Nerve growth factor (NGF).
Brain-derived neurotrophic factor (BDNF): BDNF is a neurotrophin in the central nervous system (CNS), predominantly in the brain and the periphery. This is in contrast to NGF acting predominantly in the peripheral nervous system. It acts on certain neurons of the CNS and the peripheral nervous system that helps to support the survival of existing neurons and encourage the growth and differentiation of new neurons and synapses. In the brain, it is active in the hippocampus, cortex, and basal forebrain – areas vital to learning, memory, and higher thinking. BDNF was the second neurotrophic factor to be characterized after NGF.