Microglial Phagocytosis of Newborn Cells Is Induced by Endocannabinoids and Sculpts Sex Differences in Juvenile Rat Social Play.
Level 5 - mechanism / opinion, no new human data
Mechanistic laboratory research in an animal model (rats) without human data.
PubMed 30827729 · doi:10.1016/j.neuron.2019.02.006
What was done
Investigated the cellular and molecular mechanisms driving sex differences in juvenile rough-and-tumble play behavior in rats using experimental manipulations of androgen signaling, endocannabinoid tone, microglial phagocytic activity, and complement pathways during a perinatal critical period of amygdala development.
What was found
The abstract reports no numerical values or sample sizes. Directionally, androgen-induced increases in endocannabinoid tone enhanced microglial phagocytosis of viable newborn cells in the developing male amygdala compared to females, leading to lower astrocyte survival in males. Blocking complement-dependent phagocytosis in males increased astrocyte survival and prevented the masculinization of juvenile social play, while higher astrocyte density in the juvenile amygdala reduced neuronal excitation during play.
Why it matters
This paper identifies a non-neuronal mechanism of mammalian brain sexual differentiation, showing that endocannabinoid-induced microglial phagocytosis of developing astrocytes sculpts sex-specific social play circuits.
Limits
Conducted entirely in rats with unknown generalizability to humans. The abstract omits sample sizes, exact effect sizes, quantitative metrics, variance measures, and specifics regarding how phagocytosis was blocked or excitation was measured.