Acute Hypervolemic Infusion Can Improve Splanchnic Perfusion in Elderly Patients During Laparoscopic Colorectal Surgery.

BACKGROUND There is no adequate evidence on how the long duration of laparoscopic surgery affects splanchnic perfusion in elderly patients or the efficacy of acute hypervolemic fluid infusion (AHFI) during the induction of anesthesia. Our aim was to observe the effects of AHFI during the induction of general anesthesia on splanchnic perfusion. MATERIAL AND METHODS Seventy elderly patients receiving laparoscopic colorectal surgery were randomly divided into three groups: lactated Ringer's solution group (group R), succinylated gelatin group (group G), and hypertonic sodium chloride hydroxyethyl starch 40 injection group (group H). Thirty minutes after the induction of general anesthesia, patients received an infusion of target dose of these three solutions. Corresponding hemodynamic parameters, arterial blood gas analysis, and gastric mucosal carbon dioxide tension were monitored in sequences. RESULTS In all three groups, gastric-arterial partial CO2 pressure gaps (Pg-aCO2) were decreased at several beginning stages and then gradually increased, Pg-aCO2 also varied between groups due to certain time points. The pH values of gastric mucosa (pHi) decreased gradually after the induction of pneumoperitoneum in the three groups. CONCLUSIONS The AHFI of succinylated gelatin (12 ml/kg) during the induction of anesthesia can improve splanchnic perfusion in elderly patients undergoing laparoscopic surgery for colorectal cancer and maintain good splanchnic perfusion even after a long period of pneumoperitoneum (60 minutes). AHFI can improve splanchnic perfusion in elderly patients undergoing laparoscopic colorectal surgery.

The ventrolateral preoptic nucleus is required for propofol-induced inhibition of locus coeruleus neuronal activity.

The mechanisms underlying the unconsciousness of general anesthesia are not completely understood. Accumulating evidence indicates the ventrolateral preoptic nucleus (VLPO) in the endogenous sleep circuits may contribute to loss of consciousness (LOC) induced by GABA-enhancing anesthetics. However, there are few studies that look into distinct sleep pathway in the sleep-wake system. In the neural pathway from VLPO to the locus coeruleus (LC), we compared the inhibition effect of propofol on the LC activity before and after VLPO lesion in vivo rats. Systemic administration of propofol (20 mg/kg, i.p.) in normal rats caused a fast and obvious inhibition of LC neurons spontaneous firing (from 0.24 ± 0.06 to 0.12 ± 0.03 Hz). The LC neuronal firing rate of VLPO lesion rats only decreased to 0.18 ± 0.05 Hz (P = 0.021 vs. non-VLPO rats) after the propofol injection, and the time to reach the maximal inhibition level was also prolonged in VLPO lesion rats (2.3 ± 0.7 vs. 5.8 ± 1.2 min, P = 0.037). Microinjections of a selective GABAA receptor antagonist (SR95531) into the LC fully reversed the inhibitory effect of propofol on the LC neuronal activity, but did not significantly affect the latency to loss of righting reflex of rats after propofol administration (3.4 ± 0.9 vs. 3.7 ± 1.2 min, P = 0.639). Our results indicated that VLPO is necessary for the propofol-induced inhibition of LC activity, but the LC may not play an important role in the propofol-induced LOC.

Anesthetic effects of propofol in the healthy human brain: functional imaging evidence.

