Serum proteomic analysis of a pre-symptomatic multiple sclerosis cohort.

BACKGROUND AND PURPOSE: Susceptibility to multiple sclerosis (MS) is determined by environmental and genetic factors, but the cause remains unknown. Changes to the proteome prior to first symptom onset may reflect the underlying pathophysiology of the disease. METHODS: This preliminary study utilized pre-symptomatic and post-symptomatic serum from a sample of 100 incident population-based US military veterans with MS along with 100 matched healthy controls. All samples were obtained from the Department of Defense Serum Repository. Multidimensional protein identification technology tandem mass spectrometry analysis was performed on tryptic peptides of lectin-captured glycosylated serum proteins following albumin/immunoglobulin G depletion. Identified proteins were analyzed with the Ingenuity Pathway Analysis program. RESULTS: The mean intervals between first symptom onset and the collection of pre-symptomatic and post-symptomatic sera were -6.0 and +1.1 years, respectively. Pre-symptomatic proteins from the MS group were differentially regulated compared with both control groups indicating that proteomic changes are detected prior to symptom onset. Pathway analysis showed that proteins involved in the complement and coagulation pathways and lipid transport are significantly altered in the serum of subjects with MS compared with healthy donors. CONCLUSIONS: Compared with healthy controls, differential proteomic changes were noted in the serum of patients with MS that preceded the onset of symptomatic disease. Further work is in progress to confirm or refute these findings.

Impaired long-term memory and long-term potentiation in N-type Ca2+ channel-deficient mice.

Voltage-dependent N-type Ca(2+) channels, along with the P/Q-type, have a crucial role in controlling the release of neurotransmitters or neuromodulators at presynaptic terminals. However, their role in hippocampus-dependent learning and memory has never been examined. Here, we investigated hippocampus-dependent learning and memory and synaptic plasticity at hippocampal CA3-CA1 synapses in mice deficient for the alpha(1B) subunit of N-type Ca(2+) channels. The mutant mice exhibited impaired learning and memory in the Morris water maze and the social transmission of food preference tasks. In particular, long-term memory was impaired in the mutant mice. Interestingly, among activity-dependent long-lasting synaptic changes, theta burst- or 200-Hz-stimulation-induced long-term potentiation (LTP) was decreased in the mutant, compared with the wild-type mice. This type of LTP is known to require brain-derived neurotrophic factor (BDNF). It was found that both BDNF-induced potentiation of field excitatory postsynaptic potentials and facilitation of the frequency of miniature excitatory postsynaptic currents (mEPSCs) were reduced in the mutant. Taken together, these results demonstrate that N-type Ca(2+) channels are required for hippocampus-dependent learning and memory, and certain forms of LTP.

Intracellular ATP increases capsaicin-activated channel activity by interacting with nucleotide-binding domains.

Capsaicin (CAP)-activated ion channel plays a key role in generating nociceptive neural signals in sensory neurons. Here we present evidence that intracellular ATP upregulates the activity of capsaicin receptor channel. In inside-out membrane patches isolated from sensory neurons, application of CAP activated a nonselective cation channel (i(cap)). Further addition of ATP to the bath caused a significant increase in i(cap), with a K(1/2) of 3.3 mm. Nonhydrolyzable analogs of ATP, adenylimidodiphosphate and adenosine 5'-O-(3-thio)-triphosphate, also increased i(cap). Neither Mg(2+)-free medium nor inhibitors of various kinases blocked the increase in i(cap) induced by ATP. The enhancing effect of ATP was also observed in inside-out patches of oocytes expressing vanilloid receptor 1, a cloned capsaicin receptor. Single point mutations (D178N, K735R) within the putative Walker type nucleotide-binding domains abolished the effect of ATP. These results show that ATP increases i(cap) in sensory neurons by direct interaction with the CAP channel without involvement of phosphorylation.

Chronic effects of topical application of capsaicin to the sciatic nerve on responses of primate spinothalamic neurons.

