The study of the relationship between aberrant expression of hot shock protein 70 (HSP70) and spontaneous abortion.

OBJECTIVE: The present study is aimed to explore the relationship between aberrant expression of heat shock protein 70 (HSP) and spontaneous abortion. PATIENTS AND METHODS: 50 patients with spontaneous abortion and 50 patients with induced abortion were continuously selected based on the nearest matching principle, and the proportion of age and gestational age was 1:1. The decidual tissues were obtained, and the cell apoptosis was determined by TUNEL assay. Further, the expression of HSP70 was assayed by immune-histochemical staining, and the expression of HSP70 mRNA was detected by the RT-PCR approach. RESULTS: Apoptosis rate, HSP70 expression and HSP70 mRNA expression in the observation group were significantly higher than the control group. CONCLUSIONS: HSP70 might induce apoptosis so as to cause spontaneous abortion.

Pharmacokinetics, bioavailability and PK/PD relationship of cefquinome for Escherichia coli in Beagle dogs.

The pharmacokinetics and bioavailability of cefquinome in Beagle dogs were determined by intravenous (IV), intramuscular (IM) or subcutaneous (SC) injection at a single dose of 2 mg/kg body weight (BW). The minimum inhibitory concentrations (MIC) of cefquinome against 217 Escherichia coli isolated from dogs were also investigated. After IV injection, the plasma concentration-time curve of cefquinome was analyzed using a two-compartmental model, and the mean values of t1/2α (h), t1/2ß (h), Vss (L/kg), ClB (L/kg/h) and AUC (µg·h/mL) were 0.12, 0.98, 0.30, 0.24 and 8.51, respectively. After IM and SC administration, the PK data were best described by a one-compartmental model with first-order absorption. The mean values of t1/2Kel , t1/2Ka , tmax (h), Cmax (µg/mL) and AUC (µg·h/mL) were corresponding 0.85, 0.14, 0.43, 4.83 and 8.24 for IM administration, 0.99, 0.29, 0.72, 3.88 and 9.13 for SC injection. The duration of time that drug levels exceed the MIC (%T > MIC) were calculated using the determined MIC90 (0.125 µg/mL) and the PK data obtained in this study. The results indicated that the dosage regimen of cefquinome at 2 mg/kg BW with 12-h intervals could achieve %T > MIC above 50% that generally produced a satisfactory bactericidal effect against E. coli isolated from dogs in this study.

Reduced GABA(A) receptor α6 expression in the trigeminal ganglion alters inflammatory TMJ hypersensitivity.

Trigeminal ganglia neurons express the GABA(A) receptor subunit alpha 6 (Gabrα6) but the role of this particular subunit in orofacial hypersensitivity is unknown. In this report the function of Gabrα6 was tested by reducing its expression in the trigeminal ganglia and measuring the effect of this reduction on inflammatory temporomandibular joint (TMJ) hypersensitivity. Gabrα6 expression was reduced by infusing the trigeminal ganglia of male Sprague Dawley rats with small interfering RNA (siRNA) having homology to either the Gabrα6 gene (Gabrα6 siRNA) or no known gene (control siRNA). Sixty hours after siRNA infusion the rats received a bilateral TMJ injection of complete Freund's adjuvant to induce an inflammatory response. Hypersensitivity was then quantitated by measuring meal duration, which lengthens when hypersensitivity increases. Neuronal activity in the trigeminal ganglia was also measured by quantitating the amount of phosphorylated ERK. Rats in a different group that did not have TMJ inflammation had an electrode placed in the spinal cord at the level of C1 sixty hours after siRNA infusion to record extracellular electrical activity of neurons that responded to TMJ stimulation. Our results show that Gabrα6 was expressed in both neurons and satellite glia of the trigeminal ganglia and that Gabrα6 positive neurons within the trigeminal ganglia have afferents in the TMJ. Gabrα6 siRNA infusion reduced Gabrα6 gene expression by 30% and significantly lengthened meal duration in rats with TMJ inflammation. Gabrα6 siRNA infusion also significantly increased p-ERK expression in the trigeminal ganglia of rats with TMJ inflammation and increased electrical activity in the spinal cord of rats without TMJ inflammation. These results suggest that maintaining Gabrα6 expression was necessary to inhibit primary sensory afferents in the trigeminal pathway and reduce inflammatory orofacial nociception.

Resistin level is positively correlated with thrombotic complications in Southern Chinese metabolic syndrome patients.

