Melanotan II · research summary

Melanocortin agonism in a social context selectively activates nucleus accumbens in an oxytocin-dependent manner.

Neuropharmacology · 2024. Summary drawn from the study's full text. Each statement is followed by the exact sentence it comes from. This is a research summary, not medical advice.

Study type

Preclinical animal study investigating neuronal activation via Fos expression in prairie voles
“To model pharmacological activation of the endogenous oxytocin system during behavioral therapy, we administered MTII prior to social interactions between male and female voles.”

Subjects

Adult, sexually-naïve male and female prairie voles (Microtus ochrogaster), including wildtype and Oxtr-knockout genotypes
“All experiments used adult (75–186 days of age), sexually-naïve male (M) and female (F) prairie voles (Microtus ochrogaster) from our outbred colony at Emory University.”

Sample size

Variable group sizes ranging from 10 to 20 subjects per experimental condition across multiple experiments
“On the day of the experiment, voles received intraperitoneal (i.p.) injections of either 0.3 mL 0.9% saline (Pfizer, New York, NY) or 10 mg/kg MTII (Toronto Research Chemicals, Toronto, ON) dissolved in 0.9% saline and were then returned, alone, to their home cages.”

Duration

Acute administration with behavioral observation periods of 30 to 60 minutes followed by tissue analysis
“Forty-five minutes after injection, a novel, opposite-sex stimulus animal (intact males, ovariectomized females) was placed in the test cage.”

Reported findings

MTII increased Fos expression in the hypothalamic paraventricular nucleus in both social and non-social contexts
“In non-social contexts, MTII only activated hypothalamic paraventricular nucleus, a primary site of oxytocin synthesis.”
MTII selectively increased oxytocin-dependent activation of the nucleus accumbens only during social interactions
“However, during social interactions, MTII selectively increased oxytocin-dependent activation of nucleus accumbens, a site critical for social learning.”
The increase in nucleus accumbens activation was dependent on oxytocin signaling and not driven by changes in social behavior
“The similarity of the MTII treatment effects on behavior in both genotypes suggests that behavioral differences did not drive the MTII-induced increase in NAc Fos that occurred only in WT animals.”

Source: PubMed 38253222 · DOI 10.1016/j.neuropharm.2024.109848 · all study summaries

Subjects

Adult, sexually-naïve male and female prairie voles (Microtus ochrogaster), including wildtype and Oxtr-knockout genotypes

“All experiments used adult (75–186 days of age), sexually-naïve male (M) and female (F) prairie voles (Microtus ochrogaster) from our outbred colony at Emory University.”

Sample size

Variable group sizes ranging from 10 to 20 subjects per experimental condition across multiple experiments

“On the day of the experiment, voles received intraperitoneal (i.p.) injections of either 0.3 mL 0.9% saline (Pfizer, New York, NY) or 10 mg/kg MTII (Toronto Research Chemicals, Toronto, ON) dissolved in 0.9% saline and were then returned, alone, to their home cages.”

Reported findings

MTII increased Fos expression in the hypothalamic paraventricular nucleus in both social and non-social contexts

“In non-social contexts, MTII only activated hypothalamic paraventricular nucleus, a primary site of oxytocin synthesis.”

MTII selectively increased oxytocin-dependent activation of the nucleus accumbens only during social interactions

“However, during social interactions, MTII selectively increased oxytocin-dependent activation of nucleus accumbens, a site critical for social learning.”

The increase in nucleus accumbens activation was dependent on oxytocin signaling and not driven by changes in social behavior

“The similarity of the MTII treatment effects on behavior in both genotypes suggests that behavioral differences did not drive the MTII-induced increase in NAc Fos that occurred only in WT animals.”