Cerebral peak alpha frequency reflects average pain severity in a human model of sustained, musculoskeletal pain

Heightened pain sensitivity, the amount of pain experienced in response to a noxious event, is a known risk factor for development of chronic pain. We have previously reported that pain-free, sensorimotor peak alpha frequency (PAF) is a reliable biomarker of pain sensitivity for thermal, prolonged pains lasting tens of minutes. To test whether PAF can provide information about pain sensitivity occurring over clinically relevant timescales (i.e., weeks), EEG was recorded before and while participants experienced a long-lasting pain model, repeated intramuscular injection of nerve growth factor (NGF), that produces progressively developing muscle pain for up to 21 days. We demonstrate that pain-free, sensorimotor PAF is negatively correlated with NGF pain sensitivity; increasingly slower PAF is associated with increasingly greater pain sensitivity. Furthermore, PAF remained stable following NGF injection, indicating that the presence of NGF pain for multiple weeks is not sufficient to induce the PAF slowing reported in chronic pain. In total, our results demonstrate that slower pain-free, sensorimotor PAF is associated with heightened sensitivity to a long-lasting musculoskeletal pain and also suggest that the apparent slowing of PAF in chronic pain may reflect predisease pain sensitivity.NEW & NOTEWORTHY Pain sensitivity, the intensity of pain experienced after injury, has been identified as an important risk factor in the development of chronic pain. Biomarkers of pain sensitivity have the potential to ease chronic pain burdens by preventing disease emergence. In the current study, we demonstrate that the speed of pain-free, sensorimotor peak alpha frequency recorded during resting-state EEG predicts pain sensitivity to a clinically-relevant, human model of prolonged pain that persists for weeks.

Role of nerve growth factor in the trinitrobenzene sulfonic acid-induced colonic hypersensitivity

The majority of patients with digestive disorders display visceral pain. In these troubles, visceral pain threshold is decreased, demonstrating visceral hypersensitivity. There is growing evidence that nerve growth factor (NGF) may function as a mediator of persistent pain states. This hypothesis was tested in a model of colonic hypersensitivity measured by isobaric distension in conscious rats. This study was designed to evaluate (1) the effect of exogenous NGF on colonic pain threshold, (2) the involvement of NGF in trinitrobenzene sulfonic acid (TNBS)-induced colonic hypersensitivity, by testing an anti-NGF antibody, and (3) finally the involvement of sensory nerves on NGF and TNBS effects using rats treated neonatally with capsaicin. Intra-peritoneal injection of NGF (0.1-100 ng/rat) decreased in a dose-related manner colonic pain threshold in naive rats. This effect was reversed by anti-NGF antibody (1/2000; 2 ml/kg). TNBS-induced colonic hypersensitivity was also reversed by anti-NGF antibody (1/2000; 2 ml/kg): 37.7 +/- 1.7 and 17.6 +/- 0.7 mmHg (p<0.01) for anti-NGF antibody- and vehicle-treated group, respectively. Neonatal capsaicin pre-treatment inhibited NGF- and TNBS-induced decrease in colonic pain threshold: 49.4 +/- 5.3 versus 22.3 +/- 1.6 mmHg (p<0.01) for capsaicin versus vehicle in NGF-treated rats and 39.6 +/- 3.3 versus 18.0 +/- 1.0 mm Hg (p<0.001) for capsaicin versus vehicle in TNBS-treated rats. These data suggest that the action of NGF on sensory neurons contributes to the development of visceral hypersensitivity and that anti-NGF strategy may be of some therapeutic benefits in digestive sensory disorders.

Role of nerve growth factor in the trinitrobenzene sulfonic acid-induced colonic hypersensitivity

The majority of patients with digestive disorders display visceral pain. In these troubles, visceral pain threshold is decreased, demonstrating visceral hypersensitivity. There is growing evidence that nerve growth factor (NGF) may function as a mediator of persistent pain states. This hypothesis was tested in a model of colonic hypersensitivity measured by isobaric distension in conscious rats. This study was designed to evaluate (1) the effect of exogenous NGF on colonic pain threshold, (2) the involvement of NGF in trinitrobenzene sulfonic acid (TNBS)-induced colonic hypersensitivity, by testing an anti-NGF antibody, and (3) finally the involvement of sensory nerves on NGF and TNBS effects using rats treated neonatally with capsaicin. Intra-peritoneal injection of NGF (0.1-100 ng/rat) decreased in a dose-related manner colonic pain threshold in naive rats. This effect was reversed by anti-NGF antibody (1/2000; 2 ml/kg). TNBS-induced colonic hypersensitivity was also reversed by anti-NGF antibody (1/2000; 2 ml/kg): 37.7 +/- 1.7 and 17.6 +/- 0.7 mmHg (p<0.01) for anti-NGF antibody- and vehicle-treated group, respectively. Neonatal capsaicin pre-treatment inhibited NGF- and TNBS-induced decrease in colonic pain threshold: 49.4 +/- 5.3 versus 22.3 +/- 1.6 mmHg (p<0.01) for capsaicin versus vehicle in NGF-treated rats and 39.6 +/- 3.3 versus 18.0 +/- 1.0 mm Hg (p<0.001) for capsaicin versus vehicle in TNBS-treated rats. These data suggest that the action of NGF on sensory neurons contributes to the development of visceral hypersensitivity and that anti-NGF strategy may be of some therapeutic benefits in digestive sensory disorders.

