Affinity and Efficacy Studies of Tetrahydrocannabinolic Acid A at Cannabinoid Receptor Types One and Two. 16 Jul Dr D Can You Pass the Acid Test? Critical Review and Novel Therapeutic Perspectives of Δ9-Tetrahydrocannabinolic Acid A. Tetrahydrocannabinolic acid is a potent PPARγ agonist with neuroprotective activity.