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The pathophysiological processes leading to epilepsy are poorly understood. Understanding the molecular and cellular mechanisms involved in the onset of epilepsy is crucial for drug development. Epileptogenicity is thought to be associated with changes in synaptic plasticity; however, whether extracellular matrix molecules-known regulators of synaptic plasticity-are altered during epileptogenesis is unknown. To test this, we used a pentylenetetrazole- (PTZ-) kindling model mouse to investigate changes to hippocampal parvalbumin- (PV-) positive neurons, extracellular matrix molecules, and perineuronal nets (PNNs) after the last kindled seizure. We found an increase in Wisteria floribunda agglutinin- (WFA-) and Cat-315-positive PNNs and a decrease in PV-positive neurons not surrounded by PNNs, in the hippocampus of PTZ-kindled mice compared to control mice. Furthermore, the expression of WFA- and Cat-315-positive molecules increased in the extracellular space of PTZ-kindled mice. In addition, consistent with previous studies, astrocytes were activated in PTZ-kindled mice. We propose that the increase in PNNs after kindling decreases neuroplasticity in the hippocampus and helps maintain the neural circuit for recurrent seizures. This study shows that possibility of changes in extracellular matrix molecules due to astrocyte activation is associated with epilepticus in PTZ-kindled mice., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2019 Hiroshi Ueno et al.)

Neurons in sensory, sympathetic, and parasympathetic ganglia are surrounded by satellite glial cell (SGCs). There is little information on the effects of nerve damage on SGCs in autonomic ganglia. We studied the consequences of damage to sympathetic nerve terminals by 6-hydroxydopamine (6-OHDA) on SGCs in the mouse superior cervical ganglia (Sup-CG). Immunostaining revealed that at 1-30 d post-6-OHDA injection, SGCs in Sup-CG were activated, as assayed by upregulation of glial fibrillary acidic protein. Intracellular labeling showed that dye coupling between SGCs around different neurons increased 4-6-fold 1-14 d after 6-OHDA injection. Behavioral testing 1-7 d post-6-OHDA showed that withdrawal threshold to tactile stimulation of the hind paws was reduced by 65-85%, consistent with hypersensitivity. A single intraperitoneal injection of the gap junction blocker carbenoxolone restored normal tactile thresholds in 6-OHDA-treated mice, suggesting a contribution of SGC gap junctions to pain. Using calcium imaging we found that after 6-OHDA treatment responses of SGCs to ATP were increased by about 30% compared with controls, but responses to ACh were reduced by 48%. The same experiments for SGCs in trigeminal ganglia from 6-OHDA injected mice showed no difference from controls, confirming that 6-OHDA acted selectively on sympathetic nerves. However, systemic inflammation induced by lipopolysaccharide did not affect SGCs of Sup-CG, but did influence SGCs in trigeminal ganglia in the same manner as 6-OHDA did on SGCs in Sup-CG. We conclude that even though SGCs in sympathetic and sensory ganglia are morphologically similar, they are quite different functionally, particularly after damage., (Copyright © 2019. Published by Elsevier B.V.)

Abnormal neuronal activity in sensory ganglia contributes to chronic pain. There is evidence that signals can spread between cells in these ganglia, which may contribute to this activity. Satellite glial cells (SGCs) in sensory ganglia undergo activation following peripheral injury and participate in cellular communication via gap junctions and chemical signaling. Nitric oxide (NO) is released from neurons in dorsal root ganglia (DRG) and induces cyclic GMP (cGMP) production in SCGs, but its role in SGC activation and neuronal excitability has not been explored. It was previously reported that induction of intestinal inflammation with dinitrobenzoate sulfonate (DNBS) increased gap junctional communications among SGCs, which contributed to neuronal excitability and pain. Here we show that DNBS induced SGC activation in mouse DRG, as assayed by glial fibrillary acidic protein upregulation. DNBS also upregulated cGMP level in SGCs, consistent with NO production. In vitro studies on intact ganglia from DNBS-treated mice showed that blocking NO synthesis inhibited both SGCs activation and cGMP upregulation, indicating an ongoing NO production. Application of NO donor in vitro induced SGC activation, augmented gap junctional communications, and raised neuronal excitability, as assessed by electrical recordings. The cGMP analog 8-Br-cGMP mimicked these actions, confirming the role of the NO-cGMP pathway in intraganglionic communications. NO also augmented Ca 2+ waves propagation in DRG cultures. It is proposed that NO synthesis in DRG neurons increases after peripheral inflammation and that NO induces SGC activation, which in turn contributes to neuronal hyperexcitability. Thus, NO plays a major role in neuron-SGC communication., (© 2019 Wiley Periodicals, Inc.)

Tanezumab, a humanized monoclonal anti-NGF antibody, has demonstrated efficacy and safety profiles in Phase III clinical trials of chronic pain. In a 24-week study in non-human primates, morphological observations of sympathetic ganglia showed decreased ganglia volume, decreased neuronal size, and increased glial cell density compared with controls after 3 tanezumab treatments. Using stereological techniques to quantify glial cells, the present 26-week study found no significant difference after weekly treatments in total cervicothoracic ganglia satellite glial cell number between placebo- or tanezumab-treated cynomolgus monkeys. These findings suggest that tanezumab treatment does not result in a true gliosis in sympathetic ganglia., (Copyright © 2019. Published by Elsevier B.V.)

Pruritus is a common and disabling symptom in patients with hepatobiliary disorders, particularly in those with cholestatic features. Serum levels of lysophosphatidic acid (LPA) and its forming enzyme autotaxin were increased in patients suffering from hepatic pruritus, correlated with itch severity and response to treatment. Here we show that in a culture of dorsal root ganglia LPA 18:1 surprisingly activated a large fraction of satellite glia cells, and responses to LPA 18:1 correlated inversely with responses to neuronal expressed transient receptor potential channels. LPA 18:1 caused only a marginal activation of heterologously expressed TRPV1, and responses in dorsal root ganglion cultures from TRPV1-deficient mice were similar to controls. LPA 18:1 desensitized subsequent responsiveness to chloroquine and TGR5 agonist INT-777. The LPA 18:1-induced increase in cytoplasmatic calcium stems from the endoplasmatic reticulum. LPA receptor expression in dorsal root ganglia and Schwann cells, LPAR1 immunohistochemistry, and pharmacological results indicate a signaling pathway through LPA receptor 1. Peripheral rat Schwann cells, which are of glial lineage as the satellite glia cells, were also responsive to LPA 18:1. Summarizing, LPA 18:1 primarily activates rather glial cells than neurons, which may subsequently modulate neuronal responsiveness and sensory sensations such as itch and pain., (© 2019 Wiley Periodicals, Inc.)