The responses of 144 spinothalamic tract (STT) cells were recorded in 15 anesthetized macaque monkeys (Macaca fascicularis). Three to 4 weeks prior to the acute experiment, the sciatic nerve was surgically exposed on one or both sides so that capsaicin or vehicle could be applied. Responses of STT cells recorded in 3 experimental groups were compared: untreated (21 cells), vehicle-treated (40 cells), and capsaicin-treated (83 cells). The background activity of cells in the vehicle- and capsaicin-treated groups was the same as in the untreated group (that is, cells on the side contralateral to surgery). Responses to innocuous (BRUSH) and noxious (PINCH) mechanical stimuli were unchanged by vehicle or by capsaicin treatment. However, responses to other noxious (PRESSURE and SQUEEZE) mechanical stimuli were significantly increased in the vehicle-treated group. Compared with a large reference population, all experimental groups showed a significant increase in overall responsiveness to mechanical stimuli (as determined by cluster analysis), greatest in the vehicle-treated group. Responses to noxious heat stimuli were significantly reduced in the capsaicin-treated group for 45 degrees C and 47 degrees C stimuli. Volleys in A fibers, probably A delta fibers, evoked prolonged responses in many STT cells of all treatment groups. Electron microscopic counts of axons in the sciatic nerves of animals treated with capsaicin showed a reduced number of C fibers but no appreciable loss of myelinated axons. This loss of unmyelinated sensory fibers was presumably responsible for the reduction in the responses of the STT cells to noxious heat stimuli. Increased responses to some noxious mechanical stimuli and to A fiber volleys may have been the consequence of several factors, including surgical manipulation, a chemical action of vehicle and a contralateral action of capsaicin treatment.

A capsaicin-receptor antagonist, capsazepine, reduces inflammation-induced hyperalgesic responses in the rat: evidence for an endogenous capsaicin-like substance.

In the present study, the presence of an endogenous capsaicin-like substance and the role of capsaicin receptors in nociception during inflammation were assessed using Fos immunohistochemistry and the paw-withdrawal test in rats. Intradermal injection of carrageenan in the hind-paw produced inflammation in the foot pad, increased the number of cells exhibiting Fos-like immunoreactivity in the dorsal horn of the spinal cord, and decreased the paw-withdrawal latency. Intradermal injection of capsazepine, a capsaicin-receptor antagonist, significantly reduced the number of cells exhibiting Fos-like immunoreactivity, significantly increased the paw-withdrawal latency, but did not decrease inflammation induced by carrageenan injection. Intradermal injection of capsaicin or formalin also increased Fos-positive neurons. Capsaicin- or formalin-induced Fos expression was reduced in both cases by pretreatment of capsazepine, but to a much lesser extent for formalin. The capsazepine inhibition of carrageenan inflammation-induced hyperalgesic responses strongly suggests that an endogenous capsaicin-like substance is released in inflamed tissues and produces nociceptive neural impulses by acting on capsaicin receptors present on sensory neurons. Furthermore, our results indicate that capsaicin receptors take part only in generating nociceptive signals in sensory neurons, but not in activating the inflammation-promoting cells.

Dynamic chromatin remodeling in the vicinity of J chain gene for the regulation of two stage-specific genes during B cell differentiation.

Dynamic chromatin remodeling during B cell differentiation was identified in the vicinity of J chain gene. In pre-B cells, the enhancer-containing DNase I hypersensitive sites (HSSs) 3-4 were open. However, these HSSs 3-4 turned out to be unassociated with J chain gene expression, as the J chain promoter-containing HSS1 remained in a closed state. The open enhancer HSSs 3-4 in the pre-B cells might be related to the expression of a pre-B cell-specific gene upstream of the HSSs 3-4, which was identified in our Northern blot analyses. The HSSs 3-4 are then closed in the next immature and mature B cell stages until the IL-2 opens the HSSs 3-4 again as well as HSS1 to express J chain gene in the primary immune responses. The dynamic regulation of chromatin structure during B cell differentiation for the expression of two stage-specific genes will provide a good model system for the study of B cell differentiation and gene expression.

