Transgenic mice expressing nerve growth factor in smooth muscle cells.

Ectopic expression of nerve growth factor (NGF) in transgenic mice leads to site-specific sympathetic sprouting. Smooth muscle cells in the intestines, urinary bladder, and arteries have been shown to express NGF. To address whether enhanced NGF production among these different organ systems stimulates comparable patterns of sympathetic collateral growth, we generated transgenic mice that express NGF under the control of the smooth muscle alpha-actin promoter. In response to elevated levels of NGF protein in the colon, bladder, and arteries/arterioles, sympathetic axons displayed robust sprouting only in the colon and bladder. These data reveal that, unlike most other peripheral tissues, sympathetic efferents in adult mammalian arteries/arterioles do not undergo collateral growth in response to increased levels of smooth muscle-derived NGF.