Satellite glial cells (SGCs) surround the neurons in sympathetic ganglia and are believed to make important contributions to the function of the ganglia under normal and pathological conditions. It has been proposed that SGCs communicate chemically with the neurons, but little is known about their pharmacological properties and there is no information on whether they respond to acetylcholine (ACh), which is the major neurotransmitter in these ganglia. We used calcium imaging to examine responses of SGCs in the mouse superior cervical ganglion to ACh. The SGCs responded to ACh (0.01-2 mM) with an elevation of intracellular Ca 2+ , which appeared to be due to direct action on these cells, as the response persisted in the presence of the nerve blocker tetrodotoxin (1 μM). The response was largely inhibited by atropine, indicating an action on muscarinic ACh receptors. In contrast to this, sensory ganglia (nodose and trigeminal) were not sensitive to ACh. Incubation of the ganglia in ACh (0.5 or 1 mM) increased the expression of glial fibrillay acidic protein, which is a marker for glial activation. Such incubation also increased the electrical coupling of SGCs, which is known to occur in sensory ganglia following injury. We conclude that SGCs in the superior cervical ganglia display muscarinic ACh receptors, which enable them to communicate chemically with the sympathetic neurons., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The mechanisms of chronic postsurgical pain remain to be elucidated. We reported here that skin/muscle incision and retraction (SMIR), a rat model of postsurgical pain, phosphorylated the extracellular regulated protein kinases (ERK) signaling components c-Raf, MEK (ERK kinase) and ERK1/2 in lumbar 3 dorsal root ganglion (L3 DRG) in rats. Intrathecal injection of ERK specific inhibitor SCH772984 suppressed the mechanical allodynia induced by SMIR. Furthermore, SMIR upregulated tumor necrosis factor alpha (TNFα) in L3 DRG, which could be inhibited by SCH772984. Intrathecal injection of TNF antagonist Etanercept could also inhibit the mechanical allodynia and the increased ERK phosphorylation in L3 DRG induced by SMIR. In addition, immunofluorescent data showed that P2X7R was located exclusively in GFAP labeled satellite glial cells and was highly colocalized with p-ERK1/2 following SMIR. Pretreatment with P2X7R antagonist Brilliant Blue G (BBG) could also block the mechanical allodynia, inhibited the phosphorylation of c-Raf, MEK, ERK1/2, and decrease the expression of TNF-α. Finally, intrathecal injection of BzATP produced mechanical allodynia and induced ERK phosphorylation in satellite glial cells in L3 DRG. Thus, P2X7R activation in satellite glial cells in L3 DRG, leading to a positive feedback between ERK pathway activation and TNF-α production, is suggested to be involved in the induction of chronic postsurgical pain following SMIR., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Endothelins (ET) are a family of highly active neuropeptides with manifold influences via ET receptors (ETR) in both the peripheral and central nervous systems. We have shown previously that satellite glial cells (SGCs) in mouse trigeminal ganglia (TG) are extremely sensitive to ET-1 in evoking [Ca 2+ ] in increase, apparently via ET B R activation, but there is no functional information on ETR in SGCs of other peripheral ganglia. Here we tested the effects of ET-1 on SGCs in nodose ganglia (NG), which is sensory, and superior cervical ganglia (Sup-CG), which is part of the sympathetic nervous system, and further investigated the influence of ET-1 on SGCs in TG. Using calcium imaging we found that SGCs in intact, freshly isolated NG and Sup-CG are highly sensitive to ET-1, with threshold concentration at 0.1nM. Our results showed that [Ca 2+ ] in elevation in response to ET-1 was partially due to Ca 2+ influx from the extracellular space and partially to Ca 2+ release from intracellular stores. Using receptor selective ETR agonists and antagonists, we found that the responses were mediated by mixed ET A R/ET B R in SGCs of NG and predominantly by ET B R in SGCs of Sup-CG. By employing intracellular dye injection we examined coupling among SGCs around different neurons in the presence of 5nM ET-1 and observed coupling inhibition in all the three ganglion types. In summary, our work showed that SGCs in mouse sensory and sympathetic ganglia are highly sensitive to ET-1 and that this peptide markedly reduces SGCs coupling. We conclude that ET-1, which may participate in neuron-glia communications, has similar functions in wide range of peripheral ganglia., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Pituitary adenylyl cyclase-activating polypeptide (PACAP) is a bioactive peptide with diverse effects in the nervous system. The present study investigated whether stimulation of PACAP receptors (PACAPRs) induces responses in neurons and satellite cells of the superior cervical ganglia (SCG), with special reference to intracellular Ca 2+ ([Ca 2+ ] i ) changes. The expression of PACAPRs in SCG was detected by reverse transcription-PCR. PACAP type 1 receptor (PAC1R), vasoactive intestinal peptide receptor type (VPAC)1R, and VPAC2R transcripts were expressed in SCG, with PAC1R showing the highest levels. Confocal microscopy analysis revealed that PACAP38 and PACAP27 induced an increase in [Ca 2+ ] i in SCG, first in satellite cells and subsequently in neurons. Neither extracellular Ca 2+ removal nor Ca 2+ channel blockade affected the PACAP38-induced increase in [Ca 2+ ] i in satellite cells; however, this was partly inhibited in neurons. U73122 or xestospongin C treatment completely and partly abrogated [Ca 2+ ] i changes in satellite cells and in neurons, respectively, whereas VPAC1R and VPAC2R agonists increased [Ca 2+ ] i in satellite cells only. This is the first report demonstrating the expression of PACAPRs specifically, VPAC1 and VPAC2 in SCG and providing evidence for PACAP38-induced [Ca 2+ ] i changes in both satellite cells and neurons via Ca 2+ mobilization.

