THE EFFECT OF BENZODIA ZEPINES ON THE STRESS-INDUCED RESPONSES OF THE NORA DRENERGIC A ND SEROTONERGIC PROJECTIONS TO THE RAT HIPPOCAMPUS

Microdialysis was used to measure the effect of benzodiazepines (BDZs) on basal levels and on stress-induced increases of 5 -hydroxytryptamine (5 -HT), 5 - hydroxyind oleacetic acid (5 -HIAA) , noradrenaline (NA), and dihydroxyphenylacetic acid (DOP AC). The stressors used were a 5 min tail pinch or a 10 min period of restraint. A subcutaneous injection of 5 mg/kg diazepam decreased basal levels of 5 -HT, 5 -HIAA, and DOPAC, but not NA. There was no effect on the stress-induced increase in 5 -HT, NA, and 5 -HIAA, while the increase in DOPAC was completely abolished. Local infusion of 5 µM flurazepam decteased the basal level of 5 - HT but not 5 -HIAA and abolished the stress-induced increase of 5 -HIAA but not 5 -HT. These results suggest that the anxiolytic action of BDZs is unlikely to be attributable to the suppression of stress-induced increases in the release of NA or 5 -HT in the hippocampus.