D-Pyroglutamic acid (PCA) is a cyclic derivative of glutamic acid physiologically present in mammalian tissues. It has been shown that PCA releases GABA from the cerebral cortex and displays anti-anxiety effects in a simple approach-avoidance conflict situation in the rat.

Guvacoline hydrobromide, a pyridine alkaloid found in Areca triandra, can act as a weak full agonist of atrial and ileal mAChR.

Acetyl-(Cys4,D-Phe7,Cys10)-α-MSH (4-13)