Hippocampal 72‐kDa heat shock protein expression varies according to mice learning performance independently from chronic exposure to stress

Abstract

The possibility that the inducible 72-kDa heat shock protein (hsp72) is involved in learning-related plasticity mechanisms was investigated in two inbred strains of mice that show spontaneous differences in spatial learning performance as well as an opposite reactivity to stress. Induction of hsp72 after radial maze training was measured by immunoblotting in the hippocampus of C57BL/6 (C57) and DBA/2 (DBA) inbred mice exposed or nonexposed to chronic acoustic stress. In agreement with previous studies, inter-strain differences in radial maze performance were found in nonstressed mice with C57 mice showing the higher scores. Chronic acoustic stress, however, impaired performance in the high-learner C57 strain and improved performance in the low-learner DBA strain. Western blot analysis revealed that post-training expression of hsp72 was low in the condition each strain was showing the higher-performance (nonstressed C57 and stressed DBA) and high in the condition each strain was showing the lower performance (stressed C57 and nonstressed DBA). These findings indicate that expression of hsp72 in the hippocampus varies as a function of the learning performance independently from exposure to chronic acoustic stress.

Heat Shock Protein 72 Overexpression Prevents Early Postoperative Memory Decline after Orthopedic Surgery under General Anesthesia in Mice

“…Hsp72 was previously shown to be lower in DBA mice that had learned a radial maze, but unchanged in C57Bl6 mice after learning the maze,29 while in contrast Heat Shock Cognate 70 was increased in rats learning the Morris water maze 28. The exact relationship between plasticity and expression levels of Hsp72 is thus not yet clear.…”

“…We have previously shown in animal and cell models of stroke that injury is reduced in animals or brain cells over-expressing Hsp7226 and that this is associated with reduced activation of the proinflammatory transcription Nuclear Factor κlight chain-enhancer of activated B cells (NFkB) 27. In addition to its roles in stress, survival and inflammation, Hsp72 has also been implicated in learning and plasticity, with upregulation of Heat Shock Cognate 70 reported in a learning paradigm28 and changes in Hsp72 noted in the hippocampus of animals trained in a radial maze task 29…”

The effects of acute 17β-estradiol treatment on gene expression in the young female mouse hippocampus

“…Hsp70-1 mRNA and protein levels are increased in the hippocampus of rats trained in the spatial Morris water maze (Pizarro et al, 2003), and the inducible form of Hsp70, Hsp72, is increased in the cerebellum during acquisition of a two-way avoidance task in rats (Ambrosini et al, 1999). Further, when Hsp72 is knocked out in mice, this deletion prevents spatial memory acquisition in the radial arm maze (Ambrosini et al, 2005), suggesting an active and potentially critical role for Hsp70 isoforms in learning and memory beyond their traditional function of simply complexing with ER in the cytoplasm and maintaining it in the inactive state.…”

System Level Mechanisms of Adaptation, Learning, Memory Formation and Evolvability: The Role of Chaperone and Other Networks

“…Both Hsp70 and Hsc70 levels increase during learning in the hippocampus [137][138][139]. The increased Hsp70 chaperone levels may be required for the increased protein synthesis of hippocampal neurons activated by the learning process.…”