抄録
A large body of evidence has shown the involvement of serotonin (5-HT) in anxiety. Anxiety level appears to be correlated with brain 5-HT level. A selective serotonergic neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT), reduces brain 5-HT content, and produces anxiolytic effect when administered to adult rats. When a 5,7-DHT is administered to neonatal rats, it produces anxiogenic effect in elevated plus-maze test (Yamada & Iwasaki, 2002). In the elevated plus-maze test, passive avoidance of open platforms is the major index of anxiety, while in the defensive burying test, the major index of anxiety is the active burying of a spatially discrete shock-source. In the present study, we examined the effects of neonatal 5,7-DHT treatment on anxiety level in the defensive burying test. The results showed that neonatal 5,7-DHT treatment decreased 5-HT levels in cortex, hippocampus, and striatum, but increased in hypothalamus, midbrain, and medulla oblongata. In behavioral test, neonatal 5,7-DHT treatment decreased the latency to defensive burying and increased the duration of burying. These behavioral results suggest that the neonatal 5,7-DHT produces anxiogenic effect. The results demonstrate the differential effects of neonatal 5,7-DHT treatment on anxiety level and brain 5-HT system as compared with adult 5,7-DHT treatment.
