Molecular chaperone heat shock protein 70 participates in the labile phase of the development of behavioural sensitization induced by a single morphine exposure in mice

Abstract

De-novo protein synthesis is required in the development of behavioural sensitization. A prior screening test from our laboratory has implicated heat shock protein 70 (Hsp70) as one of the proteins required in this behavioural plasticity. Thus, this study was designed to extend our understanding of the role of Hsp70 in the development of behavioural sensitization induced by a single morphine exposure in mice. First, by employing transcription inhibitor actinomycin D (AD) and protein synthesis inhibitor cycloheximide (CHX), we identified a protein synthesis-dependent labile phase (within 4 h after the first morphine injection) in the development of behavioural sensitization to a single morphine exposure. Second, Hsp70 protein expression in the nucleus accumbens correlated positively with locomotor responses of sensitized mice and, more importantly, the expression of Hsp70 increased within 1 h after the first morphine injection. Third, AD and CHX both prevented expression of Hsp70 and disrupted the development of the single morphine induced behavioural sensitization, which further implied Hsp70 was highly associated with behavioural sensitization. Finally, the selective Hsp70 inhibitor pifithrin-μ (PES) i.c.v. injected in mice prevented the development of behavioural sensitization and, critically, this inhibitory effect occurred only when PES was given within 1 h after the first morphine injection, which was within the labile phase of the development period. Taken together, we draw the conclusion that Hsp70 is crucially involved in the labile phase of the development of behavioural sensitization induced by a single morphine exposure, probably functioning as a molecular chaperone.

Activation of neuronal Kv7/KCNQ/M-channels by the opener QO58-lysine and its anti-nociceptive effects on inflammatory pain in rodents

“…Horizontal locomotor activity was recorded with a video camera placed above the chamber and analyzed with Digbehv software (version 2.0, Shanghai Jiliang Software Technology Co Ltd, China) [13,24] . Mice were individually placed in a cage for 10 min to allow for adaptation to the new environment.…”

Chaperone heat shock protein 70 in nucleus accumbens core: a novel biological target of behavioural sensitization to morphine in rats

“…The detailed steps for preparation of homogenates and western blot analysis were described in a previous paper (Qin et al, 2013).…”

“…So far, there has been no report about Hsp70's direct role in drug addiction. Our previously reported work was the first to associate chaperone Hsp70 with drug-induced behavioural sensitization Qin et al, 2013). Therefore, we targeted the NAc core and shell to investigate a possible mutual relationship between Hsp70 and single morphine-induced behavioural sensitization in rats.…”

“…Traditionally, behavioural sensitization was induced by repeated, intermittent drug exposures. Amazingly, even a single drug exposure, such as an exposure to amphetamine (Robinson et al, 1982;Vanderschuren et al, 1999), cocaine (Kalivas and Alesdatter, 1993), morphine (Vanderschuren et al, 2001;Jing et al, 2011;Luo et al, 2011;Qin et al, 2013) and nicotine (Bhatti et al, 2007) can also evoke behavioural sensitization. Although the extent of behavioural sensitization induced by a single drug exposure is not as profound as that induced by multiple drug exposures, the enduring behavioural and neurochemical consequences of single and repeated drug exposures appear to be highly comparable (Vanderschuren et al, 2001).…”

“…The chaperones participating broadly in de novo protein folding and refolding are mainly Hsp70s, Hsp90s and the chaperonins (Hsp60s) (Hartl et al, 2011). Recently, we have demonstrated that chaperone Hsp70, one of the most important members of the Hsp70s, is dynamically involved in the labile phase of the development of behavioural sensitization to a single morphine exposure in mice (Qin et al, 2013). The structure of Hsp70 (also called HspA1A) contains three domains, a highly conserved N-terminal nucleotide-binding domain that has ATPase activity (NBD), a protein peptide substratebinding domain (SBD), and a poorly conserved C-terminal domain terminating with an EEVD motif (Brodsky and Chiosis, 2006;Daugaard et al, 2007;Patury et al, 2009).…”