Recovery from infant medial frontal cortical lesions in rats is reversed by cortical lesions in adulthood.
Previous studies have shown that when the medial prefrontal cortex (mPFC) is removed at 7-10 days of age there is a spontaneous filling of the lesion cavity and a nearly complete restitution of behaviour. In the current study animals received mPFC lesions on postnatal day 10 and on day 160 the tissue occupying the mPFC region was again removed. Behavioural performance on the Morris water task was compared to animals with either only day 10 mPFC lesions or only day 160 mPFC lesions. Rats with the combined day 10 and day 160 lesions or day 160 lesions were severely impaired at the task whereas the rats with only day 10 lesions showed complete recovery. An analysis of dendritic arborization in pyramidal neurons adjacent to the lesion showed increased dendritic arborization in the basilar fields in both the P10 groups but this was not associated with functional recovery in the animals with the two mPFC lesions. It thus appears that the tissue that filled in the mPFC lesions on day 10 was functional.
Dallison
Agnes
A
Canadian Centre for Behavioural Neuroscience, University of Lethbridge, Lethbridge, AB, Canada, T1K 3M4.
Kolb
Bryan
B
D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal / Q000502:physiology*; D003712:Dendrites / Q000473:pathology; D004924:Escape Reaction / Q000502:physiology; D005260:Female; D008297:Male; D018782:Maze Learning / Q000502:physiology; D009929:Organ Size; D017397:Prefrontal Cortex / Q000254:growth & development / Q000473:pathology*; D051381:Rats; D020318:Rats, Long-Evans; D020127:Recovery of Function; D012737:Sex Factors; D016622:Silver Staining / Q000379:methods; D013550:Swimming / Q000502:physiology; D013997:Time Factors