Functional imaging methods, including positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), have become important tools for studying how anesthetic drugs act in the human brain to induce the state of general anesthesia. Recent imaging studies using fMRI and PET techniques have demonstrated the regional effects of propofol on the brain. However, the pharmacological mechanism of the action of propofol in the intact human central nervous system is unclear. To explore the possible action targets of propofol in the human brain, a systematic review of the literature was performed. The literature search was performed with limiting factors of "propofol," "functional imaging," "positron emission tomography", and "functional magnetic resonance imaging" from 1966 to July 2013 (using Medline, EMBASE, CINAHL and hand searches of references). Studies meeting the inclusion criteria were reviewed and critiqued for the purpose of this literature research. Eighteen researches meeting the inclusion criteria were reviewed in terms of the appropriateness of valuation technique. In the unconscious state, propofol sharply reduces the regional glucose metabolism rate (rGMR) and regional cerebral blood flow (rCBF) in all brain regions, particularly in the thalamus. However, GMR, such as in the occipital, temporal, and frontal lobes, was obviously decreased at a sedative dosage of propofol, whereas, changes in the thalamus were not obvious. Using fMRI, several studies observed a decrease of connectivity of the thalamus versus an increase of connectivity within the pons of the brainstem during propofol-induced mild sedation. During deep sedation, propofol preserves cortical sensory reactivity, the specific thalamocortical network is moderately affected, whereas the nonspecific thalamocortical network is severely suppressed. In contrast, several recent fMRI studies are consistent on the systemic decreased effects of propofol in the frontoparietal network. Accumulating evidence suggest that propofol-induced unconsciousness is associated with a global metabolic and vascular depression in the human brain and especially with a significant reduction in the thalamocortical network and the frontoparietal network.

Post-training intra-basolateral amygdala infusions of norepinephrine block sevoflurane-induced impairment of memory consolidation and activity-regulated cytoskeletal protein expression inhibition in rat hippocampus.

Considerable evidence indicates that the noradrenergic system of the basolateral amygdala (BLA) participates in the consolidation of various types of emotionally arousing memories. We previously reported that administration of an anesthetic-dose of sevoflurane immediately after continuous multiple-trail inhibition avoidance (CMIA) training impaired memory consolidation. This experiment investigated whether posttraining noradrenergic activation of the BLA is sufficient to reverse the memory impairing effect of sevoflurane. Adult male Sprague-Dawley rats received bilateral injections of norepinephrine (NE 0.3, 1.0, or 3.0 µg/0.5 µl) or normal saline (NS 0.5 µl) immediately after training in a CMIA paradigm. Subsequently, the rats were exposed to sevoflurane (2% inspired) or air for 2h. Norepinephrine produced a dose-dependent enhancement of memory consolidation on a 24-h retention test. The highest dose of NE tested (3.0 µg/0.5 µl) blocked sevoflurane-induced impairment of memory consolidation and reversed the inhibitory effect of sevoflurane on activity-regulated cytoskeletal protein (Arc) expression in the hippocampus 2h after training. These findings provide evidence that the mechanism mediating the memory-impairing effect of sevoflurane involves a network interaction between the BLA noradrenergic system and modulation of Arc protein expression in the hippocampus.

Substance P Mediates Estrogen Modulation Proinflammatory Cytokines Release in Intervertebral Disc.

Intervertebral disc degeneration (IDD) is a main contributor to low back pain. A close relationship exists between inflammation and pain. Estrogen can affect inflammation and may play a crucial role in IDD and pain. Substance P (SP) can also regulate the expression of pro-inflammatory cytokines in intervertebral disc (IVD). This study aimed to investigate the potential role of SP in estrogen regulation of IDD. Nine-week-old C57BL/6 female mice were divided into four groups as follows: sham surgery (sham), ovariectomy (OVX), ovariectomy plus estrogen replacement therapy (ERT) group (OVX+E2), and ovariectomy, ERT plus neurokinin 1 receptor (NK1R) agonist (OVX+E2+G). Serum E2, body, and uterus weight were recorded. Immunohistochemistry study and quantitative real-time PCR were used for SP, NK1R, IL-1ß, IL-6, and TNF-α examination and comparison in IVD at protein and gene levels. After OVX, the gene and protein expression of TNF-α, IL-1ß, IL-6, SP, and NK1R in NP cells significantly increased compared with the sham group. ERT can reverse these impacts. ERT plays anti-inflammatory and anti-hyperalgesic roles in IDD of OVX mice. The estrogen-induced changes of the pro-inflammatory cytokines, TNF-α, IL-1ß, and IL-6, are significantly inhibited by NK1R agonists. SP may be a mediator of estrogen regulating pro-inflammatory factors in IDD. Estrogen may affect IVD inflammation through two ways: one is to directly affect the level of pro-inflammatory cytokines and the other is by means of modulation of SP.

