Chronic stress can lead to significant mental health conditions, including depression, Post Traumatic Stress Disorder (PTSD), and loss of pleasure. Scientists discovered that recurring stress increases the hyperactivity of proopiomelanocortin (POMC) neurons found in the hypothalamus’s arcuate nucleus (ARC), a bow-shaped brain structure involved in regulating responses to chronic stress. Examining activity in the hypothalamus reveals insights into functions such as releasing hormones and regulating hunger, thirst, mood, sex drive, and sleep. When POMC neurons become very active, behavioral problems result. By reducing POMC neural activity, the researchers found it minimized the behaviors. The findings have been published in the journal Molecular Psychiatry.
The researchers studied how POMC neurons responded to 10 days of chronic, unpredictable stress. Chronic unpredictable stress is often used to study the impact of stress exposure in animal models. Behaviors like restraint, prolonged wet bedding in a tilted cage, and social isolation might be negative signs of their responses to stress. The researchers found that stressors increased the spontaneous firing of these POMC neurons in mice.
Rather than letting stress increase neuronal firing, the researchers directly activated the neurons and found this action intensified depression and the inability to feel pleasure (a condition called anhedonia). Human behavior indicators of anhedonia include decreased socializing and decreased sex drive. Mice have less interest in sugar water (usually an enticing treat), and male mice also demonstrate a decreased sex drive. The researchers also found that when they inhibited the neurons’ firing, it reduced stress-induced behavioral changes.
The study indicated POMC neurons play a key role in increasing chronic stress susceptibility. Previous research has established that POMC neurons play a critical role in food intake, body weight, and glucose homeostasis. This study has contributed to the scholarship on POMC neuron activity leading to mood disorders like depression.
Sources: Eureka News Alert, Molecular Psychiatry