Lipopolysaccharide (LPS) has been used extensively to study neuroinflammation, but usually its effects were examined acutely (24h<). We have shown previously that a single intraperitoneal LPS injection activated satellite glial cells (SGCs) in mouse dorsal root ganglia (DRG) and altered several functional parameters in these cells for at least one week. Here we asked whether the LPS effects would persist for 1 month. We injected mice with a single LPS dose and tested pain behavior, assessed SGCs activation in DRG using glial fibrillary acidic protein (GFAP) immunostaining, and injected a fluorescent dye intracellularly to study intercellular coupling. Electron microscopy was used to quantitate changes in gap junctions. We found that at 30 days post-LPS the threshold to mechanical stimulation was lower than in controls. GFAP expression, as well as the magnitude of dye coupling among SGCs were greater than in controls. Electron microscopy analysis supported these results, showing a greater number of gap junctions and an abnormal growth of SGC processes. These changes were significant, but less prominent than at 7 days post-LPS. We conclude that a single LPS injection exerts long-term behavioral and cellular changes. The results are consistent with the idea that SGC activation contributes to hyperalgesia., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Unlabelled: Long-term potentiation of excitatory synapses on pyramidal neurons in the stratum radiatum rarely occurs in hippocampal area CA2. Here, we present evidence that perineuronal nets (PNNs), a specialized extracellular matrix typically localized around inhibitory neurons, also surround mouse CA2 pyramidal neurons and envelop their excitatory synapses. CA2 pyramidal neurons express mRNA transcripts for the major PNN component aggrecan, identifying these neurons as a novel source for PNNs in the hippocampus. We also found that disruption of PNNs allows synaptic potentiation of normally plasticity-resistant excitatory CA2 synapses; thus, PNNs play a role in restricting synaptic plasticity in area CA2. Finally, we found that postnatal development of PNNs on CA2 pyramidal neurons is modified by early-life enrichment, suggesting that the development of circuits containing CA2 excitatory synapses are sensitive to manipulations of the rearing environment., Significance Statement: Perineuronal nets (PNNs) are thought to play a major role in restricting synaptic plasticity during postnatal development, and are altered in several models of neurodevelopmental disorders, such as schizophrenia and Rett syndrome. Although PNNs have been predominantly studied in association with inhibitory neurons throughout the brain, we describe a dense expression of PNNs around excitatory pyramidal neurons in hippocampal area CA2. We also provide insight into a previously unrecognized role for PNNs in restricting plasticity at excitatory synapses and raise the possibility of an early critical period of hippocampal plasticity that may ultimately reveal a key mechanism underlying learning and memory impairments of PNN-associated neurodevelopmental disorders., (Copyright © 2016 the authors 0270-6474/16/366312-09$15.00/0.)

Communications between satellite glial cells and neighboring neurons within sensory ganglia may contribute to neuropathic and inflammatory pain. To elucidate the role of satellite glial cells in chemotherapy-induced pain, we examined the effects of oxaliplatin on the gap junction-mediated coupling between these cells. We also examined whether the gap junction blocker, carbenoxolone, can reverse the coupling. Primary cultures of mice trigeminal ganglia, 24-48h after cell isolation, were used. Satellite glial cells were injected with Lucifer yellow in the presence or absence of oxaliplatin (60 μM). In addition, the effect of carbenoxolone (100 μM) on coupling, and the expression of connexin 43 proteins were evaluated. Dye coupling between adjacent satellite glial cells was significantly increased (2.3-fold, P<0.05) following a 2h incubation with oxaliplatin. Adding carbenoxolone to the oxaliplatin-treated cultures reversed oxaliplatin-evoked coupling to baseline (P<0.05). Immunostaining showed no difference between expression of connexin 43 in control and oxaliplatin-treated cultures. Our findings indicated that oxaliplatin-increased gap junction-mediated coupling between satellite glial cells in primary cultures of mouse trigeminal ganglia, and carbenoxolone reversed this effect. Hence, it is proposed that increased gap junction-mediated coupling was seen between satellite glial cells in TG. This observation together with our previous data obtained from a behavioral study suggests that this phenomenon might contribute to chemotherapy-induced nociception following oxaliplatin treatment., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Trigeminal (TG) pain often lacks a satisfactory pharmacological control. A better understanding of the molecular cross-talk between TG neurons and surrounding satellite glial cells (SGCs) could help identifying innovative targets for the development of more effective analgesics. We have previously demonstrated that neuronal pro-algogenic mediators upregulate G protein-coupled nucleotide P2Y receptors (P2YRs) expressed by TG SGCs in vitro. Here, we have identified the specific P2YR subtypes involved (i.e., the ADP-sensitive P2Y1 R and the UTP-responsive P2Y2 R subtypes), and demonstrated the contribution of neuron-derived prostaglandins to their upregulation. Next, we have translated these data to an in vivo model of TG pain (namely, rats injected with Complete Freund's adjuvant in the temporomandibular joint), by demonstrating activation of SGCs and upregulation of P2Y1 R and P2Y2 R in the ipsi-lateral TG. To unequivocally link P2YRs to the development of facial allodynia, we treated animals with various purinergic antagonists. The selective P2Y2 R antagonist AR-C118925 completely inhibited SGCs activation, exerted a potent anti-allodynic effect that lasted over time, and was still effective when administration was started 6-days post induction of allodynia, i.e. under subchronic pain conditions. Conversely, the selective P2Y1 R antagonist MRS2179 was completely ineffective. Moreover, similarly to the anti-inflammatory drug acetylsalicylic acid and the known anti-migraine agent sumatriptan, the P2X/P2Y nonselective antagonist PPADS was only partially effective, and completely lost its activity under sub-chronic conditions. Taken together, our results highlight glial P2Y2 Rs as potential "druggable" targets for the successful management of TG-related pain., (© 2015 Wiley Periodicals, Inc.)

Cisplatin, oxaliplatin, paclitaxel, vincristine and bortezomib are some of the most effective drugs successfully employed (alone or in combinations) as first-line treatment for common cancers. However they often caused severe peripheral neurotoxicity and neuropathic pain. Structural deficits in Dorsal Root Ganglia and sensory nerves caused symptoms as sensory loss, paresthesia, dysaesthesia and numbness that result in patient' suffering and also limit the life-saving therapy. Several scientists have explored the various mechanisms involved in the onset of chemotherapy-related peripheral neurotoxicity identifying molecular targets useful for the development of selected neuroprotective strategies. Dorsal Root Ganglia sensory neurons, satellite cells, Schwann cells, as well as neuronal and glial cells in the spinal cord, are the preferential sites in which chemotherapy neurotoxicity occurs. DNA damage, alterations in cellular system repairs, mitochondria changes, increased intracellular reactive oxygen species, alterations in ion channels, glutamate signalling, MAP-kinases and nociceptors ectopic activation are among the events that trigger the onset of peripheral neurotoxicity and neuropathic pain. In the present work we review the role of the main players in determining the pathogenesis of anticancer drugs-induced peripheral neuropathy., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