Sevoflurane impairs memory consolidation in rats, possibly through inhibiting phosphorylation of glycogen synthase kinase-3ß in the hippocampus.

Sevoflurane administration impairs memory processes in both humans and animals. Increasing evidence suggests that enhancement of the phosphorylation state of glycogen synthase kinase-3ß (GSK-3ß), as a result of acute administration of lithium chloride (LiCl), may enhance memory consolidation. The current experiments examined whether GSK-3ß phosphorylation was involved in mediating the memory impairing effects of posttraining sevoflurane on inhibitory avoidance (IA) retention. In experiment 1, adult male Sprague-Dawley rats were exposed to sevoflurane (0.5%, 1%, or 2%) for 2h immediately after training in a continuous multiple-trail IA paradigm. Sevoflurane (2% inspired) induced significant impairment of retention performance on a 24-h test and inhibited phosphorylation of GSK-3ß in the hippocampus 2h after training. In experiment 2, administration of LiCl (100mg/kg, intraperitoneally) 30 min before IA training not only blocked the sevoflurane-induced impairment of consolidation, but also reversed the inhibitory effect of sevoflurane on GSK-3ß phosphorylation in the hippocampus. Collectively, these findings support the hypothesis that sevoflurane exposure can impair consolidation of IA memory in rats. Sevoflurane-induced amnesia may be due, at least in part, to suppression of GSK-3ß phosphorylation in the hippocampus.

Bilateral inhibition of gamma-aminobutyric acid type A receptor function within the basolateral amygdala blocked propofol-induced amnesia and activity-regulated cytoskeletal protein expression inhibition in the hippocampus.

BACKGROUND: It has been reported that bilateral lesions of the basolateral amygdala complex (BLA) blocked propofol-induced amnesia of inhibitory avoidance (IA) training. Based on these results, the authors hypothesized that the amnesia effect of propofol was partly due to its impairment of memory formation in the hippocampus through activating the BLA gamma-aminobutyric acid type A receptor function. The authors determined the changes in activity-regulated cytoskeleton-associated protein (Arc) expression to be an indicator of IA memory formation. METHODS: Male Sprague-Dawley rats received bilateral injection of bicuculline methiodide (10, 50, or 100 pmol/0.5 microl) or saline (0.5 microl) into the BLA. Fifteen minutes later, the rats were intraperitoneally injected with either propofol (25 mg/kg) or saline. After 5 min, the one-trial IA training was conducted. Rats intraperitoneally infused with saline served as controls and only received saline injections into the BLA. Twenty-four hours later, the IA retention latency was tested. Separate groups of rats treated the same way were killed either 30 min after IA training for hippocampal Arc mRNA measurement or after 45 min for protein level quantification. RESULTS: The largest dose of bicuculline methiodide (100 pmol) not only blocked the propofol-induced amnesia but also reversed the inhibition effect of propofol on Arc protein expression in the hippocampus (P < 0.05). However, the mRNA level of Arc showed no significant changes after propofol and bicuculline methiodide administration. CONCLUSIONS: The amnesic effect of propofol seems to involve the modulation of Arc protein expression in the hippocampus, occurring through a network interaction with the BLA.

Different doses of sevoflurane facilitate and impair learning and memory function through activation of the ERK pathway and synthesis of ARC protein in the rat hippocampus.