BACKGROUND: The metabolic syndrome (MetS) has been found to be closely related with thrombotic diseases. The mechanism, however, is far from elucidated. AIM: This study was designed to investigate the relationship between endogenous resistin and thrombosis mediating factors, as well as its potential effects on the gene expression of cardiovascular disease biomarkers. METHODS: Ninety patients satisfied the MetS criteria, and 55 healthy subjects were recruited as part of a single-center clinical study. Plasma levels of resistin, tissue factor (TF), tissue factor pathway inhibitor (TFPI), tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1) were measured by enzymelinked immunosorbent assays. The effect of resistin on the expression of cardiovascular disease biomarkers in human umbilical vein endothelial cells (HUVEC) was assayed by gene microarray. RESULTS: 1) The average levels of resistin in MetS patients with or without acute myocardial or cerebral infarction were significantly higher than those of the controls. 2) The TF and TFPI increase was higher in MetS with infarction patients than in MetS patients. 3) In MetS with infarction patients, resistin was positively correlated with TF and PAI-1 (r=0.313, p=0.008; r=0.401, p=0.002, respectively). 4) In HUVEC, the microarray showed that apolipoprotein C-I, ACE, tumor necrosis factor receptor superfamily member 1A (TNFRSF1A) and member 5 (CD40) genes expression were dramatically increased by resistin. CONCLUSION: In patients with MetS, resistin is strongly associated with hypercoagulative and hypofibrinolitic activities. Moreover, resistin may induce thrombotic complications via mediating the lipoprotein metabolism and stimulating inflammation.

Mapping and expression analyses during porcine foetal muscle development of 12 genes involved in histone modifications.

Histone modifications (methylation and demethylation) regulate gene expression and play a role in cell proliferation and differentiation by their actions on chromatin structure. In this context, we studied the temporal expression profiles of genes acting on histone methylation and demethylation during skeletal muscle proliferation and differentiation. Quantitative real-time PCR was used to quantify the mRNA levels of CARM1, JARID1A, JMJD2A, LSD1, PRMT2, PRMT5, SMYD1, SMYD2, SMYD3, SETDB1, Suv39h2 and SUZ12 in foetal skeletal muscle. Our results showed that CARM1, JARID1A, JMJD2A, SMYD1 and SMYD2 were differentially expressed in embryonic muscles of 33 days post-conception (dpc), 65 dpc and 90 dpc. These 12 genes were mapped to porcine chromosomes (SSC) 2q21-24, 5q25, 6q35, 6q12-21, 6p15, 7q21, 3q21-27, 9q26, 10p16, 4q15-16, 10q14-16 and 12p12 respectively. Taking into account the reported QTL mapping results, gene expression analysis and radiation hybrid mapping results, these results suggest that five genes (CARM1, JARID1A, JMJD2A, SMYD1 and SMYD2) could be good candidate genes for growth and backfat thickness traits.

Molecular characterization and expression pattern of the porcine STARS, a striated muscle-specific expressed gene.

STARS (striated muscle activator of Rho signaling) promotes the nuclear localization of MRTFs and mediates SRF transcription, which provides a potential muscle-specific mechanism for linking changes in the actin cytoskeleton structure with muscle gene expression. In this study, the full-length cDNA of the porcine STARS was cloned. The open reading frame of this gene contains 1,155 bp and encodes a protein of 384 amino acids, which is 79, 73, and 77% identical with human, mouse, and rat STARS genes, respectively. RT-PCR revealed that STARS is specifically expressed in heart and skeletal muscles. STARS is also distinctly different in different muscle developmental stages. The result indicates that its expression increased gradually from 33 dpc (days postcoitum) to postnatal muscles, and peaked 28 days postnatal. The porcine STARS was mapped to SSC4p13 using the somatic cell hybrid panel and the radiation hybrid panel IMpRH (LOD score 11.98). The data show that STARS is closely linked to marker SW871. A T/G single nucleotide polymorphism in the coding sequence, detected as Bsh1236I PCR-RFLP, displays allele frequency differences in six pig breeds.

Abscisic acid-specific binding sites in the flesh of developing apple fruit.

