PHENOTYPIC CHARACTERIZATION OF RESPECIFIED VISUAL-CORTEX SUBSEQUENT TO PRENATAL ENUCLEATION IN THE MONKEY - DEVELOPMENT OF ACETYLCHOLINESTERASE AND CYTOCHROME-OXIDASE PATTERNS

Prenatal bilateral enucleation induces cortex, which normally would ha ve become striate cortex, to follow a default developmental pathway an d to take on the cytoarchitectonic appearance of extrastriate cortex ( default extrastriate cortex, Dehay et al. [1996] J. Comp. Neurol. 367: 70-89). We have investigated if this manipulation influences the corti cal expression of acetylcholinesterase (AChE) and cytochrome oxidase ( CO). Early enucleation (before embryonic day 81; E81) had only minor e ffects on the distribution of AChE and CO in the striate cortex. In an imals that underwent operation, the striate cortex CO blobs were signi ficantly more closely spaced on the operculum compared with the calcar ine. After early enucleation, there was a periodic distribution of CO dense patches in default extrastriate cortex. These CO patches had a c enter-to-center spacing that was considerably smaller than that of CO stripes in normal area V2, but was somewhat larger than that of the CO blobs in striate cortex. Although the CO stripes characteristic of no rmal area V2 could not be detected, there were some high-frequency CO patches, similar to those found in default extrastriate cortex. Early enucleation caused a failure to form the transient AChE bands running perpendicular to the striate border, which are normally present in the fetus and early neonate. Late enucleation did not alter AChE expressi on in extrastriate cortex. The relatively minor effects of early enucl eation in the reduced striate cortex contrast with the changes in expr ession of these enzymes in extrastriate cortex, which accompany large shifts in the location of the striate border. This suggests a massive reorganisation of cortical phenotype in extrastriate cortex. (C) 1996 Wiley-Liss, Inc.