BACKGROUND: Sevoflurane has been shown to stimulate or depress memory in adult rats; however, the cellular mechanism of this bidirectional effect has not been fully investigated. METHODS: We used an intra-hippocampal microinfusion of U0126 to suppress ERK activation. Male SD rats were randomly assigned to four groups: Sham, 0.11%SEV, 0.3%SEV and 0.3%+U0126. They received bilateral injections of U0126 or saline. Rats were anesthetized, and Inhibitory Avoidance (IA) training was performed immediately after anesthesia. The memory retention latency was observed 24 h later. In another experiment, the hippocampus was removed 45 min after IA training to assess ARC expression, the synapsin 1 protein levels and the phosphorylation level of ERK. RESULTS: Treatment with 0.11%SEV led to rapid phosphorylation of ERK, while 0.3%SEV inhibited phosphorylation; the latter change was reversed by the microinfusion of U0126 in the hippocampus. The memory latency result had similar tendencies. The local infusion of U0126 abolished the 0.3%SEV-induced memory impairment and ERK inhibition. Selective upregulations of ARC and synapsin 1 proteins were observed in the 0.3%SEV group compared with the 0.11%SEV group. CONCLUSIONS: The results indicate that different doses of sevoflurane trigger synaptic plasticity-related cytoskeleton proteins through the ERK signaling pathway. This novel modulation by inhalational agents may help to reduce their side-effects on memory function.

Effects of Low Bone Mineral Status on Biomechanical Characteristics in Idiopathic Scoliotic Spinal Deformity.

BACKGROUND: Low bone mass in patients with adolescent idiopathic scoliosis has been well reported. Poor bone quality was regarded as a new and unique prognostic factor in aggravating curve progression. However, the potential biomechanical correlation between them remains unclear. METHODS: Three-dimensional finite element models of idiopathic scoliotic spine with different bone mineral status were created for axial loading simulation. An axial load of 3 different body weights was applied on different bone mineral mass models. The mechanical responses of the vertebral cortical and cancellous bone, facet joints, end plate, and intervertebral disc were analyzed. RESULTS: Accompanied with the low bone mineral status, thoracic scoliosis produced asymmetric and higher stress in the cortical bone, lumbar facet joints, and end plate at the concave side of the thoracic structure curve. Stress increased in the disc at the apex of the scoliosis, whereas it mildly decreased in the L4-5 and L5-S1 disc. Body weight gain increased the stress in scoliotic spine structures in all bone mineral statues. CONCLUSIONS: Biomechanical simulations indicated that low bone mineral mass might aggravate curve progression and induce more serious lumbar compensatory scoliosis in patients with adolescent idiopathic scoliosis. Weight gain was also a risk factor for curve progression.

Estrogen receptors involvement in intervertebral discogenic pain of the elderly women: colocalization and correlation with the expression of Substance P in nucleus pulposus.

Estrogenic modulation of pain is an exceedingly complex phenomenon. However, whether estrogen is involved in discogenic low back pain still remains unclear. Here, immunoreactivity staining technique was used to examine the expression level of the estrogen receptors (ERα and ERß) and a pain related neuropeptide, Substance P in the lumbar intervertebral discs to analyze the relationship between the ERs and Substance P. Nucleus pulposus tissues of 23 elderly female patients were harvested during spinal surgeries and made to detect the immunoreactivity staining of ERα, ERß and Substance P. The colocalization and intensities of ERs and Substance P were explored and evaluated respectively. The correlations between changes of ERα, ERß and Substance P were also assessed.Our results revealed that Substance P colocalized with ERα and ERß both in cytoplasm and nucleus of the nucleus pulposus cells. HSCORE analysis indicated that Substance P negatively correlated with both ERα and ERß expression. Collectively, the crosstalk between ERs and Substance P might exist in the disc tissue. Estrogen-dependent pain mechanism might partly be mediated through ERs and Substance P in the nucleus pulposus of the elderly females. Estrogen and its receptors might be drug targets in discogenic low back pain diseases.

Location- and Subunit-Specific NMDA Receptors Determine the Developmental Sevoflurane Neurotoxicity Through ERK1/2 Signaling.

