GAT228 is an allosteric agonist of cannabinoid receptor 1 (CB), the R-(+)-enantiomer of the CB positive allosteric modulator (PAM) GAT229 , and a component of the racemic mixture GAT211, which acts as both an agonist and PAM. GAT228 increases β-arrestin recruitment, cAMP inhibition, and ERK1/2 and PLCβ3 phosphorylation in HEK293A cells expressing GFP-tagged human CB (hCB-GFP) in a concentration-dependent manner. Unlike GAT229, GAT228 has no effect on the binding of the CB receptor agonist CP 55,940 to membranes from CHO cells expressing hCB when used at concentrations up to 1 µM. It inhibits excitatory postsynaptic currents (EPSCs) in a subset of CB-expressing murine autaptic hippocampal neurons when used at a concentration of 1 µM.