Reverse Effects of Tetraarsenic Oxide on the Angiogenesis Induced by Nerve Growth Factor in the Rat Cornea

To compare the antiangiogenic effects of tetraarsenic oxide (As4O6) with those of diarsenic oxide (As2O3) in the rat cornea, rat cornea micropocket assay was conducted to induce angiogenesis by implantation of the pellet contained 1.0 ng of nerve growth factor (NGF). Ten of thirty eyes of Sprague-Dawley rats were randomly assigned to one of three groups, namely, control group (no medication), As2O3 group (50 mg/kg As2O3, PO, s.i.d.), and As4O6 group (50 mg/kg As4O6, PO, s.i.d.). After implantation, the number of new vessels, vessel length and clock hour of neovascularization were examined under the microscope from day 3 to day 7. The area of neovascularization was calculated using a mathematical formula. Although new vessels in control and As2O3 groups were first noticed at day 3, whereas those of As4O6 group were first observed on day 5. The number, length, clock hour of neovascularization and areas of the vessels in As4O6 group showed more significant inhibition than those of control and As2O3 groups from day 5 (P<0.05). However, there were no differences in all parameters between control group and As2O3 group during the entire study period. These results showed that As4O6 had antiangiogenic effects on the new vessels induced by NGF in the rat cornea.

Aluminum, NO, and nerve growth factor neurotoxicity in cholinergic neurons

Several neurotoxic compounds, including Al, NO, and beta-amyloid may contribute to the impairment or loss of brain cholinergic neurons in the course of various neurodegenerative diseases. Genotype and phenotypic modifications of cholinergic neurons may determine their variable functional competency and susceptibility to reported neurotoxic insults. Hybrid, immortalized SN56 cholinergic cells from mouse septum may serve as a model for in vitro cholinotoxicity studies. Differentiation by various combinations of cAMP, retinoic acid, and nerve growth factor may provide cells of different morphologic maturity as well as activities of acetylcholine and acetyl-CoA metabolism. In general, differentiated cells appear to be more susceptible to neurotoxic signals than the non-differentiated ones, as evidenced by loss of sprouting and connectivity, decreases in choline acetyltransferase and pyruvate dehydrogenase activities, disturbances in acetyl-CoA compartmentation and metabolism, insufficient or excessive acetylcholine release, as well as increased expression of apoptosis markers. Each neurotoxin impaired both acetylcholine and acetyl-CoA metabolism of these cells. Activation of p75 or trkA receptors made either acetyl-CoA or cholinergic metabolism more susceptible to neurotoxic influences, respectively. Neurotoxins aggravated detrimental effects of each other, particularly in differentiated cells. Thus brain cholinergic neurons might display a differential susceptibility to Al and other neurotoxins depending on their genotype or phenotype-dependent variability of the cholinergic and acetyl-CoA metabolism.

Angiogenesis effects of nerve growth factor (NGF) on rat corneas

This study was performed to evaluate the effects of nerve growth factor (NGF) upon angiogenesis in the rat cornea, to examine its possible application as an alternative angiogenic inducer and to provide basic data for further studies. Angiogenesis was induced by cornea micropocket assay, as previously described. Eight of thirty two eyes of Sprague-Dawley rats were randomly assigned to one of four groups, namely, a non-NGF group (Group 0), a 0.5 ng of NGF group (Group 0.5), a 1.0 ng of NGF group (Group 1.0) and a 5.0 ng of NGF group (Group 5.0). Pellets made of poly-2-hydroxylethylmethacrylate and sucralfate were implanted into the corneal stroma no closer than 1 mm from the limbus. After the implantation, the number of new vessels, vessel length and circumferential neovascularization were examined daily under the surgical microscope over a period of 7 days. The area of neovascularization was determined using a mathematical formula. Although new vessels in Group 0 and Group 0.5 were first observed at day 5, those of Groups 1.0 and 5.0 were first noted on days 4 and 3, respectively. However, the growth rates of new vessels in Groups 1.0 and 5.0 were higher than those of Groups 0 and 0.5 with the passage of time. The number, length, circumferential neovascularization and areas covered by the vessels in Groups 1.0 and 5.0 were significantly more than in Group 0 and Group 0.5 (p<0.05). This study showed that NGF had a dose-dependent angiogenic effects on the rat cornea and that the minimal effective dose of NGF was 1.0 ng per cornea. Also, it showed that NGF would be useful in angiogenic studies as an alternative angiogenic inducer.

Neurotoxicity as a mechanism for neurodegenerative disorders: basic and clinical aspects

This three day meeting focused on chronic neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD), and amylotrophic lateral sclerosis (ALS). It attracted 69 participants from 10 countries with dominance of Chile and USA. Neurodegeneration and its prevention increasingly gain in importance as the number of people affected increases year-by-year. The meeting addressed various basic aspects having pragmatic implications such as: oxidative stress, inflammatory reaction, glial activation, role of glutamatergic system and apoptosis using a plethora of in vitro and in vivo methods.

Recombinant human nerve growth factor for clinical trials: protein expression, purification, stability and characterisation of binding to infusion pumps

Nerve growth factor (NGF) has been suggested to be of therapeutic benefit to patients with Alzheimer's disease. One of the early changes in this disease is a loss of cholinergic function within the brain, and NGF is able to rescue cholinergic neurons both in vitro and in vivo. We describe the production of recombinant human beta-NGF (rhNGF), using baculovirus infection of insect cells; its purification, formulation and subsequent stability for use in clinical trials. Tests were also carried out to monitor release of protein from infusion pumps and catheters for intracerebroventricular administration (icv). Initial problems with non-specific binding were overcome using a blocking formula.