Effects of differential environments on the cerebral anatomy of rats as a function of previous and subsequent housing conditions.
After 1 month in enriched or impoverished environments, groups of rats were housed for an additional month in either the same or the opposite environment. The cross-over design allowed us to see whether or not the cerebral effects of differential environments are modified by subsequent housing conditions, and also whether or not such effects might be influenced by previous experience. Differential housing for 1 month was associated with significant alterations in the weight and length of the cerebrum, the thickness of the occipital cortex, and the relative number of neurons and oligodendrocytes, and no change in the ratio of astrocytes to neurons. The effects of enrichment were not reduced in animals that were previously impoverished. When impoverishment followed enrichment, certain effects appeared to diminish, notably, the increase in cortical thickness. Other effects, however, such as the increase in the ratio of oligodendrocytes to neurons, were very stable. The gross cerebral alterations associated with differential housing did not differ significantly after 2 as opposed to 1 month's exposure, but the effects on neuronal density and the ratio of oligodendrocytes to neurons in layers V and VI of the cortex were, paradoxically, significantly smaller with the longer duration. We suggest that this decrease is due to the continuation of processes induced in the first month of differential experience rather than to their dissipation.
D000818:Animals; D001253:Astrocytes / Q000166:cytology; D002452:Cell Count; D006799:Housing, Animal; D008297:Male; D009474:Neurons / Q000166:cytology; D009778:Occipital Lobe / Q000166:cytology*; D009836:Oligodendroglia / Q000166:cytology; D051381:Rats / Q000502:physiology*; D011919:Rats, Inbred Strains