 Standard therapeutic doses of naltrexone blocks these receptors, which does two things; it prevents inhibition of GABA receptors (normally, signalling through the GABA receptors inhibits the activity of neurons; many recreational drugs inhibit GABA and thus "free up" neuronal activation; preventing inhibition of GABA allows GABA's normal inhibition activity to take place) and it blocks dopamine release (many recreational drugs stimulate dopamine release, which is part of the brain's reward system that creates pleasure).Low-dose naltrexone refers to doses about 1/10th the size of the dose used normally, typically 4.5 mg or within a couple of milligrams of that value.One hypothesis behind low-dose naltrexone's mechanism of action is that inhibiting opioid receptors at low doses might cause the body to increase production of endorphins and upregulate the immune system; it may also antagonize Toll-like receptor 4 that are found on macrophages, including microglia, and any reported anti-inflammatory effects might be due to that.