In the mature nervous system, cortical area 17 (primary visual cortex) receives afferent projections from the dorsal lateral geniculate nucleus and the cholinergic basal forebrain system. This project will use light and electron microscopic techniques in laboratory rats to study development of each projection system, and to study how the two systems may interact during development. Dr. Robertson and his colleagues have preliminary evidence suggesting that the geniculocortical system expresses acetylcholinesterase (AChE) transiently during the time when geniculocortical axons are invading the cortex and undergoing synaptogenesis with cortical neurons. The function of the transient AChE is unknown, but is of interest because: (1) it appears to serve as a reliable endogenous marker for developing geniculocortical axons, and (2) the presence of AChE suggests that the developing geniculocortical axons may interact with the developing cholinergic afferents from basal forebrain. Particular attention will be paid to time of arrival, laminar and areal patterns, and ultrastructural morphology of each afferent system. Possible interaction between the two afferent systems will be determined by studying the development of one system in the absence of the other. Possible functions of the transient AChE will be studied by determining the effect of AChE inhibition on development of normal morphology and by biochemical characterization of the transient AChE and its possible endogenous substrate. Dr. Robertson is an experienced neuroanatomist who has made substantial contributions to our knowledge of transient AChE expression in development. The results of these studies will provide new information about the formation of thalamocortical connections in the developing nervous system, and about the role of AChE in development.