Effects of ginsenosides on vanilloid receptor (VR1) channels expressed in Xenopus oocytes.

Ginsenosides, or ginseng saponins, are biologically active ingredients of Panax ginseng. Accumulating evidence suggests that ginsenosides can alleviate pain from injections of noxious chemicals, such as capsaicin [Nah et al. (2000)]. In this study we examined the effects of ginsenoside Rc on the capsaicin-induced inward current in Xenopus oocytes that expresses the vanilloid receptor 1 (VR1). Ginsenoside Rc enhanced the capsaicin-induced inward current in a concentration-dependent and reversible manner, but ginsenoside Rc itself elicited no membrane currents. The VR1 antagonist capsazepine almost completely blocked the inward current that was elicited by capsaicin plus ginsenoside Rc. We also tested the effect of seven other fractionated ginsenosides (i.e., Rb1, Rb2, Rd, Re, Rf, Rg1, and Rg2) in addition to ginsenoside Rc. We found that six of them significantly enhanced the inward current that is induced by capsaicin with the following order of potency: Rc > Rf > Rg1 approximately Rd > Rb2 > Rb1. These results show the possibility that the in vivo effect of ginsenosides against capsaicin-induced pain is derived from their modulation of the VR1 channel function.

Electrophysiological evidence for an increase in the number of ventral root afferent fibers after neonatal peripheral neurectomy in the rat.

Our recent study has shown that many afferent fibers in the ventral root are third branches of dorsal root ganglion cells in addition to their processes in the peripheral nerve and the dorsal root. From results of this study, we hypothesized that most of the afferent fibers in the normal ventral root are extra processes of certain dorsal root ganglion cells. To accommodate experimental findings by others, we formulated several working hypotheses in the present study as an extension of our previous hypothesis: these afferent processes in the ventral root are of varying length; they end bluntly along the length of the root; and in an event such as peripheral neurectomy in the neonatal stage, these fibers sprout at the blunt endings along the length of the ventral root. We tested the above hypotheses using electrophysiological methods. The sciatic nerve on one side in neonatal rats was cut. After the rat was fully grown, volleys of neural activity were recorded along the length of the ventral root while stimulating the dorsal root of the same segment. There was a great increase in the size of compound action potentials in the ventral root on the sciatic nerve-lesioned side. Various lines of evidence suggest that this enhancement of the evoked potentials is likely to be due to an increase in the number of afferent fibers in the ventral root in response to neonatal peripheral nerve injury. The results are consistent with our hypotheses.

The cAMP-dependent kinase pathway does not sensitize the cloned vanilloid receptor type 1 expressed in xenopus oocytes or Aplysia neurons.

Capsaicin-activated channels present in sensory neurons are ligand-gated cation channels that largely account for mediating some types of pain. The cAMP-dependent protein kinase (PKA) signal pathway was suggested to mediate the prostaglandin-induced enhancement of capsaicin-evoked inward current (I(CAP)) in rat sensory neurons. It is not clear, however, whether PKA acts directly on the capsaicin-sensitive channel that is responsible for I(CAP). To address this issue, we overexpressed the cloned capsaicin receptor, VR1, in heterologous expression systems such as Xenopus oocytes or Aplysia R2 neuron and stimulated PKA pathways. As a result, activation of PKA by applying either 8-bromo-cAMP or forskolin with 3-isobutyl-1-methylxanthine or through activation of beta(2) adrenergic receptors failed to enhance I(CAP) in oocytes or R2 neurons expressing VR1. Our results raise two possibilities. (1) Direct phosphorylation of VR1 by PKA may not be responsible for the sensitization; instead, phosphorylation of regulatory proteins associated with VR1 would account for the sensitization of I(CAP) evoked by prostaglandin E(2) in dorsal root ganglion (DRG) neurons. (2) DRG neurons may have a different PKA signaling mechanism that is not replicable in Xenopus oocytes or Aplysia R2 neurons.

