Low-dose THC boosted dopamine and GABA in the brain's reward center, while high doses decreased dopamine in mice

Low-dose THC increased dopamine and GABA in the nucleus accumbens shell, while high-dose THC decreased dopamine. The full CB1 agonist AM8936 increased all three neurotransmitters at low doses. The partial agonist AM11101 failed to substantially alter any neurotransmitter and did not produce conditioned place preference, suggesting it lacks rewarding properties.

In vivo microdialysis combined with liquid chromatography-mass spectrometry in male mice, measuring dopamine, glutamate, and GABA in the nucleus accumbens shell for 5 hours after single intraperitoneal injections of THC, AM11101, or AM8936. Conditioned place preference testing assessed rewarding effects.

Understanding how cannabinoids affect the dopamine-GABA-glutamate balance in reward circuits is fundamental to understanding both cannabis addiction potential and the development of CB1-based therapeutics that might treat pain without producing reward.

The divergent dose-response pattern (low-dose dopamine increase, high-dose decrease) helps explain why cannabis can feel rewarding at lower doses but aversive at higher ones. The finding that partial CB1 agonists avoid reward-related effects could guide development of non-addictive cannabinoid medications.

Mouse study using only male animals. Single-dose design does not capture chronic exposure effects. Synthetic agonists may not perfectly model natural cannabis use. Nucleus accumbens shell is one of several reward-related regions.