Region- or state-related differences in expression and activation of extracellular signal-regulated kinases (ERKs) in naïve and pain-experiencing rats.

BACKGROUND: Extracellular signal-regulated kinase (ERK), one member of the mitogen-activated protein kinase (MAPK) family, has been suggested to regulate a diverse array of cellular functions, including cell growth, differentiation, survival, as well as neuronal plasticity. Recent evidence indicates a role for ERKs in nociceptive processing in both dorsal root ganglion and spinal cord. However, little literature has been reported to examine the differential distribution and activation of ERK isoforms, ERK1 and ERK2, at different levels of pain-related pathways under both normal and pain states. In the present study, quantitative blot immunolabeling technique was used to determine the spatial and temporal expression of ERK1 and ERK2, as well as their activated forms, in the spinal cord, primary somatosensory cortex (SI area of cortex), and hippocampus under normal, transient pain and persistent pain states. RESULTS: In naïve rats, we detected regional differences in total expression of ERK1 and ERK2 across different areas. In the spinal cord, ERK1 was expressed more abundantly than ERK2, while in the SI area of cortex and hippocampus, there was a larger amount of ERK2 than ERK1. Moreover, phosphorylated ERK2 (pERK2), not phosphorylated ERK1 (pERK1), was normally expressed with a high level in the SI area and hippocampus, but both pERK1 and pERK2 were barely detectable in normal spinal cord. Intraplantar saline or bee venom injection, mimicking transient or persistent pain respectively, can equally initiate an intense and long-lasting activation of ERKs in all three areas examined. However, isoform-dependent differences existed among these areas, that is, pERK2 exhibited stronger response than pERK1 in the spinal cord, whereas ERK1 was more remarkably activated than ERK2 in the S1 area and hippocampus. CONCLUSION: Taken these results together, we conclude that: (1) under normal state, while ERK immunoreactivity is broadly distributed in the rat central nervous system in general, the relative abundance of ERK1 and ERK2 differs greatly among specific regions; (2) under pain state, either ERK1 or ERK2 can be effectively phosphorylated with a long-term duration by both transient and persistent pain, but their response patterns differ from each other across distinct regions; (3) The long-lasting ERKs activation induced by bee venom injection is highly correlated with our previous behavioral, electrophysiological, morphological and pharmacological observations, lending further support to the functional importance of ERKs-mediated signaling pathways in the processing of negative consequences of pain associated with sensory, emotional and cognitive dimensions.

Phosphorylation of c-Jun N-terminal kinase isoforms and their different roles in spinal cord dorsal horn and primary somatosensory cortex.

The present study was undertaken to investigate whether isoforms of c-Jun N-terminal kinase (JNK 46 kDa and 54 kDa), one component of the mitogen-activated protein kinase (MAPK) family, might show region-related differential activation patterns in both naïve and pain-experiencing rats. In naïve rats, no significant difference was observed in total expression level of the two JNK isoforms between spinal cord and primary somatosensory cortex (S1 area). However, phosphorylated JNK 46 kDa was normally expressed in the S1 area, but not in the spinal cord, while neither of the two structures contained phosphorylated JNK 54 kDa. Subcutaneous bee venom (BV)-induced persistent pain stimulation resulted in a significant increase in the phosphorylation of both JNK isoforms in each area for a long period (lasting at least 48 h). Nevertheless, JNK 46 kDa exhibited a much higher activation than JNK 54 kDa in the spinal cord, whereas the same noxious stimulation elicited evident activation of JNK 54 kDa in the S1 area, leaving JNK 46 kDa less affected. Intraplantar injection of sterile saline solution, causing acute and transient pain, produced almost the same changes in activation profile of the two JNK isoforms as found in the BV-treated rats. These results implicate that individual members of the JNK family may be associated with specific regions of nociceptive processing. Also, the two JNK isoforms are supposed to function differently according to their locations within the rat central nervous system.

[Isopotential map of somatosensory evoked potential and motor revoked potential in spinal cord: an experimental study].

OBJECTIVE: To investigate the distribution of conduction pathways of somtosensory evoked potential (SEP) and motor evoked potential (MEP) in the spinal cord. METHODS: Twenty-five Wistar rats underwent operation to expose the left sciatic nerve and sphenotresia. The sciatic nerve and sensory-motor cortex of 10 rats were stimulated so as to induce MEP and SEP. Different stimulating parameters were used to record their influence on MEP and SEP. Then the microelectrode was removed to a new place 1 cm from the original place and the maximum MEP and maximum SEP were recorded so as to calculate the conduction speeds of MEP and SEP. A microelectrode was put to the ventral side of spinal cord of 15 rats so as to record the isopotential map of MEP and SEP in the spinal cord. RESULTS: The Ni-P1 of SEP increased when the microelectrode was moved from the anterior side to the posterior side and the change was more prominent in the anterior funiculus area. The N2-P2 decreased when the microelectrode was moved from anterior side to posterior side, and the change was more prominent in the posterior funiculus area. CONCLUSION: SEP is mainly conducted in the posterior tracts and MEP in the anterior tracts. MEP may originate from extra-pyramid system.

Effects of six selected antibiotics on plant growth and soil microbial and enzymatic activities.

The potential impact of six antibiotics (chlortetracycline, tetracycline and tylosin; sulfamethoxazole, sulfamethazine and trimethoprim) on plant growth and soil quality was studied by using seed germination test on filter paper and plant growth test in soil, soil respiration and phosphatase activity tests. The phytotoxic effects varied between the antibiotics and between plant species (sweet oat, rice and cucumber). Rice was most sensitive to sulfamethoxazole with the EC10 value of 0.1 mg/L. The antibiotics tested inhibited soil phosphatase activity during the 22 days' incubation. Significant effects on soil respiration were found for the two sulfonamides (sulfamethoxazole and sulfamethazine) and trimethoprim, whereas little effects were observed for the two tetracyclines and tylosin. The effective concentrations (EC10 values) for soil respiration in the first 2 days were 7 mg/kg for sulfamethoxazole, 13 mg/kg for sulfamethazine and 20 mg/kg for trimethoprim. Antibiotic residues in manure and soils may affect soil microbial and enzyme activities.

[Brain mechanisms of hypoxic preconditioning].

A Review: A concept of tissue adaptation to hypoxia (i. e. hypoxic preconditioning) was developed and its corresponding animal models were reproduced in 1966s. The methods of model reproduction in rat, rabbit, and mouse in particular and the main results are briefly introduced in this review. The tolerance to hypoxia of preconditioned animals is significantly increased. Regular changes in animals' behavior, neurophysiology, respiratory and circulatory physiology, neuron morphology in vivo and function of brain and spinal cord in vitro are briefly demonstrated. The protective effects in vivo and in vitro of homogenate extract taken from the brain of preconditioned animals, neurochemicals and molecular neurobiological alterations are briefly presented. The essence and significance of tissue adaptation to hypoxia/hypoxic preconditioning are discussed in the review in terms of evolution and practical implication.