Isolation-linked brain circuit raises alcohol use in male mice

A mouse moves between two bottles under a miniature microscope: water on one side, a 15% alcohol solution on the other. In a preclinical study led by Northwestern University and the Salk Institute, that choice changed after some animals were moved from shared housing to isolation. Isolated male mice progressively drank more; isolated females drank less.

The researchers, including first author Reesha Patel of Northwestern's Feinberg School of Medicine, watched active brain cells while the mice freely moved and chose what to drink. The cells belonged to a pathway linking the basolateral amygdala, which processes emotional and stress signals, with the medial prefrontal cortex, which regulates decision-making.

In isolated male mice, that pathway became overactive. The team used optogenetics—brief pulses of light that switch brain circuits on or off—to test whether the activity merely accompanied drinking or helped cause it. Turning the pathway on in nonisolated male mice made their brains respond to alcohol as if they had been isolated. Turning it off in isolated males reduced alcohol consumption.

The result gives researchers a defined circuit to investigate in alcohol misuse associated with isolation, rather than only a broad link between loneliness and substance use. It also puts sex differences at the center: Patel said the study cannot yet explain why isolation pushed drinking in opposite directions in male and female mice, though some human research reports similar patterns.

And so, concretely? The immediate benefit is a laboratory target for future research, not a therapy available to people. The study was conducted in mice, and the researchers say they still need to determine how the findings translate to humans, what keeps the circuit overactive, and whether hormones or deeper circuit differences explain the contrast between sexes.