BEHAVIORAL AND NEUROCHEMICAL EFFECTS OF SUPERIOR CERVICAL GANGLIONECTOMY IN RATS WITH SEPTOHIPPOCAMPAL LESIONS

This longitudinal study, extending over 12 months, assessed the behavi oural and biochemical effects of hippocampal sympathetic ingrowth (HSI ) into the partially denervated hippocampus. Male Long-Evans rats rece ived fimbria-fornix lesions (FIFO) or sham operations at 90 days of ag e. At the same time half of the rats from each group sustained bilater al ablation of the superior cervical ganglia (SCGX). A battery of beha vioural tests, measuring spontaneous alternation, activity in the open field and home cage, and radial-maze performance, were employed, star ting after one very short (16 days) and one extended (216 days) postop erative delay. Neurochemical analyses measuring choline acetyltransfer ase (ChAT) activity, high-affinity choline (HACU) and noradrenaline up take by hippocampal synaptosomes (HANU), hippocampal noradrenaline ([N A]), serotonin ([5-HT]) and 5-hydroxyindoleacetic acid ([5-HIAA]) conc entrations were carried out in a dorsal, a ''middle'' and a ventral re gion of the hippocampus. Lesion of the FIFO induced a significant and enduring deficit in radial-maze performance, in addition to a persiste nt locomotor hyperactivity. ChAT and HACU were significantly depleted in all three regions of the hippocampus at 12 months, and these defici ts were negatively correlated with maze performance. SCGX in the prese nce of the FIFO lesion significantly reduced [NA] in the middle region of the hippocampus, as compared to SCGX rats, and contributed to a re storation of lesion-induced depletions in [5-HT] and [5-HIAA] in the m iddle and ventral hippocampal regions, whilst failing to elicit any be havioural changes at either time point. It is concluded that if lesion -induced HSI indeed occurred, as is suggested by neurochemical evidenc e, it had no effect upon the observed behavioural deficits elicited by transection of the FIFO in the rat.