Objective To evaluate the role of the expression of protein kinase Cγ and Cα in spinal dorsal horn in the metabotropic glutamate receptor subtype 5 (mGluR5)'s participation in the development of morphine tolerance in rats. Methods Thirty-two male SD rats in which the intrathecal (IT) catheter was successfully placed were randomly divided into 4 groups (n = 8 each): control group (group C), morphine tolerance group (group M), antisense oligodeoxynucleotide (ODN) plus morphine group (group ANT) and mismatch ODN plus morphine group (group MIS). Rats in group M received 0.9% normal saline (NS) 5 μl twice a day for 8 days, and IT morphine 15 μg was injected simultaneously at 6, 7 and 8 days twice a day. Rats in group ANT and MIS received IT antisense and mismatch ODN 30 nmol (in 0.9% NS 5 μl) twice a day for 8 days respectively and IT morphine 15 μg was injected simultaneously at 6, 7 and 8 days twice a day. Rats in group C received NS instead twice a day for 8 days. Paw-withdrawl threshold (PWT) to thermal and mechanical stimulation was measured at 6, 7 and 8 days after ODN injection (T1-3). The animals were killed on 9th day (T4) and the lumbar segment of the spinal cord was removed for determination of the expression of mGluR5, PKCα and PKCγ mRNA (by RT-PCR), PKCαand PKCγ ( by Western blot). Results PWT to thermal and mechanical stimulation was significantly higher at T1.2in group M and MIS and at T1.3 in group ANT, the expression of mGluR5 mRNA, PKCα and PKCγ was significantly higher at T4 in group M and MIS, and mGluR5 mRNA expression was significantly lower at T4 in group ANT than in group C ( P ＜ 0.05). PWT to thermal and mechanical stimulation was significantly higher at T2.3, while the expression of mGluR5 mRNA, PKCα and PKCγ lower at T4 in group ANT than in group M ( P ＜ 0.05). Conclusion The expression of protein kinase C in spinal dorsal horn plays an important role in the mGluR5's participation in the development of morphine tolerance in rats.

Activation of inflammatory responses regulates the transmission of pain pathways through an integrated network in the peripheral and central nervous systems. The immunopotentiator thymosin alpha-1 (Tα1) has recently been reported to have anti-inflammatory and neuroprotective functions in rodents. However, how Tα1 affects inflammatory pain remains unclear. In the present study, intraperitoneal injection of Tα1 attenuated complete Freund's adjuvant (CFA)-induced pain hypersensitivity, and decreased the up-regulation of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in inflamed skin and the spinal cord. We found that CFA-induced peripheral inflammation evoked strong microglial activation, but the effect was reversed by Tα1. Notably, Tα1 reversed the CFA-induced up-regulation of vesicular glutamate transporter (VGLUT) and down-regulated the vesicular γ-aminobutyric acid transporter (VGAT) in the spinal cord. Taken together, these results suggest that Tα1 plays a therapeutic role in inflammatory pain and in the modulation of microglia-induced pro-inflammatory cytokine production in addition to mediation of VGLUT and VGAT expression in the spinal cord.

Rho-associated kinases (ROCKs) are serine-threonine protein kinases that act downstream of small Rho GTPases to regulate the dynamics of the actin cytoskeleton. Two ROCK isoforms (ROCK1 and ROCK2) are expressed in the mammalian central nervous system. Although ROCK activity has been implicated in synapse formation, whether the distinct ROCK isoforms have different roles in synapse formation and function in vivo is not clear. Here, we used a genetic approach to address this long-standing question. Both Rock1 and Rock2 mice had impaired glutamatergic transmission, reduced spine density, and fewer excitatory synapses in hippocampal CA1 pyramidal neurons. In addition, both Rock1 and Rock2 mice showed deficits in long-term potentiation at hippocampal CA1 synapses and were impaired in spatial learning and memory based on the water maze and contextual fear conditioning tests. However, the spine morphology of CA1 pyramidal neurons was altered only in Rock2 but not Rock1 mice. In this study we compared the roles of ROCK1 and ROCK2 in synapse formation and function in vivo for the first time. Our results provide a better understanding of the functions of distinct ROCK isoforms in synapse formation and function.