Differences in sensitivity of vanilloid receptor 1 transfected to human embryonic kidney cells and capsaicin-activated channels in cultured rat dorsal root ganglion neurons to capsaicin receptor agonists.

Heterologously expressed vanilloid receptor 1 (VR1), a cloned cDNA encoding for capsaicin (CAP)-sensitive currents, resembles the native CAP channels in cultured sensory neurons in channel property. But, the pharmacological profile of VR1 to various CAP analogs is not known. The stable expression of VR1 in human embryonic kidney (HEK) cells was generated and confirmed by reverse transcription-polymerase chain reaction and Western blots. VR1 expressed in HEK cells retained single-channel properties similar to those of the native channels. When concentration-response relationships were compared, CAP and DA-5018.HCl, a synthetic analog of CAP, exhibited a greater potency in activating VR1 than the native channels in sensory neurons. In contrast, resiniferatoxin and its analog, phorbol 12-phenylacetate 13-acetate 20-homovanillate, was more potent in activating the CAP-activated channels in cultured sensory neurons than VR1. Thus, the difference in pharmacological profiles of VR1 and the native channels suggests the possible presence of subtypes of the CAP receptor or regulatory mechanisms associated with VR1.

Alternative approach: a systematic review of non-pharmacological non-spastic and non-trigeminal pain management in multiple sclerosis.

The aim of this paper was to evaluate non-pharmacological strategies for the reduction of non-spastic and non-trigeminal pain in patients with multiple sclerosis (MS) by conducting a systematic review. Experimental studies published after 1965 were chosen for review by searching electronic databases (e.g. PubMed, Cumulative Index to Nursing and Allied Health Literature, Science Citation Index Expanded, Conference Proceedings Citation Index- Science, and clinicaltrials.gov) and bibliographies/citations of previously published reviews. Studies were included if all participants were adults clinically diagnosed with MS, study sample was not restricted to participants with spasticity or trigeminal neuralgia, and participant-reported pain was a primary or secondary outcome measured with a previously validated tool. Records were screened and methodological qualities of included studies were assessed independently by two reviewers under the supervision of another reviewer. Pain scores were recorded as mean differences between or within groups weighted by the inverse of the pooled standard deviation (Cohen's d). A total of 13 studies which met the inclusion and exclusion criteria were identified for review; interventions included education, electrical stimulation, and physical therapies. Meta-analyses were not performed due to few trials identified per treatment within these classes. Pain relief was reported compared to placebo for two trials in transcutaneous electrical nerve stimulation (TENS) with effect sizes of -3.37 and -3.32, respectively. Inconclusive pain relief was reported for other education and physical therapies. TENS may be effective in reducing central neuropathic pain in MS. More trials with rigorous design and reporting are needed to determine effective treatments for specific pain types presenting in people living with MS.

A role for Piezo2 in EPAC1-dependent mechanical allodynia.

Aberrant mechanosensation has an important role in different pain states. Here we show that Epac1 (cyclic AMP sensor) potentiation of Piezo2-mediated mechanotransduction contributes to mechanical allodynia. Dorsal root ganglia Epac1 mRNA levels increase during neuropathic pain, and nerve damage-induced allodynia is reduced in Epac1-/- mice. The Epac-selective cAMP analogue 8-pCPT sensitizes mechanically evoked currents in sensory neurons. Human Piezo2 produces large mechanically gated currents that are enhanced by the activation of the cAMP-sensor Epac1 or cytosolic calcium but are unaffected by protein kinase C or protein kinase A and depend on the integrity of the cytoskeleton. In vivo, 8-pCPT induces long-lasting allodynia that is prevented by the knockdown of Epac1 and attenuated by mouse Piezo2 knockdown. Piezo2 knockdown also enhanced thresholds for light touch. Finally, 8-pCPT sensitizes responses to innocuous mechanical stimuli without changing the electrical excitability of sensory fibres. These data indicate that the Epac1-Piezo2 axis has a role in the development of mechanical allodynia during neuropathic pain.

Brain volume measurements in patients with human T-cell lymphotropic virus-1-associated tropical spastic paraparesis.

