Additionally, PFF-A (118) was a D3 and D4 receptor agonist that stimulated Gai/o-mediated-GPCR signaling, resulting in inhibition of adenylyl cyclase, as well as an antagonist to D1, serotonin 1a receptor (5HT1A), and neurokinin-1 (NK1), indicating multifactorial effects on the dopaminergic and serotonergic systems, which may be important for treating depression and/or PD [138]. Here, HTR1A is linked to major depressive disorder.