The neuroprotective effects of cholecystokinin in the brain: antioxidant, anti-inflammatory, cognition, and synaptic plasticity

Cholecystokinin (CCK) is a major neuropeptide in the brain that functions as a neurotransmitter, hormone, and growth factor. The peptide and its receptors are widely expressed in the brain. CCK signaling modulates synaptic plasticity and can improve or impair memory formation, depending on the brain areas studies and the receptor subtype activated. Studies have shown in a series of animal models of neurodegenerative diseases that CCK receptor agonists show neuroprotective effects and can effectively alleviate oxidative stress, alleviate chronic inflammation of the central nervous system, improve neuronal synaptic plasticity, prevent neuronal loss, and improve cognitive dysfunction in Alzheimer's disease (AD) model mice and motor activity in animal models of Parkinson's disease. In addition, CCK plays important roles in the amygdala to regulate anxiety and depressive states. Activation of interneurons or inhibition of excitatory neurons can improve anxiety levels. This review summarizes the effects on memory formation and synaptic plasticity, the neuroprotective effects of cholecystokinin and its analogs in neurological diseases such as Alzheimer and Parkinson's disease, and the effects on anxiety and neuronal activity in the amygdala.