(5R,6R)6-(3-propylthio-1,2,5-thiadiazol-4-yl)-1-azabicyclo[3.2.1]octane

PTAC, chemically known as (5R,6R)6-(3-propylthio-1,2,5-thiadiazol-4-yl)-1-azabicyclo[3.2.1]octane, is a potent small molecule ligand targeting muscarinic receptors. It exhibits high affinity for central muscarinic receptors with significantly lower affinity for other receptor types, including dopamine receptors. PTAC acts as a partial agonist at muscarinic M2 and M4 receptors, while demonstrating antagonist effects at muscarinic M1, M3, and M5 receptors. This unique pharmacological profile leads to functional dopamine receptor antagonism, despite PTAC not directly binding to dopamine receptors. Preclinical studies have shown that PTAC can inhibit conditioned avoidance responding and dopamine receptor agonist-induced behaviors without causing typical antipsychotic side effects like catalepsy, tremor, or salivation at relevant doses. It also selectively inhibits dopamine cell firing in the limbic ventral tegmental area. These findings suggest PTAC and similar muscarinic receptor partial agonists could represent a novel therapeutic approach for conditions like schizophrenia.