We examined ATP-induced intracellular Ca(2+) ([Ca(2+)]i) responses in the neurons and satellite cells from one of the viscerosensory ganglia, the nodose ganglion (NG), as well as the GABA-mediated modulation of ATP-induced neuronal [Ca(2+)]i responses using intracellular calcium imaging. In neurons with satellite cells, ATP induced [Ca(2+)]i increases in both the neurons and satellite cells. The P2X receptor agonist, α,β-meATP, induced [Ca(2+)]i increases in neurons and this response was inhibited by the P2X receptor antagonist, PPADS. On the other hand, the P2Y receptor agonist, ADP, induced [Ca(2+)]i increases in satellite cells, and this response was inhibited by the P2Y receptor antagonist, MRS2179. RT-PCR detected the expression of P2X2, P2X3, P2Y1, and P2Y2 receptor mRNAs in NG extracts. Immunohistochemistry revealed that NG neurons and satellite cells were immunoreactive to P2X2 and P2X3, and P2Y1 and P2Y2 receptors, respectively. In isolated neurons, the ATP-evoked [Ca(2+)]i increase was inhibited by GABA. However, in neurons with satellite cells, the GABAA receptor antagonist, bicuculline, enhanced the ATP-induced [Ca(2+)]i increase in neurons. These results suggest that viscerosensory neuronal excitability may be modulated by GABA from satellite cells in NG., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

The present study evaluated the role of N-methyl-D-aspartate receptors (NMDARs) expressed in the dorsal root ganglia (DRG) in the inflammatory sensitization of peripheral nociceptor terminals to mechanical stimulation. Injection of NMDA into the fifth lumbar (L5)-DRG induced hyperalgesia in the rat hind paw with a profile similar to that of intraplantar injection of prostaglandin E2 (PGE2), which was significantly attenuated by injection of the NMDAR antagonist D(-)-2-amino-5-phosphonopentanoic acid (D-AP-5) in the L5-DRG. Moreover, blockade of DRG AMPA receptors by the antagonist 6,7-dinitroquinoxaline-2,3-dione had no effect in the PGE2-induced hyperalgesia in the paw, showing specific involvement of NMDARs in this modulatory effect and suggesting that activation of NMDAR in the DRG plays an important role in the peripheral inflammatory hyperalgesia. In following experiments we observed attenuation of PGE2-induced hyperalgesia in the paw by the knockdown of NMDAR subunits NR1, NR2B, NR2D, and NR3A with antisense-oligodeoxynucleotide treatment in the DRG. Also, in vitro experiments showed that the NMDA-induced sensitization of cultured DRG neurons depends on satellite cell activation and on those same NMDAR subunits, suggesting their importance for the PGE2-induced hyperalgesia. In addition, fluorescent calcium imaging experiments in cultures of DRG cells showed induction of calcium transients by glutamate or NMDA only in satellite cells, but not in neurons. Together, the present results suggest that the mechanical inflammatory nociceptor sensitization is dependent on glutamate release at the DRG and subsequent NMDAR activation in satellite glial cells, supporting the idea that the peripheral hyperalgesia is an event modulated by a glutamatergic system in the DRG.

Satellite glial cells (SGCs) surrounding primary sensory neurons are similar to astrocytes of the central nervous system in that they buffer the extracellular environment via potassium and calcium channels and express the intermediate filament glial fibrillary acidic protein (GFAP). Peripheral nerve injury induces a reactive state in SGCs that includes SGC proliferation, increased SGC/SGC coupling via gap junctions, decreased inward rectifying potassium channel 4.1 (Kir 4.1) expression and increased expression of GFAP and the common neurotrophin receptor, p75NTR. In contrast, neuronal p75NTR expression, normally detected in ∼80% of adult rat sensory neurons, decreases in response to peripheral axotomy. Given the differential regulation of p75NTR expression in neurons versus SGCs with injury, we hypothesized that reduced signaling via neuronal p75NTR contributes to the induction of a reactive state in SGCs. We found that reducing neuronal p75NTR protein expression in uninjured sensory neurons by intrathecal subarachnoid infusion of p75NTR-selective anti-sense oligodeoxynucleotides for one week was sufficient to induce a "reactive-like" state in the perineuronal SGCs akin to that normally observed following peripheral nerve injury. This reactive state included significantly increased SGC p75NTR, GFAP and gap junction protein connexin-43 protein expression, increased numbers of SGCs surrounding individual sensory neurons and decreased SGC Kir 4.1 channel expression. Collectively, this supports the tenet that reductions in target-derived trophic support leading to, or as a consequence of, reduced neuronal p75NTR expression plays a critical role in switching the SGC to a reactive state., (Copyright © 2014 Wiley Periodicals, Inc.)

Because of its high oxygen demands, neural tissue is predisposed to oxidative stress. Here, our aim was to clarify the cellular localization of antioxidant enzymes in the trigeminal ganglion. We found that the transcriptional factor Sox10 is localized exclusively in satellite glial cells (SGCs) in the adult trigeminal ganglion. The use of transgenic mice that express the fluorescent protein Venus under the Sox10 promoter enabled us to distinguish between neurons and SGCs. Although both superoxide dismutases 1 and 2 were present in the neurons, only superoxide dismutase 1 was identified in SGCs. The enzymes relevant to hydrogen peroxide degradation displayed differential cellular localization, such that neurons were endowed with glutathione peroxidase 1 and thioredoxin 2, and catalase and thioredoxin 2 were present in SGCs. Our immunohistochemical finding showed that only SGCs were labeled by the oxidative damage marker 8-hydroxy-2'-deoxyguanosine, which indicates that the antioxidant systems of SGCs were less potent. The transient receptor potential vanilloid subfamily member 1 (TRPV1), the capsaicin receptor, is implicated in inflammatory hyperalgesia, and we demonstrated that topical capsaicin application causes short-lasting mechanical hyperalgesia in the face. Our cell-based assay revealed that TRPV1 agonist stimulation in the presence of TRPV1 overexpression caused reactive oxygen species-mediated caspase-3 activation. Moreover, capsaicin induced the cellular demise of primary TRPV1-positive trigeminal ganglion neurons in a dose-dependent manner, and this effect was inhibited by a free radical scavenger and a pancaspase inhibitor. This study delineates the localization of antioxidative stress-related enzymes in the trigeminal ganglion and reveals the importance of the pivotal role of reactive oxygen species in the TRPV1-mediated caspase-dependent cell death of trigeminal ganglion neurons. Therapeutic measures for antioxidative stress should be taken to prevent damage to trigeminal primary sensory neurons in inflammatory pain disorders., (Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.)