It is well established that developmental exposure of sevoflurane (an inhalational anesthetic) is capable of inducing neuronal apoptosis and subsequent learning and memory disorders. Synaptic NMDA receptors activity plays an essential role in cell survival, while the extra-synaptic NMDA receptors activation is usually associated with cell death. However, whether synaptic or extra-synaptic NMDA receptors mediate developmental sevoflurane neurotoxicity is largely unknown. Here, we show that developmental sevoflurane treatment decreased NR2A, but increased NR2B subunit expression both in vitro and in vivo. Sevoflurane-induced neuronal apoptosis was attenuated by synaptic NMDA receptors activation or low dose of exogenous NMDA in vitro. Interestingly, these effects could be abolished by NR2A inhibitor PEAQX, but not NR2B inhibitor Ifenprodil in vitro. In contrast, activation of extra-synaptic NMDA receptors alone had no effects on sevoflurane neurotoxicity. In the scenario of extra-synaptic NMDA receptors stimulation, however, sevoflurane-induced neuronal apoptosis could be prevented by addition of Ifenprodil, but not by PEAQX in vitro. In addition, sevoflurane neurotoxicity could also be rescued by memantine, an uncompetitive antagonist for preferential blockade of extra-synaptic NMDA receptors both in vitro and in vivo. Furthermore, we found that developmental sevoflurane-induced phospho-ERK1/2 inhibition was restored by synaptic NMDA receptor activation (in vitro), low dose of NMDA (in vitro) or memantine (in vivo). And the neuroprotective role of synaptic NMDA activity was able to be reversed by MEK1/2 inhibitor U0126 in vitro. Finally, administration of memantine or NMDA significantly improved spatial learning and memory dysfunctions induced by developmental sevoflurane exposure without influence on locomotor activity. These results indicated that activation of synaptic NR2A-containing NMDA receptors, or inhibition of extra-synaptic NR2B-containing NMDA receptors contributed to the relief of sevoflurane neurotoxicity, and the ERK1/2 MAPK signaling may be involved in this process.

Muscarinic M1 receptors regulate propofol modulation of GABAergic transmission in rat ventrolateral preoptic neurons.

GABAergic neurons within the ventrolateral preoptic area (VLPO) play an important role in sleep-wakefulness regulation. Propofol, a widely used systemic anesthetic, has lately been reported to excite noradrenaline (NA)-inhibited type of VLPO neurons. Present study tested if acetylcholine system takes part in the propofol modulation of GABAergic spontaneous miniature inhibitory postsynaptic currents (mIPSCs) in mechanically dissociated rat VLPO neurons using a conventional whole-cell patch clamp technique. Propofol reversibly decreased mIPSC frequency without affecting the current amplitude, indicating that propofol acts presynaptically to decrease the probability of spontaneous GABA release. The propofol action on GABAergic mIPSC frequency was completely blocked by atropine, a nonselective muscarinic acetylcholine (mACh) receptor antagonist, and pirenzepine, a selective M1 receptor antagonist. These results suggest that propofol acts on M1 receptors on GABAergic nerve terminals projecting to VLPO neurons to inhibit spontaneous GABA release. The M1 receptor-mediated modulation of GABAergic transmission onto VLPO neurons may contribute to the regulation of loss of consciousness induced by propofol.

Effects of sevoflurane and halothane anesthesia on liver circulation and oxygen metabolism in the dog during hepatolobectomy.

