Alterations in brain monoaminergic functioning associated with septal lesion induced hyperreactivity.

Thirty male albino rats, individually housed and receiving food and water ad lib were rated on 3 consecutive days for reactivity to handling. The animals were then assigned to behaviorally equivalent groups and received either bilateral septal lesions or a sham operation. Following two days of recovery, all animals received an additional behavioral testing session. Immediately following this last test, norepinephrine (NE) and dopamine (DA) levels, instantaneous rate constants (k), turnover times (TT) and utilization rates (K) as well as the levels of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in the hypothalamus, limbic system, cortex and pons-medulla were determined fluorometrically. Postoperatively, animals with septal lesions were significantly more reactive to handling, while the behavior of sham-operated controls remained essentially unchanged. Significant reductions in hypothalamic NE and DA and limbic DA were observed in the septal lesion animals. Catecholamine levels in other brain parts were unaffected as were 5-HT and 5-HIAA levels in all brain areas. Ratios of NE/5-HT in the limbic system were significantly reduced in animals which received septal lesions. Measures of catecholamine dynamics (k, TT, K) were unaltered by septal lesions. These results support the hypothesis of a catecholaminergic involvement in affective behavior but do not demonstrate any alteration in the functional dynamics of the brain monoamines associated with the hyperreactivity induced by septal lesions.