To clarify the role of angiotensin II (Ang II) in the regulation of sensory signaling, we studied the effect of subpressor dose (150 ng/kg/min) of Ang II on pain-related behavior in relation with neuronal injury and activation of satellite glial cells (SGCs) in the dorsal root ganglia (DRGs) after chronic constriction injury (CCI). Systemic continuous delivery of Ang II induced the tactile, heat and cold hyperlagesia, when measured at 7 days ofpost-injury. Blockade of the AT1 receptor with losartan (2.5 mg/kg/day) prevented tactile hyperalgesia and attenuated cold hyperalgesia, but did not affect the response to noxious heat stimulus. A marked increase of large-sized injured primary afferent neurons, detected by ATF3 immunolabeling, was seen in lower lumbar DRGs on ipsilateral side after Ang II treatment. Subpressor dose of Ang II induced an increase of activated SGCs (detected by GFAP immunolabeling) enveloping large-diameter neurons. Our results suggested that Ang II through the AT1 receptor activation is an important regulatory factor in neuropathic pain perception and plays an important role in the injury of large-sized primary afferent neurons and activation of SGCs elicited by the CCI.

Satellite glia cells (SGCs), within the dorsal root ganglia (DRG), surround the somata of most sensory neurons. SGCs have been shown to interact with sensory neurons and appear to be involved in the processing of afferent information. We found that in rat DRG various N-methyl-D-aspartate receptor (NMDAr) subunits were expressed in SGCs in intact ganglia and in vitro. In culture, when SGCs were exposed to brief pulses of NMDA they evoked transient increases in cytoplasmic calcium that were inhibited by specific NMDA blockers (MK-801, AP5) while they were Mg²⁺ insensitive indicating that SGCs express functional NMDAr. The percentage of NMDA responsive SGCs was similar in mixed- (SGCs plus neurons) and SGC-enriched cultures. The pattern of the magnitude changes of the NMDA-evoked response was similar in SGCs and DRG neurons when they were in close proximity, suggesting that the NMDA response of SGCs and DRG neurons is modulated by their interactions. Treating the cultures with nerve growth factor, and/or prostaglandin E₂ did not alter the percentage of SGCs that responded to NMDA. Since glutamate appears to be released within the DRG, the detection of functional NMDAr in SGCs suggests that their NMDAr activity could contribute to the interactions between neurons and SGCs. In summary we demonstrated for the first time that SGCs express functional NMDAr., (Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.)

Background: Chemotherapy-induced peripheral neuropathy is a serious side effect in cancer treatment, a major manifestation being neuropathic pain that can be debilitating and can reduce the quality of life of the patient. Oxaliplatin and taxol are common anti-cancer drugs that induce neuropathic pain by an unknown mechanism. We tested the hypothesis that satellite glial cells in dorsal root ganglia (DRGs) are altered in chemotherapy-induced peripheral neuropathy models and contribute to neuropathic pain., Methods: Mice were injected with either oxaliplatin or taxol and examined at 7-30 days. Glial fibrillary acidic protein (glial activation marker) expression was determined by immunohistochemistry. Satellite glial cells in isolated DRG were injected with the fluorescent dye Lucifer yellow and the incidence of dye coupling among these cells that surround different neurons was quantified., Results: Taxol or oxaliplatin increased glial fibrillary acidic protein expression in satellite glial cells. Gap junction-mediated coupling between satellite glial cells was increased by up to fivefold after oxaliplatin and by up to twofold after taxol. This is consistent with work on other pain models showing that augmented satellite glial cell coupling contributes to chronic pain. Administration of the gap junction blocker carbenoxolone to chemotherapy-treated mice produced an analgesic-like effect., Conclusions: We propose that increased coupling by gap junctions is part of satellite glial cell activation, and that augmented coupling contributes to the lowering of pain threshold in oxaliplatin- and taxol-treated mice. We further propose that gap junction blockers may have potential in treating chemotherapy-induced neuropathic pain., (© 2012 European Federation of International Association for the Study of Pain Chapters.)

The role of satellite glial cells (SGCs) of sensory ganglia in chronic pain begins to receive interest. The present study aims to investigate the contribution of SGC activation to the development of neuropathic pain. A neuropathic pain model was established by lumbar 5 spinal nerve ligation (SNL), and glial fibrillary acidic protein (GFAP) was used as a marker of SGC activation. It was found that SGCs were activated in the ipsilateral dorsal root ganglia (DRG) increased significantly as early as 4h following SNL, gradually increased to a peak level at day 7, and then stayed at a high level to the end of the experiment at day 56. SGC activation in the SNL group was significantly higher than that in the sham group at days 1, 3 and 7 after operation. Immunofluorescent double labeling showed that the activated SGCs encircled large, medium-sized and small neurons. The SGCs surrounded the small and medium-sized neurons were preferentially activated in the early phase, but shifted to large diameter neurons as time went on. Continuous infusion of fluorocitrate, a glial metabolism inhibitor, to the affected DRG via mini-osmotic pump for 7d significantly alleviated mechanical allodynia at day 7. These results suggest that SGCs in the DRG were activated after SNL. SGC activation contributed to the early maintenance of neuropathic pain., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Objective: To evaluate the effect of tetrandrine (Tet) on nitroglycerin(GTN)-induced activation of the satellite cells released inflammatory cytokines and to explore its mechanism., Method: Neonatal rat satellite cells of trigeminal ganglia were cultured and separated into three groups. Group CON: the cells were normal cultured; Group TGN: the cells were cultured with 0.55 mmol x L(-1) GTN; Group Tet: the cells were treated with 0.55 mmol x L(-1) GTN and 1 x 10(-7) mol x L(-1) Tet respectively. Cell viability after GTN and Tet was detected by AlamarBlue assay. The concentration change of intracellular Ca2+ ([Ca2+]i) in single satellite cell loaded with Fluo-3/AM was determined by laser scanning confocal microscopy. NF-kappaB and IL-1beta mRNA levels were determined by FQ-PCR. Through double-immunofluorescent staining identifies satellite cells and determines the expression of NF-kappaB protein., Result: Satellite cells activities decreased with GTN stimulating, but according to the viability and modality of the cells, 1 x 10(-7) mol x L(-1) Tet was the suitable prophylaxis. Tet can inhibit the elevation of cytosolic free calcium of rat satellite cell and decrease the mRNA and protein levels of NF-kappaB and the mRNA levels of IL-1beta., Conclusion: Via preventing Ca2+ influxion, Tet inhibited NF-kappaB activation of satellite cell which decreased IL-1beta expression.

