Related Experiment Video
Updated: Aug 29, 2026
Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model
Published on: September 7, 2013
Melanocortin-5 receptor deficiency promotes defensive behavior in male mice
Caurnel Morgan1, Ruth E Thomas, Roger D Cone
1Vollum Institute for Advanced Biomedical Research, Oregon Health and Science University, Portland, OR 97239, USA. cam2025@med.cornell.edu
Abstract:
The endogenous melanocortin, alpha-melanocyte-stimulating hormone (alpha-MSH), is a neurohormone secreted by the neurointermediate lobe of the pituitary. Alpha-MSH promotes intermale aggression in mice by influencing pheromone secretion, but the role of specific melanocortin receptors has not been determined. We assessed mice made deficient in the gene for the melanocortin-5 receptor (MC5R) to determine its role in pheromone-regulated behavior. In heterotypic pairs assessed in the social interaction test (SIT), MC5R-deficient mice exhibited less aggressive behavior and more defensive behavior than their wild-type opponents. By contrast, when assessed in homotypic pairs and against stimulus animals in the SIT, MC5R-deficient and wild-type mice behaved similarly. Moreover, urine from MC5R deficient mice stimulated more aggression than did urine from wild-type mice. The results suggest that MC5R deficiency disinhibits an aggression-suppressing pheromonal signal.
Insights
Melanocortin-5 receptor (MC5R) deficiency in mice alters aggression and defensive behaviors. MC5R-deficient mice exhibit reduced aggression, suggesting MC5R influences pheromone-regulated social interactions.
Area of Science:
- Neuroendocrinology
- Behavioral Neuroscience
- Genetics
Background:
- Alpha-melanocyte-stimulating hormone (alpha-MSH) is an endogenous neurohormone.
- Alpha-MSH influences intermale aggression in mice via pheromone secretion.
- The specific melanocortin receptors involved remain largely undetermined.
Purpose of the Study:
- To investigate the role of the melanocortin-5 receptor (MC5R) in pheromone-regulated behavior.
- To assess the impact of MC5R deficiency on social interaction and aggression in mice.
Main Methods:
- Utilized gene-deficient mice lacking the melanocortin-5 receptor (MC5R).
- Employed the social interaction test (SIT) with heterotypic and homotypic pairings.
- Analyzed behavioral responses including aggression and defensive actions.
- Assessed the effect of urine from MC5R-deficient and wild-type mice on aggression.
Main Results:
- MC5R-deficient mice displayed reduced aggression and increased defensive behavior in heterotypic pairings.
- No significant behavioral differences were observed between MC5R-deficient and wild-type mice in homotypic pairings or against stimulus animals.
- Urine from MC5R-deficient mice elicited greater aggression compared to urine from wild-type mice.
Conclusions:
- Melanocortin-5 receptor (MC5R) plays a role in modulating aggression in male mice.
- MC5R deficiency appears to disinhibit an aggression-suppressing pheromonal signal.
- These findings highlight the involvement of MC5R in the neurobiology of social behavior and pheromonal communication.