Abscisic acid (ABA) specific-binding sites localized in the cytosol were identified and characterized in the flesh of developing apple (Malus pumila L. cv. Starkrimon) fruit. ABA binding activity was scarcely detectable in the microsomes but high ABA binding activity in the cytosolic fraction was detected. The ABA-binding sites possessed a protein nature with both active serine residues and thiol-groups of cysteine residues in their functional binding sites. ABA binding was shown to be saturable, reversible and of high affinity. A Scatchard plot provided evidence for two different ABA binding proteins, one with higher affinity (K(d)=2.3 nM) and the other with lower affinity (K(d)=58.8 nM). Phaseic acid, trans-ABA and (-)-ABA had essentially no affinity for the binding proteins, indicating their stereo-specificity to bind physiologically active cis-(+)-ABA. The time-course, pH- and temperature-dependence of the ABA-binding proteins were determined. It is hypothesized that the detected ABA-binding proteins may be putative ABA-receptors that mediate ABA signals during fruit development.

GABA(A) and 5-HT(3) receptors are involved in dorsal root reflexes: possible role in periaqueductal gray descending inhibition.

The dorsal root reflex (DRR) is a measure of the central excitability of presynaptic inhibitory circuits in the spinal cord. Activation of the periaqueductal gray (PAG), a center for descending inhibition of spinal cord nociceptive transmission, induces release of variety of neurotransmitters in the spinal cord, including GABA and serotonin (5-HT). GABA has been shown to be involved in generation of DRRs. In this study, pharmacological agents that influence DRRs and their possible mechanisms were investigated. DRRs were recorded in anesthetized rats from filaments teased from the cut central stump of the left L(4) or L(5) dorsal root, using a monopolar recording electrode. Stimulating electrodes were placed either on the left sciatic nerve or transcutaneously in the left foot. Animals were paralyzed and maintained by artificial ventilation. Drugs were applied topically to the spinal cord. A total of 64 units were recorded in 34 Sprague-Dawley rats. Peripheral receptive fields were found for nine of these units. In these units, DRRs were evoked by brush, pressure, and pinch stimuli. Nine units were tested for an effect of electrical stimulation in the periaqueductal gray on the DRRs. In eight cases, DRR responses were enhanced following PAG stimulation. The background activity was 4.2 +/- 1.9 spikes/s (mean +/- SE; range: 0-97.7; n = 57). The responses to agents applied to the spinal cord were (in spikes/s): artificial cerebrospinal fluid, 7.1 +/- 3.6 (range: 0-86.9; n = 25); 0.1 mM GABA, 16.8 +/- 8.7 (range: 0-191.0; n = 22); 1.0 mM GABA, 116.0 +/- 26.5 (range: 0.05-1001.2; n = 50); and 1.0 mM phenylbiguanide (PBG), 68.1 +/- 25.3 (range: 0-1,073.0; n = 49). Bicuculline (0.5 mM, n = 27) and ondansetron (1.0 mM, n = 10) blocked the GABA and PBG effects, respectively (P < 0.05). Significant cross blockade was also observed. It is concluded that GABA(A) receptors are likely to play a key role in the generation of DRRs, but that 5-HT(3) receptors may also contribute. DRRs can be modulated by supraspinal mechanisms through descending systems.

Capsaicin responses in heat-sensitive and heat-insensitive A-fiber nociceptors.

The recently cloned vanilloid receptor (VR1) is postulated to account for heat and capsaicin sensitivity in unmyelinated afferents. We sought to determine whether heat and capsaicin sensitivity also coexist in myelinated nociceptive afferents. Action potential (AP) activity was recorded from single A-fiber nociceptors that innervated the hairy skin in monkey. Before intradermal injection of capsaicin (10 microg/10 microl) into the receptive field, nociceptors were classified as heat-sensitive (threshold,

Altered nociceptive neuronal circuits after neonatal peripheral inflammation.

Nociceptive neuronal circuits are formed during embryonic and postnatal times when painful stimuli are normally absent or limited. Today, medical procedures for neonates with health risks can involve tissue injury and pain for which the long-term effects are unknown. To investigate the impact of neonatal tissue injury and pain on development of nociceptive neuronal circuitry, we used an animal model of persistent hind paw peripheral inflammation. We found that, as adults, these animals exhibited spinal neuronal circuits with increased input and segmental changes in nociceptive primary afferent axons and altered responses to sensory stimulation.

Electrophysiological assessment of the cutaneous arborization of Adelta-fiber nociceptors.