In the present paper, we have further developed an in vitro model to study neuronal-glial interaction at trigeminal level by characterizing the effects of conditioned medium (CM) collected from activated primary cultures of satellite glial cells (SGCs) on calcitonin gene-related peptide (CGRP) release from rat trigeminal neurons. Moreover, we investigated whether such release is inhibited by a clinically relevant anti-migraine drug, sumatriptan. CM effects were tested on trigeminal neuronal cultures in different conditions of activation and at different time points. Long-term exposures of trigeminal neurons to CM increased directly neuronal CGRP release, which was further enhanced by the exposure to capsaicin. In this framework, the anti-migraine drug sumatriptan was able to inhibit the evoked CGRP release from naïve trigeminal neuron cultures, as well as from trigeminal cultures pre-exposed for 30 min to CM. On the contrary, sumatriptan failed to inhibit evoked CGRP release from trigeminal neurons after prolonged (4 and 8 h) pre-exposures to CM. These findings were confirmed in co-culture experiments (neurons and SGCs), where activation of SGCs or a bradykinin priming were used. Our data demonstrate that SGCs activation could influence neuronal excitability, and that this event affects the neuronal responses to triptans.

Neurogenic inflammation is induced by inflammatory mediators released in peripheral tissue from primary afferent nociceptors. Our previous studies suggest that neurogenic inflammation induced by intradermal injection of capsaicin results from the enhancement of dorsal root reflexes (DRRs), which involve antidromic activation of dorsal root ganglion (DRG) neurons. Numerous studies have reported the important role of glial modulation in pain. However, it remains unclear whether glial cells participate in the process of neurogenic inflammation-induced pain. Here we tested the role of DRG satellite glial cells (SGCs) in this process in anesthetized rats by administration of a glial inhibitor, minocycline. Electrical stimuli (ES, frequency 10 Hz; duration 1 ms; strength 3 mA) were applied to the cut distal ends of the L4-5 dorsal roots. The stimuli evoked antidromic action potentials designed to mimic DRRs. Local cutaneous blood flow in the hindpaw was measured using a Doppler flow meter. Antidromic ES for 10 min evoked a significant vasodilation that could be inhibited dose-dependently by local administration of the calcitonin gene-related peptide receptor antagonist, CGRP8-37. Pretreatment with capsaicin intradermally injected into the hindpaw 2h before the ES enhanced greatly the vasodilation evoked by antidromic ES, and this enhancement could be reversed by minocycline pretreatment. Our findings support the view that neurogenic inflammation following capsaicin injection involves antidromic activation of DRG neurons via the generation of DRRs. Inhibition of neurogenic inflammation by minocycline is suggested to be associated with its inhibitory effect on SGCs that are possibly activated following capsaicin injection., ((c) 2010 Elsevier Ireland Ltd. All rights reserved.)

Satellite glial cells in the dorsal root ganglion (DRG), like the better-studied glia cells in the spinal cord, react to peripheral nerve injury or inflammation by activation, proliferation, and release of messengers that contribute importantly to pathological pain. It is not known how information about nerve injury or peripheral inflammation is conveyed to the satellite glial cells. Abnormal spontaneous activity of sensory neurons, observed in the very early phase of many pain models, is one plausible mechanism by which injured sensory neurons could activate neighboring satellite glial cells. We tested effects of locally inhibiting sensory neuron activity with sodium channel blockers on satellite glial cell activation in a rat spinal nerve ligation (SNL) model. SNL caused extensive satellite glial cell activation (as defined by glial fibrillary acidic protein [GFAP] immunoreactivity) which peaked on day 1 and was still observed on day 10. Perfusion of the axotomized DRG with the Na channel blocker tetrodotoxin (TTX) significantly reduced this activation at all time points. Similar findings were made with a more distal injury (spared nerve injury model), using a different sodium channel blocker (bupivacaine depot) at the injury site. Local DRG perfusion with TTX also reduced levels of nerve growth factor (NGF) in the SNL model on day 3 (when activated glia are an important source of NGF), without affecting the initial drop of NGF on day 1 (which has been attributed to loss of transport from target tissues). Local perfusion in the SNL model also significantly reduced microglia activation (OX-42 immunoreactivity) on day 3 and astrocyte activation (GFAP immunoreactivity) on day 10 in the corresponding dorsal spinal cord. The results indicate that early spontaneous activity in injured sensory neurons may play important roles in glia activation and pathological pain.

Background: Sensitization and activation of trigeminal neurons are implicated in the underlying pathology of migraine, acute sinusitis, and allergic rhinitis. Cell bodies of trigeminal neurons that provide sensory innervation of the dura and nasal mucosa reside in the trigeminal ganglion in association with satellite glial cells where they communicate via gap junctions. Gap junctions, channels formed by connexins, modulate the excitability state of both neurons and glia under pathological conditions. Tonabersat, a compound being tested as an antimigraine drug, is thought to block gap junction activity., Objective: To investigate the cellular events within trigeminal ganglia that may account for the significant comorbidity of migraine and rhinosinusitis and determine the effect of tonabersat on neuron-satellite glia communication., Methods: Sprague Dawley rats injected with True Blue were used to localize neuronal cell bodies in the ganglion and study neuron-glia signaling via gap junctions in the trigeminal ganglion. Dye coupling studies were conducted under basal conditions and in response to tumor necrosis factor-alpha injection into the whisker pad and/or capsaicin injection into the eyebrow. Changes in connexin 26 and active p38 levels were determined by immunohistochemistry. In addition, the effect of tonabersat prior to chemical stimulation on gap junction activity and expression of connexins and active p38 was investigated., Results: Injection of tumor necrosis factor-alpha, a cytokine implicated in the pathology of acute sinusitis and allergic rhinitis, into the V2 region was shown to lower the amount of capsaicin required to stimulate neurons located in the V1 region of the ganglion. While injection of tumor necrosis factor-alpha into the whisker pad or capsaicin injection into the eyebrow alone did not cause increased dye movement, the combination of both stimuli greatly increased neuron-satellite glia communication via gap junctions in both V1 and V2 regions. The change in gap junction activity was accompanied by increased expression of connexin 26 and active p38 levels in both neurons and satellite glia in V1 and V2 regions. Pretreatment with tonabersat inhibited gap junction communication between neurons and satellite glia and blocked the increase in connexin 26 and active p38 levels in response to injection of both tumor necrosis factor-alpha (V2) and capsaicin (V1)., Conclusions: We propose that increased levels of tumor necrosis factor-alpha, as reported during acute sinusitis and allergic rhinitis, reduces the amount of capsaicin necessary to stimulate V1 neurons that leads to cellular changes in both V1 and V2 regions. The cellular events observed in this study may help to explain, in part, the significant comorbidity reported with migraine and rhinosinusitis. In addition, we have provided evidence to suggest that tonabersat can prevent increased neuron-satellite glia signaling and, thus, may be useful in the treatment of migraine, acute sinusitis, and allergic rhinitis.

