Four widely abused drugs—heroin, nicotine, cocaine, and MDMA—modulate the activity of midbrain dopamine and serotonin neurons in mice with distinct potency and timing. Heroin strongly activates dopamine neurons but excites serotonin neurons only at higher doses. Nicotine activates dopamine neurons within seconds and has minimal effect on serotonin neurons. Cocaine and MDMA cause long-lasting suppression of both neuron types, with MDMA more profoundly inhibiting serotonin neurons. These inhibitory effects depend on dopamine and serotonin autoreceptors. The findings suggest that dopamine neuron activity relates more to a drug's reinforcing property, while serotonin neuron activity relates more to its euphorigenic property.
A single intravenous injection of esketamine (0.5 mg/kg) given during general anesthesia induction reduced postoperative anxiety and depression in female thyroid cancer patients. In a randomized, double-blind, placebo-controlled trial, 80 women received either esketamine or saline. Those given esketamine had significantly lower anxiety and depression scores on the second day after surgery, along with higher levels of mature brain-derived neurotrophic factor and serotonin, and lower insulin-like growth factor-1. They also required fewer vasopressors during surgery, suggesting more stable hemodynamics. The findings indicate that esketamine may help prevent postoperative mood disturbances, possibly through changes in these serum factors.