Little is known about the relationship between the branching structure and function of physiologically identified cutaneous nociceptor terminals. The axonal arborization itself, however, has an impact on the afferent signal that is conveyed along the parent axon to the CNS. We therefore developed electrophysiological techniques to investigate the branching structure of cutaneous nociceptors. Single-fiber recordings were obtained from physiologically identified nociceptors that innervated the hairy skin of the monkey. Electrodes for transcutaneous stimulation were fixed at two separate locations inside the receptive field. For 32 Adelta-fiber nociceptors, distinct steps in latency of the recorded action potential were observed as the intensity of the transcutaneous electrical stimulus increased, indicating discrete sites for action potential initiation. The number of discrete latencies at each stimulation location ranged from 1 to 9 (3.7 +/- 0. 2; mean +/- SE) and the mean size of the latency step was 9.9 +/- 1. 0 ms (range: 0.4-89.1 ms). For seven Adelta fibers, collision techniques were used to locate the position of the branch point where the daughter fibers that innervated the two locations within the receptive field join the parent axon. To correct for changes in electrical excitability at the peripheral terminals, collision experiments between the two skin locations and between each skin location and a nerve trunk electrode were necessary. Nine branch points were studied in the seven Adelta fibers; the mean propagation time from the action potential initiation site to the branch point was 31 +/- 5 ms corresponding to a distance of 54 +/- 10 mm. Almost half of the daughter branches were unmyelinated. These results demonstrate that collision techniques can be used to study the functional anatomy of physiologically identified nociceptive afferent terminals. Furthermore these results indicate that some nociceptive afferents branch quite proximal to their peripheral receptive field. Occlusion of action potential activity can occur in these long branches such that the shorter branches dominate in the response to natural stimuli.

Nitric oxide mediates the central sensitization of primate spinothalamic tract neurons.

Nitric oxide (NO) has been proposed to contribute to the development of hyperalgesia by activating the NO/guanosine 3',5'-cyclic monophosphate (cGMP) signal transduction pathway in the spinal cord. We have examined the effects of NO on the responses of primate spinothalamic tract (STT) neurons to peripheral cutaneous stimuli and on the sensitization of STT cells following intradermal injection of capsaicin. The NO level within the spinal dorsal horn was increased by microdialysis of a NO donor, 3-morpholinosydnonimine (SIN-1). SIN-1 enhanced the responses of STT cells to both weak and strong mechanical stimulation of the skin. This effect was preferentially on deep wide dynamic range STT neurons. The responses of none of the neurons tested to noxious heat stimuli were significantly changed when SIN-1 was administered. Intradermal injection of capsaicin increased dramatically the content of NO metabolites, NO-2/NO-3, within the dorsal horn. This effect was attenuated by pretreatment of the spinal cord with a nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). Sensitization of STT cells induced by intradermal injection of capsaicin was also prevented by pretreatment of the dorsal horn with the NOS inhibitors, L-NAME or 7-nitroindazole. Blockade of NOS did not significantly affect the responses of STT cells to peripheral stimulation in the absence of capsaicin injection. The data suggest that NO contributes to the development and maintenance of central sensitization of STT cells and the resultant mechanical hyperalgesia and allodynia after peripheral tissue damage or inflammation. NO seems to play little role in signaling peripheral stimuli under physiological conditions.

Nitric oxide-mediated spinal disinhibition contributes to the sensitization of primate spinothalamic tract neurons.

This study concentrated on whether an increase in spinal nitric oxide (NO) diminishes inhibition of spinothalamic tract (STT) cells induced by activating the periaqueductal gray (PAG) or spinal glycinergic and GABAergic receptors, thus contributing to the sensitization of STT neurons. A reduction in inhibition of the responses to cutaneous mechanical stimuli induced by PAG stimulation was seen in wide dynamic range (WDR) STT cells located in the deep layers of the dorsal horn when these neurons were sensitized during administration of a NO donor, 3-morpholinosydnonimine (SIN-1), into the dorsal horn by microdialysis. In contrast, PAG-induced inhibition of the responses of high-threshold (HT) and superficial WDR STT cells was not significantly changed by spinal infusion of SIN-1. A reduction in PAG inhibition when STT cells were sensitized after intradermal injection of capsaicin could be nearly completely blocked by pretreatment of the dorsal horn with a NO synthase inhibitor, 7-nitroindazole. Moreover, spinal inhibition of nociceptive activity of deep WDR STT neurons elicited by iontophoretic release of glycine and GABA agonists was attenuated by administration of SIN-1. This change paralleled the change in PAG-induced inhibition. However, the inhibition of HT and superficial WDR cells induced by glycine and GABA release did not show a significant change when SIN-1 was administered spinally. Combined with our recent results, these data show that the effectiveness of spinal inhibition can be reduced by the NO/cGMP pathway. Thus disinhibition may constitute one mechanism underlying central sensitization.

Inhibition of primate spinothalamic tract neurons by spinal glycine and GABA is modulated by guanosine 3',5'-cyclic monophosphate.

