Disruptive influence of XXXX depletion on sensory preconditioning, but not first-order conditioning, in preweanling @entity35 .

@entity25410 @entity1063 @entity35
Learning and memory processes are known to be influenced by the action of @entity1063 (NE). The present study evaluated the influence of neonatal administration of the NE neurotoxin @entity25410 on sensory preconditioning (SPC) in 16- and 28-day-old @entity35 . @entity35 were subcutaneously administered 50 mg/kg @entity25410 or saline within 24 h after birth and tested at 16 or 28 days in two experiments. The results from Experiment 1 indicated that nondepleted 16-day-old @entity35 exhibited strong SPC, whereas this conditioning was disrupted by neonatal administration of @entity25410 . No SPC was seen in either neonatal treatment group at 28 days of age, confirming previous reports of an ontogenetic decline in SPC. In Experiment 2, no effects of @entity25410 were observed on first-order conditioning at either age. The brains of representative subjects were separated into forebrain, cerebellum, and brain stem samples and were analyzed to determine the extent of NE depletion. This analysis showed that @entity25410 produced a marked reduction in NE concentration in the forebrain, but not in the cerebellum or brain stem. The results of this study suggest a role for forebrain NE in SPC in preweanling @entity35 . This modulatory noradrenergic influence appears to be exerted on the formation of associations between two relatively neutral stimuli during the preexposure phase, given the absence of an effect of @entity25410 on primary conditioning.
