Impairment of learning and memory in shuttle box-trained rats neonatally injected with 6-hydroxydopamine. Effects of nootropic drugs.

The effect of neonatal 6-hydroxydopamine (6-OHDA) treatment on learning and retention and on the level of biogenic monoamines in some brain structures as well as the influence of the nootropic drugs--piracetam, aniracetam, meclofenoxate and fipexide on the 6-OHDA-induced effect was studied. Two- way active avoidance (shuttle box) was used. The levels of noradrenaline (NA), dopamine (DA) and serotonin (5-HT) in the frontal cortex, striatum, hypothalamus, hippocampus and pons were measured. In mature rats, injected with 6-OHDA (100 mg/kg s.c.) in the first 3 postnatal days learning and retention were impaired and the NA level in the frontal cortex and hippocampus was decreased. Piracetam (600 mg/kg), aniracetam (50 mg/kg), meclofenoxate (100 mg/kg) and fipexide (10 mg/kg) administered orally 5 days before and 5 days during training, abolished the amnestic effect of 6-OHDA and restored to control values the NA level in the frontal cortex and hippocampus. This finding suggests the important role of the noradrenergic neurotransmitter system in the 6-OHDA-induced amnesia, as well as in the favorable effect of the nootropic drugs tested on 6-OHDA-impaired memory processes.