Our recent work has suggested that the nitric oxide/guanosine 3', 5'-cyclic monophosphate (NO/cGMP) signal transduction system contributes to central sensitization of spinothalamic tract (STT) neurons in part by influencing the descending inhibition of nociception resulting from stimulation in the periaqueductal gray. This study was designed to examine further whether activation of the NO/cGMP cascade reduces the inhibition of the activity of STT neurons mediated by spinal inhibitory amino acid (IAA) receptors. Responses of STT cells to noxious cutaneous stimuli were inhibited by iontophoresis of glycine and GABA agonists in anesthetized monkeys. Administration of 8-bromoguanosine-3',5'-cyclophosphate sodium (8-bromo-cGMP), a membrane permeable analogue of cGMP, either by microdialysis or by iontophoresis reduced significantly the IAA-induced inhibition of wide dynamic range (WDR) STT cells in the deep layers of the dorsal horn. The reduction in inhibition lasted for up to 1-1.5 h after the cessation of drug infusion. In contrast, IAA-induced inhibition of WDR STT cells in the superficial dorsal horn and high-threshold (HT) cells in superficial or deep layers was not significantly changed during 8-bromo-cGMP infusion. Iontophoresis of 8-bromo-cGMP onto STT cells produced the same actions as produced by microdialysis of this agent, but the effect was not as long-lasting nor as potent. Finally, an attenuation of the IAA receptor-mediated inhibition of STT cells produced by iontophoretic release of a NO donor, 3-morpholinosydnonimine, could be blocked by pretreatment of the spinal cord with a guanylate cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. These results suggest that an increased spinal cGMP level contributes to the sensitization of WDR STT neurons in the deep dorsal horn in part by down-regulating spinal IAA receptors. However, no evidence is provided in this study that the NO/cGMP cascade regulates IAA receptors on HT and superficial WDR neurons. Combined with the preceding studies, our data support the view that NO and cGMP function in the same signal transduction cascade and play an important role in central sensitization.

Polycaprolactone/glass bioabsorbable implant in a rabbit humerus fracture model.

Research in improved materials and methods for internal fixation has centered on internal fixators made of bioabsorbable materials such as polylactic acid, polyglycolic acid, and polyparadioxanone. These materials have two problems: the first is a postoperative complication related to a delayed inflammatory response; and the second is low strength characteristics. An alternative material developed to alleviate these problems is a composite of phosphate glass fibers embedded in the polymer polycaprolactone, referred to as PCL. In this study, intramedullary pins made of PCL were compared to stainless steel pins in a rabbit humerus osteotomy model. Specimens were harvested at 0, 6, and 12 weeks postoperatively, radiographs and mechanical testing to failure were performed at each time interval, and tissue was examined microscopically at 6 and 12 weeks. Histologic results showed PCL pins to be well tolerated with minimal inflammation around the pin. Mechanical testing revealed the PCL fixation to be weaker initially than the stainless steel fixation. There was significant stress shielding of stainless-steel-healed rabbit humeri when compared to the PCL/bone humeri. All osteotomies immobilized with PCL healed with abundant periosteal callus production.

Involvement of protein kinase C in responses of rat dorsal horn neurons to mechanical stimuli and periaqueductal gray descending inhibition.

The effects of a protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), on the activity and periaqueductal gray (PAG)-induced inhibition of rat dorsal horn neurons of the lumbar spinal cord were tested. A microdialysis fiber was placed through the dorsal horn for the purpose of local application of pharmacological agents. Extracellular single-unit recordings from dorsal horn neurons were made near the microdialysis fiber. TPA was tested on nociceptive dorsal horn cells. There was a significant increase in the background activity and responses to "brush", with no changes in responses to pressure and pinch stimuli. TPA also significantly blocked the PAG-induced inhibition of responses to brush, press, and pinch. These effects were eliminated by coadministration of the PKC inhibitor NPC-15437. The solvent, which contained dimethyl sulfoxide, was also tested for its effect on the responses to peripheral mechanical stimuli and PAG-induced inhibition of the dorsal horn neurons. There were no significant changes. This experiment suggests that activation of the PKC second messenger system might increase the activity of dorsal horn neurons and their responses to peripheral stimuli; in addition, the phorbol ester attenuated the PAG-induced descending inhibition of the dorsal horn neuron activity.

Involvement of cGMP in nociceptive processing by and sensitization of spinothalamic neurons in primates.

