Melanocortin receptor agonist melanotan-II microinjected in the nucleus accumbens decreases appetitive and consumptive responding for food.

Preclinical animal study investigating the effects of melanocortin receptor agonists on feeding behaviors and metabolism.

“These studies sought to determine the role of melanocortins in the NAcc on consumption of and motivation to obtain access to standard rodent chow.”

Adult male C57BL/6J mice.

“Adult, male, C57BL6/J mice (The Jackson Laboratory) were used for all studies and arrived at 2–3 months of age.”

Sample sizes varied by experimental condition, ranging from 5 to 12 mice per group.

“mice (n=12) were moved to a clean cage with no access to food.”

Experiments involved acute microinjections with behavioral and metabolic measurements taken over periods ranging from 1 hour to 24 hours post-injection.

“The food was weighed again at 1, 2, 4, 6, and 24 hours after injection to determine how much food was consumed.”

Microinjection of MT-II into the NAcc significantly decreased food consumption in both home cage and operant paradigms.

“MT-II injected into the NAcc significantly decreased consumption in both home cage and operant paradigms, and furthermore decreased appetitive responding to gain access to food.”

MT-II administration did not produce conditioned taste avoidance or alter metabolic parameters.

“There was no development of conditioned taste avoidance or change in metabolic parameters following anorexic doses of MT-II.”

MT-II decreased the motivation to eat (appetitive responding) independent of food intake.

“MT-II in the NAcc decreased both the motivation to eat and the amount of food consumed without inducing an aversive state or affecting metabolic rate.”

Mice were singly housed after surgery, which is a known stressor in rodents that may influence the melanocortinergic system.

“Mice in these studies were singly housed as group housing of mice with head mount cannualae was not a viable option, and this is a known stressor in rodents.”