Protective effect of recombinant human somatotropin on amyloid β-peptide induced learning and memory deficits in mice

This study aimed to examine the effects of the recombinant human somatotropin (rhGH) on protecting neuronal function, and improving learning and memory deficits in mice. Mice were intracerebroventricularly (icv) injected with the aggregated amyloid β-peptide (Aβ) to mimic the Alzheimer's disease (AD). The learning and memory functions in mice were examined by the step through test (an index of long-term memory) and the water maze performance (an index of spatial recognition memory). The results indicated that the mice treated with rhGH showed significant reduction of the error counts and the long memory retentions in the step-through test, and short swimming times in the water maze performance. Toxic effects of free radicals, damages of cholinergic neurons, and increased lipid peroxidation appeared in the cerebra of Aβ-treated mice, manifesting an increase of malondialdehyde (MDA) and decline of glutathione (GSH) level, an increment of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities, and a reduction of the acetylcholine (ACh) level. The gel electrophoresis pattern of the cerebra of mice treated with Aβ showed a typical DNA ladder of apoptosis. The in vivo experiments showed that the rhGH treatment significantly reversed the elevated MDA, ChAT, AChE, and the decreased GSH, ACh levels in the Aβ model mice. The results suggested that there were potential uses of the neuroprotective action of rhGH in the remedy of AD.