Central sensitization of spinothalamic tract (STT) neurons in anesthetized monkeys after intradermal injection of capsaicin depends in part on disinhibition. Protein kinase C is suggested to participate in this process. The present study shows that the nitric oxide-cGMP (NO-cGMP) signal transduction system also contributes to sensitization of wide dynamic range (WDR) STT neurons located in the deep dorsal horn. The NO-cGMP system was activated by microdialysis administration into the dorsal horn of 8-bromo-cGMP, an analog of cGMP. Sensitization of STT cells by 8-bromo-cGMP increased the responses of deep WDR STT cells to both weak and strong mechanical stimulation of the skin and simultaneously attenuated the inhibition of the same neurons produced by stimulation in the periaqueductal gray (PAG). In contrast, WDR STT cells in the superficial dorsal horn and high-threshold (HT) STT cells in superficial or deep layers showed reduced responses to mechanical stimulation of the skin after infusion of 8-bromo-cGMP, and PAG inhibition of these neurons was unaffected. Sensitization of STT cells and the attenuation of PAG inhibition induced by intradermal injection of capsaicin were prevented by preteatment of the dorsal horn with a guanylate cyclase inhibitor, 1 H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. The results support the hypothesis that activation of the NO-cGMP signal transduction system contributes to the sensitization of WDR STT neurons in the deep dorsal horn and helps explain why intradermal capsaicin injections often fail to sensitize superficial and HT STT cells. The results also support the idea that sensitization of STT cells is produced in part by disinhibition.

Effects of GABA and glycine receptor antagonists on the activity and PAG-induced inhibition of rat dorsal horn neurons.

The effects of bicuculline and strychnine on the activity and periaqueductal gray (PAG)-induced inhibition of rat dorsal horn neurons of the lumbar spinal cord were tested. Extracellular single unit recordings were from 36 dorsal horn neurons near a microdialysis fiber passed through the spinal cord for drug application. The GABAA receptor antagonist, bicuculline, was tested on 19 cells, whereas the glycine receptor antagonist, strychnine, was tested on 17 cells. Both bicuculline and strychnine increased the background activity and responses to mechanical stimulation (BRUSH, PRESS, and PINCH) of the skin.06 They also significantly blocked the PAG-induced inhibition of responses to peripheral mechanical stimuli. This experiment suggests that the mechanism of PAG-induced descending inhibition of dorsal horn neuron activity involves GABA and/or glycine release in the spinal cord and that there is tonic release of these inhibitory neurotransmitters.

Inhibition of primate spinothalamic tract neurons by spinal glycine and GABA is reduced during central sensitization.

1. In our previous work, we demonstrated that the glycinergic and GABAergic mechanisms that help mediate the descending inhibition from the periaqueductal gray exert a tonic modulation of nociceptive inputs through spinal glycine and gamma-aminobutyric acid (GABA) receptors. This study was designed to examine further possible changes in the inhibition of the activity of spinothalamic tract (STT) neurons mediated by spinal glycine and GABA receptors when STT cells are sensitized by intradermal injection of capsaicin, and to investigate the role of the protein kinase C (PKC) system in the functional modulation of these receptors. 2. Although the responses of STT cells to cutaneous mechanical stimuli were sensitized by intradermal injection of capsaicin, the inhibition of the responses of all STT cells tested to noxious cutaneous stimuli produced by iontophoretic release of glycine and GABA was significantly attenuated. The inhibition elicited by iontophoretic application of a GABAA agonist, muscimol, was reduced in some of the cells tested. 3. When the spinal cord dorsal horn was pretreated with a selective PKC inhibitor, 2,6-diamino-N-([1-oxotridecyl-2-piperidinyl]- methyl)hexanamide, by microdialysis, sensitization of STT cells by capsaicin injection and the accompanying attenuation of glycine- and GABA-induced inhibition were prevented. 4. Sensitization of STT cells to cutaneous mechanical stimuli was also induced by administration of the PKC activator, 12-O-tetradecanoylphorbol-13-acetate, into the spinal dorsal horn. The inhibition produced by iontophoretic release of glycine, GABA, and muscimol was found to be reduced in most cells examined when this phorbol ester was used. An inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate, did not produce significant effects on cellular activity. 5. These results suggest that there is an activation of PKC in the spinal cord when STT neurons are sensitized after intradermal injection of capsaicin or administration of phorbol ester. This sensitization is likely to be involved in the development of allodynia and secondary hyperalgesia not only by enhancing the responses of excitatory amino acid receptors but also by desensitizing glycine and GABA receptors.