Neurons in dorsal root ganglia (DRG) are surrounded by an envelope of satellite glial cells (SGCs). Little is known about SGC physiology and their interactions with neurons. In this work, we investigated changes in mouse DRG neurons and SGC following the induction of inflammation in the hind paw by the injection of complete Freund's adjuvant (CFA). The electrophysiological properties of neurons were characterized by intracellular electrodes. Changes in coupling mediated by gap junctions between SGCs were monitored using intracellular injection of the fluorescent dye Lucifer yellow. Pain was assessed with von Frey hairs. We found that two weeks after CFA injection there was a 38% decrease in the threshold for firing an action potential in DRG neurons, consistent with neuronal hyperexcitability. Injection of Lucifer yellow into SGCs revealed that, compared with controls, coupling by gap junctions among SGCs surrounding adjacent neurons increased 2.7-, 3.2-, and 2.5-fold one week, two weeks, and one month, respectively, after CFA injection. In SGCs enveloping neurons that project into the inflamed paw this effect was more enhanced (5.4-fold). Interneuronal coupling was augmented by up to 7% after CFA injection. Pain threshold in the injected paw decreased by 13%, 16%, and 11% compared with controls at one week, two weeks, and one month, respectively, after CFA injection. Intraperitoneal injection of the gap junction blocker carbenoxolone prevented the inflammation-induced decrease in pain threshold. The results show that augmented glial coupling is one of the major events occurring in DRG following inflammation. The elevation in pain threshold after carbenoxolone administration provides indirect support for the idea that augmented intercellular coupling might contribute to chronic pain.

Paclitaxel-induced peripheral neuropathy (PN) can be a significant problem for patients receiving chemotherapeutic regimens for the treatment of breast, ovarian, and lung cancer as PN can influence the quality of life and survivorship in these patients. To begin to understand the cellular changes that occur within the peripheral and central nervous system as PN develops, we intravenously infused rats with clinically relevant doses of paclitaxel. Ten days later, behavioral changes indicative of PN became evident that included mechanical allodynia, cold hyperalgesia, and deficits in ambulation/coordination. These behaviors were accompanied by increased expression of activating transcription factor 3 (ATF3; a marker of cellular injury) in a population of large>medium>small diameter sensory neurons, a population of satellite cells in the lumbar dorsal root ganglia (DRG) and in myelinating Schwann cells in the sciatic nerve. In addition, there was an increase in the expression of glial fibrillary acidic protein (GFAP) in DRG satellite cells and an increase in the number of CD68 positive activated macrophages within the DRG and peripheral nerve. Within lamina III-IV of the lumbar spinal cord, there was an increase in OX42 positive microglia. These data suggest that intravenous infusion of paclitaxel induces a peripheral neuropathy characterized by injury of neuronal and non-neuronal cells in the peripheral nervous system, macrophage activation in both the DRG and peripheral nerve, and microglial activation within the spinal cord. An understanding of the factors involved in the development and maintenance of PN may lead to mechanism based therapies that prevent/treat PN and thus improve the survival and quality of life of patients receiving chemotherapy.

Dorsal root ganglia (DRG) are key elements in sensory signaling under physiological and pathological conditions. Little is known about electrical coupling among cells in these ganglia. In this study, we injected the fluorescent dye Lucifer yellow (LY) into single cells to examine dye coupling in DRG. We found no dye coupling between neurons or between neurons and their attendant satellite glial cells (SGCs). In mouse DRG, we observed that in 26.2% of the cases SGCs that surround a given neuron were dye coupled. In only 3.2% of the cases SGCs that make envelopes around different neurons were coupled. The data from mouse ganglia were very similar to those from rat and guinea pig DRG. The results obtained by injection of the tracer biocytin were very similar to those observed with LY. The coupling incidence within the envelopes increased 3.1-fold by high extracellular pH (8.0), but coupling between envelopes was not affected. Acidic pH (6.8) reduced the coupling. High extracellular K+ (9.4 mM) increased the coupling 2.4-fold and 4.7-fold within and between envelopes, respectively. Low extracellular Ca2+ (0.5, 1.0 mM) partly reversed the effect of high K+ on coupling. The results showed that SGCs in mammalian sensory ganglia are connected by gap junctions. This coupling is very sensitive to changes in pH, and can therefore be modulated under various physiological and pathological conditions. The dependence of the coupling on extracellular K+ and Ca2+ suggests that the permeability of gap junctions can be altered by physiological and pharmacological stimuli.

Neuroglial interactions are most profound during development or damage of nerve tissue. We studied the responses of crayfish stretch receptor neurons (SRN) and satellite glial cells to photosensitization with sulfonated aluminum phthalocyanine Photosens. Although Photosens was localized mainly in the glial envelope, neurons were very sensitive to photodynamic treatment. Photosensitization gradually inhibited and then abolished neuron activity. Neuronal and glial nuclei shrank. Some neurons and glial cells lost the integrity of the plasma membrane and died through necrosis after the treatment. The nuclei of other glial cells but not neurons become fragmented, indicating apoptosis. The number of glial nuclei around neuron soma increased, probably indicating proliferation for enhanced neuron protection. Adenylate cyclase (AC) inhibition by MDL-12330A, or tyrosine kinase (TK) inhibition by genistein, shortened neuron lifetime, whereas AC activation by forskolin or protein tyrosine phosphatases (PTP) inhibition by sodium orthovanadate prolonged neuronal activity. Therefore, cAMP and phosphotyrosines produced by AC and TK, respectively, protected SRN against photoinactivation. AC inhibition reduced photodamage of the plasma membrane and subsequent necrosis in neuronal and glial cells. AC activation prevented apoptosis in photosensitized glial cells and stimulated glial proliferation. TK inhibition protected neurons but not glia against photoinduced membrane permeabilization and subsequent necrosis whereas PTP inhibition more strongly protected glial cells. Therefore, both signaling pathways involving cAMP and phosphotyrosines might contribute to the maintenance of neuronal activity and the integrity of the neuronal and glial plasma membranes. Adenylate cyclase but not phosphotyrosine signaling pathways modulated glial apoptosis and proliferation under photooxidative stress., (Copyright 2004 Wiley-Liss, Inc.)