Human T-cell lymphotropic virus (HTLV)-1 is associated with a chronic progressive neurologic disease known as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) that affects 0.2% to 3% of HTLV-1-infected people. The authors aimed at exploring, in vivo, whether brain volume reduction occurs in patients with HAM/TSP through the use of magnetic resonance imaging (MRI). T1 pre/postcontrast spin echo-weighted images (WIs) and T2WIs of the brain were obtained in 19 HAM/TSP patients and 14 age-and sex-matched healthy volunteers. Both patients and healthy individuals were imaged at a 1.5-Tesla magnet by employing a conventional head coil. Focal T1 and T2 abnormalities were calculated and two measurements of brain parenchyma fraction (BPF) were obtained by using SIENAx (Structural Image Evaluation,using Normalisation, of Atrophy; University of Oxford, Oxford, UK) and MIPAV (Medical Image Processing, Analysis, and Visualization; National Institutes of Health, Bethesda, USA) from T1WIs. No significant differences in BPF were found between patients and healthy subjects when using either SIENAx or MIPAV. Analysis of individual patients detected that BPF was lower by 1 standard deviation (SD) relative to patients' average BPF in one patient. The authors conclude that reductions in BPF do not occur frequently in patients with HAM/TSP. However, the authors believe that one individual case of significant brain atrophy raises the question as to whether atrophy selectively targets the spinal cord of HAM/TSP patients or may involve the brain as well. A larger patient population analyzing regional brain volume changes could be helpful in determining whether brain atrophy is a marker of disease in patients with HAM/TSP.

Amino acid substitution within the S2 and S4 transmembrane segments in Shaker potassium channel modulates channel gating.

To investigate of the gating properties in the voltage-activated potassium channel, we have mutated a variety of S2 and S4 residues in the Shaker potassium protein. Results showed that the R365C and R368C, but not the E283C, R362C, R365S, R368S or the ShB-IR, were sensitive to micromolar concentrations of Cd(2+) ions. This indicates that R365 and R368 play a crucial role in the channel gating due to a conformational modulation of the channel structure. Doubly mutated channels of the E283C/R365E and E283C/R368E caused a transient increase in current amplitude, which reached a peak within a few seconds and then decreased toward initial levels, despite the continual presence of Cd(2+). Taken together, our results suggest that E283, R365, and R368 form a network of strong, local, and electrostatic interactions that relate closely to the mechanism of the channel gating.

Capsaicin activates a nonselective cation channel in cultured neonatal rat dorsal root ganglion neurons.

Capsaicin (CAP), a neurotoxin, has been reported to activate a nonselective cation current in dorsal root ganglion (DRG) neurons. In this paper, we identify and describe the properties of CAP-activated single channels in cultured neonatal rat DRG neurons. We first identified CAP-sensitive whole-cell currents that reversed near 0 mV in physiological solution. In solution containing 140 mM Na+, extracellular application of CAP to outside-out patches caused activation of an ion channel in a concentration-dependent manner (EC50 = 1.1 microM). The channel was blocked by the CAP antagonist capsazepine (10 microM). The channel was also activated by 2-10 nM resiniferatoxin, a potent analog of CAP. In symmetrical 140 mM Na+, the single-channel slope conductances were 45.3 +/- 1.0 and 80.0 +/- 4.2 pS at -60 and +60 mV, respectively, showing outward rectification (n = 9). The reversal potential did not shift significantly when Na+ was replaced by K+, Cs+, Rb+, or Li+, showing that the channel discriminated poorly among cations. The channel was also permeable to Ca2+. Although acid (pH < 6.2) was suggested to be an endogenous activator of the CAP receptor, an acid solution (pH 5.9-6.0) failed to activate the channels in outside-out patches. This is the first clear demonstration of the presence of the CAP-activated ion channel in DRG neuron. Opening of these ligand-gated, cation-selective channels gives rise to the whole-cell CAP-activated current in DRG neurons and may underlie the neurotoxic effects of CAP.

