The author has studied nerve growth factor (NGF) and its family of neurotrophic factors (neurotrophins) for over 40 years. During the first 20 years, my laboratory established a highly sensitive enzyme immunoassay for NGF and analyzed the regulatory mechanism of NGF synthesis in cultured primary cells. Fibroblast cells cultured from peripheral organs such as the heart and astrocytes from the brain produced a substantial amount of NGF in a growth-dependent manner. Furthermore, synthesis of NGF in these cells could be upregulated by catechol compounds including catecholamines. This observation might explain a physiological relation between the level of NGF mRNA and the density of innervation in the peripheral sympathetic nervous systems. Over the subsequent 20 years, my laboratory investigated the physiological functions of neurotrophic factors, including neurotrophins, during development or post-injury and found that brain-derived neurotrophic factor (BDNF) plays a role in the formation of the laminar structure of the cerebral cortex. In addition, my laboratory discovered that endogenous glial cell line-derived neurotrophic factor (GDNF) contributes to the amelioration of motor activity after spinal cord injury. Therefore we aimed to develop low-molecular weight compounds that generate neurotrophic factor-like intracellular signals to protect or ameliorate neurological/psychiatric diseases. 2-Decenoic acid derivatives and other similar molecules could protect or ameliorate in animal models of mood disorders such as depression and enhance recovery from spinal cord injury-induced motor paralysis. Compounds that can generate neurotrophin-like signals in neurons are expected to be developed as therapeutic drugs for certain neurological or psychiatric disorders.