NMDA Glutamate Receptor

Amygdala

The threat detector. Dense in androgen receptors, and the structure most implicated in the anger, vigilance and fear side of what these compounds do. Splitting it out of the limbic system matters because threat processing and reward processing sit in the same blob otherwise, and compounds pull them in opposite directions.

Hippocampus

Where new memory is laid down. Unusually sensitive to sustained cortisol and to lost deep sleep, both of which these compounds can produce, which makes it the structure behind most reported memory complaints.

Prefrontal Cortex

Planning, judgement and the brake on impulse. Relevant here because the reported behaviour change on these compounds is often better described as a weaker brake than as a stronger drive, and those two have different consequences.

Excitotoxic Injury

Death by over-stimulation. Glutamate opens calcium channels, calcium floods in past what the mitochondria can hold, and the cell triggers its own destruction. It is the final common path for a large share of neuronal death, and it is the exact process estrogen defends against.

Dendritic Spine Density

How many connection points a neuron carries. Spines appear and disappear over hours, and their number is the physical substrate of how much a circuit can currently hold. Estradiol raises spine density in hippocampal CA1, and the effect tracks the hormone.

Synaptic Plasticity

The brain's ability to strengthen and rebuild connections. It is what learning physically is, and it is the endpoint almost every nootropic peptide claims.