-human animals. ⋯ During cooperative interactions, both OT and AVP increased brain activity in men within areas rich in OT and AVP receptors and in areas playing a key role in reward, social bonding, arousal and memory (e.g., the striatum, basal forebrain, insula, amygdala and hippocampus), whereas OT and AVP either had no effect or in some cases actually decreased brain activity in these regions in women. OT treatment rendered neural responses of males more similar to responses of females in the placebo group and vice versa, raising the prospect of an inverted u-shaped dose response to central OT levels. These findings emphasize the need to fully characterize the effects of intranasal OT and AVP in both males and females and at multiple doses before widespread clinical application will be warranted.
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Psychoneuroendocrinology · Dec 2013
Randomized Controlled TrialGiving peace a chance: oxytocin increases empathy to pain in the context of the Israeli-Palestinian conflict.
Studies have argued that empathy to the pain of out-group members is largely diminished by "in-group empathy bias". Investigating the mechanism underlying the emotional reactions of Jewish Israeli participants toward the pain experienced by Palestinians in the context of the Israeli-Palestinian conflict affords a natural experiment that allows us to examine the role of neurohormones in emotion sensitivity across conflicting social groups. ⋯ Oxytocin remarkably increased empathy to the pain of Palestinians, attenuating the effect of in-group empathy bias observed under the placebo condition. This effect, we argue, is driven by the general role of oxytocin in increasing the salience of social agents which, in turn, may interfere with processes pertaining to derogation of out-group members during intractable conflicts.