Different properties of the atrial G protein-gated K+ channels activated by extracellular ATP and adenosine.

Extracellular ATP (ATPo) and adenosine activate G protein-gated inwardly rectifying K+ currents in atrial cells. Earlier studies have suggested that the two agonists may use separate pathways to activate the K+ current. Therefore, we examined whether the K+ channels activated by the two agonists have different properties under identical ionic conditions. In cell-attached patches, K+ channels activated by 100 microM ATP in the pipette had a single-channel conductance and mean open time of 32.0 +/- 0.2 pS and 0.5 +/- 0.1 ms, respectively, compared with 31.3 +/- 0.3 pS and 0.9 +/- 0.1 ms for the K+ channels activated by adenosine (140 mM KCl). With ATPo as the agonist, the K+ channel activity in cell-attached patches was approximately threefold lower than that in inside-out patches with 100 microM GTP in the bath. Applying ATP to the cytoplasmic side of the membrane (ATPi) produced a biphasic concentration-dependent effect on channel activity: an increase at low [mean affinity constant (K0.5) = 190 microM] and a decrease at high (K0.5 = 1.3 mM) concentrations. In contrast, with adenosine as the agonist, K+ channel activity in cell-attached patches was approximately fourfold greater than that in inside-out patches with 100 microM GTP in the bath. In inside-out patches, ATPi only augmented the K+ channel activity (K0.5 = 32 microM). These results show that although both ATPo and adenosine activate kinetically similar K+ channels in atrial cells, the channels are regulated differently by intracellular nucleotides.

Modulation of the serotonin-activated K+ channel by G protein subunits and nucleotides in rat hippocampal neurons.

In hippocampal neurons, 5-hydroxytryptamine (5-HT) activates an inwardly rectifying K+ current via G protein. We identified the K+ channel activated by 5-HT (K5-HT channel) and studied the effects of G protein subunits and nucleotides on the K+ channel kinetics in adult rat hippocampal neurons. In inside-out patches with 10 microM 5-HT in the pipette, application of GTP (100 microM) to the cytoplasmic side of the membrane activated an inwardly rectifying K+ channel with a slope conductance of 36 +/- 1 pS (symmetrical 140 mM K+) at -60 mV and a mean open time of 1.1 +/- 0.1 msec (n = 5). Transducin beta gamma activated the K5-HT channels and this was reversed by alpha-GDP. Whether the K5-HT channel was activated endogenously (GTP, GTP gamma S) or exogenously (beta gamma), the presence of 1 mM ATP resulted in a approximately 4-fold increase in channel activity due in large part to the prolongation of the open time duration. These effects of ATP were irreversible and not mimicked by AMPPMP, suggesting that phosphorylation might be involved. However, inhibitors of protein kinases A and C (H-7, staurosporine) and tyrosine kinase (tyrphostin 25) failed to block the effect of ATP. These results show that G beta gamma activates the G protein-gated K+ channel in hippocampal neurons, and that ATP modifies the gating kinetics of the channel, resulting in increased open probability via as yet unknown pathways.

Responses of feline raphespinal neurons to urinary bladder distension.

Effects of distending the urinary bladder were studied on extracellular activity of 77 raphespinal neurons in 19 alpha-chloralose anesthetized cats. Neurons were activated antidromically from thoracic spinal cord; recording sites were located in nucleus raphe magnus (NRM). Mean conduction velocity was 48 +/- 2 m/s. Urinary bladder distension (UBD) increased activity in 12 cells and decreased activity in 17 cells. Spontaneous bladder contractions also affected activity in raphespinal neurons responsive to UBD. Noxious pinch stimulus applied to proximal hindlimbs or forelimbs either increased or decreased activity in 28 raphespinal neurons. No cells were excited both by UBD and pinching of skin and deep tissues of the limbs. Thus, excitatory viscerosomatic convergence was not observed with the stimuli tested in raphespinal neurons examined in this study. Urinary bladder input to descending projection neurons in NRM might participate in descending modulation of dorsal horn neurons. In addition, micturition reflexes might be affected by urinary bladder input to these neurons.

