FUNCTIONAL CONSEQUENCES OF A SINGLE NERVE GROWTH-FACTOR ADMINISTRATION FOLLOWING SEPTAL DAMAGE IN RATS

This study examined how possible nerve growth factor (NGF)-induced beh aviour changes after septal damage might be modulated by the lesion ex tent, the dose of NGF administered and the delay between surgery and t he onset of testing. In a first experiment, young rats which received electrolytic septal lesions of high or low intensity (inducing respect ively large and mild iesions) were treated with 10 or 30 mug NGF admin istered intrahippocampally in a single injection. They were tested 4 m onths postoperatively for open field ambulation, spontaneous alternati on and radial maze performance. It was observed that irrespective of t he severity of the lesions rats were impaired in the spontaneous alter nation and radial maze tests; however, no obvious changes appeared in the open field test. While an NGF injection did not affect behavioural performances in rats with large lesions, it was capable of ameliorati ng behavioural deficits in the spontaneous alternation and radial maze tests of rats with mild lesions in both NGF dosage groups. It was als o seen that lesions produced a general decrease in hippocampal choline acetyltransferase (ChAT) activity, which was not significantly affect ed by an NGF administration. There was no significant correlation betw een ChAT activity and behavioural performance of NGF-treated rats. In a second experiment, young rats received mild septal lesions and were treated with 10 mug NGF. These rats were tested 2 weeks postoperativel y for radial maze performance. NGF rats exhibited similar behaviour to controls with regard to all of the variables measured. The present re sults suggest that a single NGF administration spares some abilities t o use spatial information efficiently providing lesions are partial.