Gene expression analysis of heat shock proteins in the nucleus accumbens of rats with different morphine seeking behaviours

Heat-shock proteins play functional roles on brain regulatory processes which are deeply involved in drug addiction, such as synaptic plasticity. However, few studies have been focused on gene expression of heat-shock proteins (Hsp) as potential diagnostic tools for addiction risk. This work tries to provide new knowledge on this field by using two rat models of differential vulnerability to morphine addiction in order to study differential gene expression of a selected group of Hsp genes in the nucleus accumbens (NAc). Hsp70-1A, 84, 86 and 105 genes were similarly regulated by an acute injection of morphine in two subpopulations of Sprague Dawley (SD) rats showing different rates of extinction of morphine conditioned preference. However, Lewis and Fischer rats, two strains that differ in many aspects of drug seeking behaviours, exhibited marked differences in their expression patterns of Hsp84, 86 and 105. These results suggest that differential Hsp gene expression could be related to addiction vulnerability and recommend further work to validate these proteins as potential markers for drug addiction risk.

► Individual differences on morphine addiction vulnerability were established.
► Sprague–Dawley CPP paradigm and F344–Lewis rats were used.
► We focused on the differential expression of Hsps in the nucleus accumbens.
► Lewis and F344 rats show marked differences in Hsp84, 86 and 105 expression patterns.
► Morphine down-regulates Hsps in Sprague Dawley, despite individual differences in CPP.