Increased branching of basal dendrites on pyramidal neurons in the occipital cortex of homozygous Brattleboro rats in standard and enriched environmental conditions: A Golgi study

Abstract As a continuation of our previous reports in a series of studies on the brain of Brattleboro rats, the branching of basal dendrites of pyramidal neurons in the upper layers of the occipital cortex was quantified in three groups of male heterozygous and homozygous Brattleboro rats. One group raised in standard environmental conditions was killed at 60 days of age, and another from standard conditions was killed at 90 days of age. A third group from enriched environmental conditions was killed at 90 days of age after 30 days of enrichment. Comparing the two types of Brattleboro rats, the homozygous rats showed significantly more total dendritic branching segments per neuron in both the 60-day-old standard condition group and the 90-day-old enriched group. A similar measure (segments per primary branch) was also significantly greater in homozygous than in heterozygous rats at 60 days of age. In the 90-day-old enriched group, the homozygous rats showed a trend toward more segments per primary branch than the heterozygous rats. The results suggest that the complete absence of vasopressin produces metabolic effects which, at certain ages or in certain environmental conditions, increase the branching of basal dendrites of pyramidal neurons in the upper layers of the occipital cortex.

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