CB1 receptor
What it is
Primary psychoactive target of THC. Heavily expressed in cortex, hippocampus, basal ganglia, hypothalamus, and mesolimbic reward circuitry.
Why it matters
CB1 activation explains:
- acute HR rise and autonomic shift
- appetite stimulation (hypothalamic CB1)
- sleep architecture disruption
- tolerance, withdrawal, and detection difficulty in chronic users
Key evidence
- Chronic heavy use → 15–20% CB1 availability reduction (PET imaging; cortical regions most affected)
- CB1 normalization begins ~2 days abstinence; near-complete by ~4 weeks
- Withdrawal severity inversely correlates with CB1 availability during early abstinence
Tolerance implication for Vitals
CB1 downregulation in heavy users = weaker acute HR spike = harder biometric detection even at doses that still cause sleep/cognitive harm.