Sex differences in dendritic response to differential experience in the rat visual cortex.

Male and female hooded rats were raised from weaning in either a complex or an isolated environment. After one month, the visual cortex was Golgi-Cox-stained and layers III and V pyramidal and layer IV stellate neurons were quantified: (1) analyses of dendritic branch numbers and total dendritic length revealed that females exhibited smaller differences in response to the rearing environment than males in both apical oblique and basilar branches of layer III pyramidal neurons; (2) a similar but much weaker trend towards a sex by environment interaction was seen in layer IV stellate neurons, while in layer V pyramidal neurons the sexes showed equal amounts of dendritic response; (3) the terminal dendrites in every cell population were longer in the rats from the complex environment regardless of sex; (4) males had longer terminal branches in both environments in layer IV stellates and layer V lower apical oblique branches. Thus the sex differences that appeared across environments were small. The more prominent sex differences were seen when the rearing environment was varied, with females showing less susceptibility to environmental influences in some neuronal populations.