As depressive disorders affect more than 300 million people worldwide and 16.1 million officially are diagnosed in the United States, researchers continue to search for clues about the biological mechanisms that feed them.
Among the most discouraging symptoms of depression is anhedonia, which strips away the ability to enjoy experiences that once brought happiness — eating, hobbies, social engagements and sex among them.
A new study out of Spain may have better identified a particular neuronal signaling molecule that influences emotional responses to these activities, according to Medical News Today.
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Researchers at the University of Malaga — Faculty of Medicine followed up on previous animal studies that pointed to the neuropeptide galanin as a contributor to anxiety and depression-inducing mechanisms.
In the current study, published in the Journal of Psychopharmacology, the scientists looked a specific fragment of galanin to see how modifications would affect rats' desire to eat and mate.
When scientists gave the rats a concentration of the galanin fragment, they noted the rodents showed characteristic behaviors and symptoms of anhedonia. The rats had minimal interest in saccharine and mating compared to their normal levels of appreciation for these pleasures.
A closer look at the findings revealed that the brain changes in the rats impacted their dopaminergic mesolimbic system. The release of the neurotransmitter dopamine is a central part of the reward response system, which was weakened in this study by the introduction of the galanin fragment.
"We have verified through different experiments how animals modify their response to high-reinforcement appetitive stimuli, such as saccharine or sexual attraction, after the administration of the galanin fragment," co-author Carmelo Millón said.
The researchers hope the results will help them identify more precisely how galanin interacts with the brain's reward system, leading to the development of new treatments that could target both depression and addiction disorders.