RATIONALE: Loss of telencephalic cholinergic projections has been postulated to contribute significantly to the cognitive decline associated with aging and dementia.
OBJECTIVE: The effects of the nicotinic acetylcholine receptor agonist ABT-418, a potential therapeutic drug for the treatment of the age- and dementia-associated cognitive disorders, were tested in an animal model of the cortical cholinergic deafferentation-induced impairments in sustained attention.
METHODS: Animals were trained in an operant task designed to test sustained attention performance. A partial loss of cortical cholinergic inputs was produced by infusions of 192 IgG-saporin into the basal forebrain. The effects of the systemic administration of ABT-418 (0.04, 0.13, 0.39 mg/kg) and the psychostimulant methylphenidate (0.2, 0.4, 0.8 mg/kg) were assessed.
RESULTS: Compared with sham-lesioned animals, this lesion resulted in a decrease in the relative number of hits while the relative number of correct rejections remained unaffected. Administration of ABT-418 significantly improved the relative number of hits. Furthermore, this effect of ABT-418 interacted with the effects of the lesion. Unexpectedly, this interaction was based on a significant enhancement of the performance of sham-lesioned animals while no effects were found in 192 IgG-saporin-lesioned animals. Administration of methylphenidate did not affect performance.
CONCLUSIONS: While these data do not support the hypothesis that administration of ABT-418 attenuates the impairments in attentional performance that result from loss of cortical cholinergic inputs, they support previous notions about this drug's ability to enhance cognitive processes in intact subjects.