It has been shown that the noradrenergic (NE) locus coeruleus (LC)-hippocampal pathway plays an important role in learning and memory processing, and that the development of this transmitter pathway is influenced by neurotrophic factors. Although some of these factors have been discovered, the regulartory mechanisms for this developmental event have not been fully elucidated. Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor influencing LC-NE neurons. We have utilized a GDNF knockout animal model to explore its functions on the LC-NE transmitter system during development, particularly with respect to target innervation. By transplanting various combinations of brainstem (including LC) and hippocampal tissue from wildtype or GDNF knockout fetuses into the brains of adult wildtype mice, we demonstrate that normal postnatal development of brainstem LC-NE neurons is disrupted as a result of the GDNF null mutation. Tyrosine hydroxylase immunohistochemistry reveal tht brainstem grafts had markedly reduced number and size of LC neurons in transplants from knockout fetuses. NE fiber innervation into the hippocampal co-transplant from an adjacent brainstem graft was also influenced by the presence of GDNF, with a significantly more robust innervation observed in transplants from wildtype fetuses. The most successful LC/hippocampal co-grafts were generated from fetuses expressing the wildtype GDNF background, whereas the most serverely affected transplants were derived from double transplants from null-mutated fetuses. Our data suggest that devloopment of the NE LC-hippocampal pathway is dependent on the present of GDNF, most likely through a target-derived neurotrophic function.
| Quintero, E M; Willis, L M; Zaman, V et al. (2004) Glial cell line-derived neurotrophic factor is essential for neuronal survival in the locus coeruleus-hippocampal noradrenergic pathway. Neuroscience 124:137-46 |
| Zaman, V; Li, Z; Middaugh, L et al. (2003) The noradrenergic system of aged GDNF heterozygous mice. Cell Transplant 12:291-303 |