PURPOSE: Effects of sevoflurane and halothane anesthesia on liver circulation and oxygen metabolism during hepatolobectomy were investigated in the dog, with the aim of choosing a better anesthetic for hepatic resection. METHODS: Sixteen mongrel dogs were randomly divided into two groups with eight in each. Electromagnetic flowmeters were used to measure hepatic arterial and portal venous blood flows (1) before the inhalation of each anesthetic (base line); (2) 1 h after the start of inhalation of 1.5 minimum alveolar concentration (MAC) anesthetic; (3) 1 h after hepatolobectomy with the same MAC of anesthesia; and (4) 2 h after the discontinuation of anesthesia. Measurements of systemic hemodynamics, blood gas tensions, plasma enzyme leaks and arterial ketone body ratio were made at the same time. RESULTS: Sevoflurane maintained hepatic arterial blood flow better than halothane anesthesia, both before and after hepatolobectomy. Hepatic arterial vascular resistance increased in the halothane group but did not change in the sevoflurane group after hepatolobectomy. No significant difference was found in oxygen metabolism and arterial ketone body ratio between two groups. Serum enzyme leakage was less in the sevoflurane group. CONCLUSION: Sevoflurane has less adverse effects on liver circulation, especially hepatic arterial blood flow, and hepatic function than halothane in the case of hepatolobectomy.

[The influences of propofol on different kinds of brain injuries in rat brain slices].

OBJECTIVE: To investigate the effects of propofol on the three kinds of brain injuries induced by metabolic disorder, neurotoxicity of excitatory amino acid, and oxygen-derived free radicals in rat cerebral cortical and hippocampal slices. METHODS: Slices of rat cerebral cortex and hippocampus were made and incubated in normal artificial cerebrospinal fluid (nACSF). Then the rat cerebral cortical and hippocampal slices were divided into 2 categories: propofol group, the slices in which were co-incubated with 5, 50, or 100 micro mol/L propofol for 3 hours, and 3 experimental injury groups. Each experimental injury group was further subdivided into 3 subgroups including the slices of 4 rats. Two hours after normal incubation the slices were co-incubated with 2,3,5-triphenyltetrazolium chloride (TTC). Formazan, the red crystal product were extracted, and ELISA reader was used to read the absorbance at 490 nm (A(490)) so as to quantitatively evaluate the degree of injury. RESULTS: The values of A(490) of the slices co-incubated with propofol of different concentrations were not significantly different. Compared with those of the control subgroups, the values A490 were significantly decreased in the cerebral cortical and hippocampus slices damaged by OGD, glutamate, and H(2)O(2) injuries (all P < 0.01). The values of A(490) in the subgroups of low and middle concentrations (5 and 50 micro mol/L) of propofol plus OGD or glutamate injury were not significantly different from those of the subgroups of OGD or glutamate injury alone, both in cerebral cortical and hippocampal slices. However, the values of A(490) in the subgroups of high concentration of propofol (100 micro mol/L) plus OGD or glutamate injury was further decreased (P < 0.01). The values of A(490) in the subgroups of low and middle concentrations of propofol plus H(2)O(2) injury were significantly higher than those of the injury subgroup (all P < 0.01), however, however, the values of A490 in the high concentration propofol plus H(2)O(2) injury subgroup were significantly lower than those of the control group (all P < 0.01), even lower than that of the subgroup of H(2)O(2) injury alone. CONCLUSION: Propofol has a neuroprotective effect against hydrogen peroxide injury at low and middle concentrations. Propofol of low and middle concentrations does not improve the decrease of the value of A(490). however, propofol of high concentration augments the oxygen-glucose deprivation and glutamate injuries both in the rat cerebral cortical slices and hippocampal slices.

[The role of neuronal nicotinic acetylcholine receptors in the mechanisms of general anesthesia].

Neuronal nicotinic acetylcholine receptors (nnAChRs) are members of the ligand-gated ion channel superfamily, and widely expressed in the central and peripheral nervous systems with many subunits. NnAChRs have been represented novel targets for a wide variety of therapeutic agents based on their complex functions. It is known that both central and peripheral nnAChRs are sensitive to various types of general anesthetics, among those, barbiturates, ketamine, volatile and gaseous anesthetics depress nnAChRs at or below clinical concentrations. It is possible that inhibition of nnAChRs is one of factors involved in the mechanisms of general anesthesia.

Estrogen receptor expression in lumbar intervertebral disc of the elderly: gender- and degeneration degree-related variations.

