J-2156, a small molecule somatostatin type 4 receptor agonist, alleviated hindpaw hypersensitivity in the streptozotocin-induced rat model of painful diabetic neuropathy but with a 2-fold decrease in potency at an advanced stage in the model, mimicking morphine.

There is a large unmet need for novel pain-killers to improve relief of painful diabetic neuropathy (PDN). Herein, we assessed the efficacy of the somatostatin type 4 (SST4) receptor agonist, J-2156, for relief of PDN in rats. Diabetes was induced with streptozotocin (STZ; 70 mg/kg) and bilateral hindpaw hypersensitivity was fully developed by 8-week post-STZ. In the intervals, 8-12-weeks (morphine-sensitive phase; Phase 1) and 16-18-weeks (morphine-hyposensitive phase; Phase 2) post-STZ, rats received a single dose of intraperitoneal (i.p.) J-2156 (10, 20, 30 mg/kg), gabapentin (100 mg/kg i.p.), subcutaneous morphine (1 mg/kg) or vehicle. Hindpaw withdrawal thresholds (PWTs) were assessed using von Frey filaments pre-dose and at regular intervals over 3-h post-dose. In Phase 1, J-2156 at 30 mg/kg evoked significant anti-allodynia in the hindpaws with maximal effect at 1.5 h compared with 1 h for gabapentin and morphine. The durations of action for all three compounds were greater than 3 h. The corresponding mean (±SEM) extent and duration of anti-allodynia (ΔPWT AUC) for gabapentin did not differ significantly from that for J-2156 (30 mg/kg) or morphine. However, in Phase 2, the ΔPWT AUC for morphine was reduced to approximately 25% of that in Phase 1, mirroring our previous work. Similarly, the mean (±SEM) ΔPWT AUC for J-2156 (30 mg/kg) in Phase 2 was approximately 45% of that for Phase 1 whereas for gabapentin the mean (±SEM) ΔPWT AUCs did not differ significantly (p > 0.05) between the two phases. Our findings further describe the preclinical pain relief profile of J-2156 and complement previous work in rat models of inflammatory pain, neuropathic pain and low back pain. SST4 receptor agonists hold promise as novel therapeutics for the relief of PDN, a type of peripheral neuropathic pain that is often intractable to relief with clinically used drug treatment options.

Deficits in spontaneous burrowing behavior in the rat bilateral monosodium iodoacetate model of osteoarthritis: an objective measure of pain-related behavior and analgesic efficacy.

OBJECTIVE: To characterize deficits in burrowing behavior - an ethologically-relevant rodent behavior - in the monosodium iodoacetate (MIA) rat model of osteoarthritis (OA), and the sensitivity of these deficits to reversal by analgesic drugs of both prototypical and novel mechanisms of action. A second objective was to compare the burrowing assay to a spontaneous locomotor activity (sLA) assay. METHOD: Male Wistar Han rats (200-220 g) received intrarticular (i.a.) injections of MIA or saline for sham animals. A deficit in the amount of sand burrowed from steel tubes filled with 2.5 kg of sand was used as a measure of pain-related behavior, and sensitivity to reversal of these deficits by analgesic drugs was assessed in bilaterally MIA-injected rats. RESULTS: Bilateral MIA injections induced a significant impairment of burrowing behavior, which was concentration-dependent. The temporal pattern of the deficits was biphasic: a large deficit at 3 days post-injection, resolving by day 14 and returning at the 21 and 28 day time points. At the 3 day time point ibuprofen, celecoxib and an anti-nerve growth factor (NGF) monoclonal antibody (mAb) were able to significantly reinstate burrowing behavior, whereas the fatty acid amide hydrolase (FAAH) inhibitor PF-04457845 and morphine displayed no reversal effect. Morphine impaired burrowing behavior at 3 mg/kg in sham animals. Deficits in rearing frequency in the locomotor activity assay proved irreversible by analgesics. CONCLUSION: Burrowing behavior provides an objective, non-reflexive read-out for pain-related behavior in the MIA model that has predictive validity in detecting analgesic efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) and an anti-NGF mAb.

Horizontal structure of acoustic intensity fluctuations in the ocean.

In April 1989 an acoustic experiment was carried out over the abyssal plain south of Madeira in which transmissions were made, for about an hour, at 482, 680, and 740 Hz from a ship steaming at 5 Kn to a receiving array towed by another ship 65 km away traveling on a parallel course at the same speed. The signals arrived by two paths, an upper path trapped in the surface duct and a lower path via the main sound channel. This paper describes the experiment and analyses of the intensity fluctuations in the signal received by the lower path. This allows the authors to investigate the horizontal structure of acoustic intensity fluctuations in the ocean when these are due principally to internal waves. This aspect of such acoustic intensity fluctuations has received little attention until now. The experimental results are compared with theoretical predictions based on the parabolic moment equations for propagation and scattering in randomly irregular media, and on the standard Garrett-Munk model for ocean internal waves. The experimental results and theoretical predictions agree quite well but the comparison also raises some new questions, in particular, about the correlation of intensity fluctuations as the acoustic transmission frequency is varied.

