Shown is a superior cervical ganglion explant grown in the presence of Nerve Growth Factor (NGF). Synmpathetic neurons require NGF for growth and survival in vivo and in vitro. Our lab uses cultured sympathetic neurons to study the mechanism of action of NGF, the prototypic target-derived growth factor (For recent example, see Lonze et al., Neuron, 34:371-385, 2002).