OBJECTIVES: Sexual dimorphism does occur in intervertebral disc (IVD) degeneration. The involvement of estrogen on IVD health has been well reported in recent years. The estrogen receptors (ER) are the main mediators of estrogen action. ER might play specific roles in the sexual variations of the IVD degeneration. METHODS: Thirty-six elderly patients with lumbar disc degeneration were selected and graded using Pfirrmann's system based on MRI images. Differences of ERα and ERß immunoreactivity staining in nucleus pulposus of each sex and degeneration degree were recorded and compared. RESULTS: Both cytoplasmic and nuclear staining of ERα and ERß immunoreactivity were observed in the nucleus pulposus cells. ERα and ERß expression significantly decreased along with the aggravation of IVD degeneration both in males and females. Expression of ERα and ERß protein in nucleus pulposus of males was significantly higher than that of females. CONCLUSIONS: Gender-specific expression of ER might play a part in sexual dimorphism of IVD degeneration. Gender and degeneration condition differences should be taken into account when the effects of estrogen on IVD metabolism are studied further.

The BDNF/TrkB signaling pathway is involved in heat hyperalgesia mediated by Cdk5 in rats.

BACKGROUND: Cyclin-dependent kinase 5 (Cdk5) has been shown to play an important role in mediating inflammation-induced heat hyperalgesia. However, the underlying mechanism remains unclear. The aim of this study was to determine whether roscovitine, an inhibitor of Cdk5, could reverse the heat hyperalgesia induced by peripheral injection of complete Freund's adjuvant (CFA) via the brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB) signaling pathway in the dorsal horn of the spinal cord in rats. RESULTS: Heat hyperalgesia induced by peripheral injection of CFA was significantly reversed by roscovitine, TrkB-IgG, and the TrkB inhibitor K252a, respectively. Furthermore, BDNF was significantly increased from 0.5 h to 24 h after CFA injection in the spinal cord dorsal horn. Intrathecal adminstration of the Cdk5 inhibitor roscovitine had no obvious effects on BDNF levels. Increased TrkB protein level was significantly reversed by roscovitine between 0.5 h and 6 h after CFA injection. Cdk5 and TrkB co-immunoprecipitation results suggested Cdk5 mediates the heat hyperalgesia induced by CFA injection by binding with TrkB, and the binding between Cdk5 and TrkB was markedly blocked by intrathecal adminstration of roscovitine. CONCLUSION: Our data suggested that the BDNF-TrkB signaling pathway was involved in CFA-induced heat hyperalgesia mediated by Cdk5. Roscovitine reversed the heat hyperalgesia induced by peripheral injection of CFA by blocking BDNF/TrkB signaling pathway, suggesting that severing the close crosstalk between Cdk5 and the BDNF/TrkB signaling cascade may present a potential target for anti-inflammatory pain.

The E3 ligase APC/C-Cdh1 regulates MEF2A-dependent transcription by targeting SUMO-specific protease 2 for ubiquitination and degradation.

Activity-dependent stimuli induced a calcineurin-mediated dephosphorylation of the transcriptional factor MEF2A at serine408 and promoted a switch from SUMOylation to acetylation at lysine403 which led to MEF2A transcriptional activation. We previously identified SENP2 is the de-SUMOylation enzyme for MEF2A and promotes MEF2A-dependent transcription. We report here a requirement for APC(Cdh1)-SENP2-MEF2A axis in the regulation of MEF2A transcriptional activation. APC(Cdh1) interacts with and targets SENP2 for ubiquitination and destruction in the cytoplasm by recognizing a conserved canonical D-box motif in SENP2. Moreover, Cdh1 regulates the transcriptional activity of MEF2A in a SENP2 dependent manner. Activity-dependent stimuli prevented APC(Cdh1)-induced SENP2 ubiquitination, promoted SENP2 nuclear accumulations, and caused MEF2A de-SUMOylation and MEF2A acetylation, leading to MEF2A transcriptional activation. Thus, our findings defined a post-transcriptional mechanism underlying activity-dependent stimuli-induced MEF2A transcriptional activation.