Cardiac and abdominal vagal afferent inhibition of primate T9-S1 spinothalamic cells.

Effects of electrically stimulating vagal afferents were determined on lumbosacral spinothalamic tract (STT) neurons in the T9-S1 segments. Stimulating left or right vagal afferents inhibited 20 (50%) and excited 4 (10%) of 40 STT neurons. Vagal stimulation reduced activity of the 20 inhibited cells by 71 +/- 6% and reduced the average activity of all 40 STT neurons by 28% from 11.5 +/- 1.3 to 8.3 +/- 1.4 impulses/s (P less than 0.01). Effects of activating thoracic and abdominal or just abdominal vagal afferents were also determined. Stimulating right abdominal vagal afferents inhibited 4 (11%), excited 1 (3%), and did not affect 30 (86%) of the STT neurons and overall did not significantly affect STT cell activity. In contrast, in 33 of these cells stimulation of afferents in the right cervical vagus inhibited 16 (48%), excited 2 (6%), and did not affect 15 (45%) neurons and overall significantly reduced cell activity by 29% (P less than 0.01). These data and those of Ammons et al. (J. Neurophysiol. 50: 926-940, 1983; Circ Res. 53: 603-612, 1983; J. Neurophysiol. 54: 73-89, 1985) suggest that cardiopulmonary but not abdominal vagal afferent input reduces STT cell activity in many spinal segments. This inhibitory vagal reflex may play a role in protecting the heart.

Urinary bladder and hindlimb afferent input inhibits activity of primate T2-T5 spinothalamic tract neurons.

1. Extracellular recordings were made from 41 spinothalamic tract (STT) neurons on the left side of the T2-T5 spinal segments of 20 monkeys (Macaca fascicularis) anesthetized with alpha-chloralose. Manipulation of the left triceps-chest region and electrical stimulation of cardiopulmonary sympathetic afferent fibers excited these cells. 2. Isotonic urinary bladder distensions (UBD) to pressures between 20 and 80 cmH2O reduced the spontaneous activity in 33 of 41 cells. Cell activity was significantly reduced by UBD at 20 cmH2O. Distensions to 40, 60, and 80 cmH2O produced progressively greater reductions in spontaneous discharge. Activity was decreased throughout distension in 29 cells (tonic inhibition) and at the onset of distension in 3 neurons (phasic inhibition). In one cell, inhibition followed a brief excitation at the onset of distension (phasic excitation-tonic inhibition). Spontaneous bladder contractions also inhibited STT cell activity. 3. Inhibition by UBD was observed in STT cells characterized as wide dynamic range, high threshold, and high threshold inhibitory. No correlation existed between cell type or laminar location and inhibition by urinary bladder distension. Cells excited by cardiopulmonary sympathetic afferent A delta- and C-fibers had a significantly greater tendency to be inhibited by UBD (17 of 18) than cells activated by A delta- but not C-fibers (13 of 20). 4. Urinary bladder distension and pinch of the hindlimbs also reduced activity of STT cells excited by input from cardiopulmonary sympathetic afferents and from the proximal forelimb. 5. Urinary bladder distension to 40, 60, or 80 cmH2O produced a greater absolute but smaller relative reduction in the firing frequency of STT cells as spontaneous activity increased. Thus the magnitude of this inhibitory effect may depend on whether the inhibitory effect is measured as an absolute or relative change in cell activity. 6. Convergent inhibitory input from somatic regions also was observed. Noxious pinch of the hamstring region of the right hindlimb decreased activity in 32 of 39 cells. Left hindlimb pinch inhibited 21 of 38 cells, and 15 of 29 cells were inhibited by right triceps pinch. 7. Convergent inhibitory input from the hamstring region of the hindlimbs and from the urinary bladder to upper thoracic STT cells may be important for coding the intensity and location of noxious visceral and somatic stimuli and for organizing the appropriate sequence of motor responses when multiple noxious stimuli are present.