Damage to peripheral nerves induces ectopic firing in sensory neurons, which can contribute to neuropathic pain. As most of the information on this topic is on dorsal root ganglia we decided to examine the influence of infra-orbital nerve section on cells of murine trigeminal ganglia. We characterized the electrophysiological properties of neurons with intracellular electrodes. Changes in the coupling of satellite glial cells (SGCs) were monitored by intracelluar injection of the fluorescent dye Lucifer yellow. Electrophysiology of SGCs was studied with the patch-clamp technique. Six to eight days after axotomy, the percentage of neurons that fire spontaneously increased from 1.6 to 12.8%, the membrane depolarized from -51.1 to -45.5 mV, the percentage of cells with spontaneous potential oscillations increased from 19 to 37%, the membrane input resistance decreased from 44.4 to 39.5 MOmega, and the threshold for firing an action potential decreased from 0.61 to 0.42 nA. These changes are consistent with increased neuronal excitability. SGCs were mutually coupled around a given neuron in 21% of the cases, and to SGCs around neighboring neurons in only 4.8% of the cases. After axotomy these values increased to 37.1 and 25.8%, respectively. After axotomy the membrane resistance of SGCs decreased from 101 MOmega in controls to 40 MOmega, possibly due to increased coupling among these cells. We conclude that axotomy affects both neurons and SGCs in the trigeminal ganglion. The increased neuronal excitability and ectopic firing may play a major role in neuropathic pain.

There are many known growth factors/cytokines that induce skeletal muscle satellite cell proliferation. Currently, the signaling mechanisms in which these growth factors/cytokines activate satellite cell proliferation are not completely understood. Here, we sought to determine signaling mechanisms by which leukemia inhibitory factor (LIF) induces satellite cell proliferation in culture. First, we confirmed that LIF induces proliferation of C2C12 immortalized myoblasts and cultured primary rat satellite cells. In addition, we also found that this increase in proliferation can be inhibited by incubation of the cells in tyrphostin AG 490, a specific inhibitor of Janus-activated kinase (JAK) 2 activity. Furthermore, we also found that incubation of the cells at various time points with LIF (10 ng/ml) induces a significant, transient increase in JAK2 phosphorylation, signal transducers and activators of transcription (STAT3) phosphorylation, and STAT3 transcriptional activity. Increases in the STAT3-sensitive endogenous SOC3 protein followed these transient increases in STAT3 activation. In addition, AG 490 inhibited the increase in STAT3 phosphorylation. Finally, LIF did not change the phosphorylation status of extracellular signal-regulated protein kinase (ERK)1/2 or affect the phosphorylation status of Akt/protein kinase B. However, LY-294002, an inhibitor of phosphoinositide 3-kinase, blocked LIF-induced proliferation of satellite cells. These data suggest that LIF induces satellite cell proliferation by activation of the JAK2-STAT3 signaling pathway, suggesting that this may be an important pathway in muscle growth and/or hypertrophy.

Suramin is being used either alone, or in combination with other chemotherapeutic agents, in the treatment of hormone-refractory or metastatic prostate cancer. Use of this potentially valuable chemotherapy is limited by a dose-dependent polyneuropathy. It has been difficult in human studies to characterize peripheral suramin toxicity separately from cancer-related neuropathy. To characterize suramin-induced neuropathy in a rat model, adult rats were given either a single dose of 500 mg/kg (high dose) or 50 mg/kg (low dose) weekly suramin for 2 months. Electrophysiology and peroneal/sural nerve morphometry were performed. In high dose animals, neuropathy developed within 2 weeks, most severe in the digital sensory responses (DSR) (p<0.05) and tail and hind limb compound muscle action potential (p<0.001). Histologically, there was evidence of axonal degeneration and axon atrophy. With low dose suramin, the DSR (p<0.05) and tail distal sensory and motor responses (p<0.01) were most severely affected at 2 months. Axonal degeneration was seen in teased fibers from most animals. With TEM, there were abundant characteristic lysosomal inclusion bodies in DRG and Schwann cells. Electrophysiological and histological evidence of peripheral demyelination was rare, being observed in only one animal. Suramin induced a length, dose and time-dependent axonal sensorimotor polyneuropathy associated with axonal degeneration, atrophy, and accumulation of glycolipid lysosomal inclusions.

Insulin-like growth factor-binding proteins (IGFBP) regulate the biological functions of insulin-like growth factors (IGF) and may affect cell growth through IGF-independent actions. Growth factors and hormones have been shown to alter IGFBP production by target cells suggesting that the effects of these factors may be partially mediated by the local production of IGFBP. Growth factors, including IGF-I, transforming growth factor-beta1 (TGF-beta1), and basic fibroblast growth factor (bFGF) have potent effects on satellite cell proliferation and differentiation, and some of these factors have been shown to alter IGFBP production in various cell types. Consequently, some of their actions on muscle satellite cells may be mediated by the local production of IGFBP. In this study, we measured the effects of IGF-I, bFGF, and TGF-beta1 on IGFBP production by primary porcine satellite cell (PSC) cultures after first determining physiologically active concentrations of these growth factors to use according to [3H]thymidine incorporation dose responses. There is little information on the effects of these growth factors on IGFBP production in primary porcine myogenic cells due to the confounding affects of contaminating nonmuscle fibroblasts. Comparative studies show that primary porcine satellite cells produce IGFBP-3 and -5 whereas porcine muscle-derived nonfusing cells (FIB) produce IGFBP-2 and -4 but not IGFBP-3 or -5. Because of this, our investigations have focused on growth factor-induced production of IGFBP-3 and -5 in primary porcine satellite cells cultures. Both IGF-I and bFGF exhibited dose-dependent increases in [3H]thymidine incorporation with increasing concentration from 1 to 50 ng/mL (P < 0.05), whereas TGF-beta1 caused a dose-dependent decrease from 0.01 to 0.5 ng/mL (P < 0.05). When 20 ng/ mL of IGF-I was added to the media, IGFBP-3 was increased approximately 65% (P < 0.05) and IGFBP-5 was increased approximately twofold (P < 0.05). The addition of 0.5 ng/mL TGF-beta1 caused more than a two-fold increase in IGFBP-3 (P < 0.05) and approximately an 80% increase in IGFBP-5 (P < 0.05), whereas 50 ng/ mL of bFGF caused approximately 40% (P < 0.05) and 70% (P < 0.05) increases in IGFBP-3 and -5, respectively. Neither IGFBP-3 nor -5 was detectable in the conditioned media from fibroblasts whether or not IGF-I, TGF- beta1 or bFGF were present. These data suggest that the effects of IGF-I, TGF- beta1 and bFGF on porcine satellite cells may in part be through the autocrine/ paracrine production of IGFBP-3 and -5 by porcine satellite cells.