Melanocortin-4 receptor activation stimulates hypothalamic brain-derived neurotrophic factor release to regulate food intake, body temperature and cardiovascular function.

In the present study, we aimed to investigate the neuromodulatory role played by hypothalamic brain-derived neurotrophic factor (BDNF) in the regulation of acute cardiovascular and feeding responses to melanocortin-4 receptor (MC4R) activation. In vitro, a selective MC4R agonist, MK1, stimulated BDNF release from isolated rat hypothalami and this effect was blocked by preincubation with the MC3/4R antagonist SHU-9119. In vivo, peripheral administration of MK1 decreased food intake in rats and this effect was blocked by pretreatment with an anti-BDNF antibody administered into the third ventricle. When anorexia was induced with the cannabinoid-1 receptor (CB1R) antagonist AM251, the anti-BDNF antibody did not prevent the reduction in food intake. Peripheral administration of MK1 also increased mean arterial pressure, heart rate and body temperature. These effects were prevented by pretreatment with the anti-BDNF antibody whereas the intracerebroventricular administration of BDNF caused changes similar to those of MK1. These findings demonstrate for the first time that activation of MC4R leads to an acute release of BDNF in the hypothalamus. This release is a prerequisite for MC4R-induced effects on appetite, body temperature and cardiovascular function. By contrast, CB1R antagonist-mediated anorexia is independent of the MC4R/BDNF pathway. Overall, these results show that BDNF is an important downstream mediator of the MC4R pathway.

Pharmacotherapy of obesity.

Obesity has become a significant health problem in industrialised and developing countries, and despite all nutritional and behavioural approaches, its prevalence is still increasing. In recent years, the identification and characterisation of central and peripheral mechanisms involved in the regulation of energy balance has made remarkable progress and provided numerous targets for novel anti-obesity agents. However, only few anti-obesity drugs are on the market and not many compounds have entered clinical development. In the present review, the clinically available agents are discussed and their pharmacological profiles are compared. Some of the drugs that are currently in clinical development are mentioned as examples of the possible future range of anti-obesity agents. Selected topics in drug discovery are presented to illustrate novel targets and concepts for the pharmacotherapy of obesity.

Orphanin FQ-induced hyperphagia is mediated by corticosterone and central glucocorticoid receptors.

Orphanin FQ (Nociceptin) has been reported to stimulate food intake in satiated rats and to stimulate corticosterone release. A large body of evidence exists to link central feeding systems with the regulation of corticosterone. In this study, we sought to determine whether or not circulating corticosterone is necessary for the induction of food intake by Orphanin FQ. We found that intracerebroventricular injection of Orphanin FQ (0.64-5 nmoles) dose dependently stimulated food intake and plasma corticosterone within 30 min of injection. Removal of corticosterone, by adrenalectomy, abolished the hyperphagic effect of Orphanin FQ. The stimulatory effect of Orphanin FQ on food intake was still negated following a low dose of corticosterone replacement (corresponding to a plasma corticosterone concentration of 1.86+/-0.99 microg/dl). However, following a larger dose of corticosterone replacement (corresponding to a plasma corticosterone concentration of 8.92+/-0.55 microg/dl) the feeding effect was fully restored. We concluded this study by testing the glucocorticoid receptor antagonist, RU486 (Mifepristone, 80 microg/2 microl) on Orphanin FQ-induced feeding. Central injection of RU486, 30 min prior to injection of Orphanin FQ, significantly reduced Orphanin FQ-induced food intake in comparison to vehicle-treated controls. Overall, these data demonstrate the necessity for circulating corticosterone in the mediation of Orphanin-FQ-induced feeding and suggest that the mechanism through which the hyperphagic effect is obtained involves activation of central glucocorticoid receptors.

Time course of short-term and long-term orexigenic effects of Agouti-related protein (86-132).

Agouti-related protein (AGRP) is a newly identified orexigenic peptide that acts as an endogenous antagonist of melanocortin receptors MC3 and MC4. The present study examined the time course of the orexigenic effects of synthetic AGRP (86-132). Intracerebroventricular infusion of 0.1 nmol AGRP (86-132) increased food intake by 450 +/- 81% at 2 h post-injection. A second increase in non-cumulative food intake (512 +/- 135%) was observed at 6 h post-injection. Following a single dose of AGRP (86-132) (0.1 nmol) the increased food intake was sustained for 6 days, occurring in the light cycle of the first 2 days and subsequently switching to the dark cycle of the last 4 days. These time course profiles indicate the complexity of the mechanisms involved in AGRP-induced feeding.

Pharmacological studies on the "orphan" opioid receptor in central and peripheral sites.

We have exploited the availability of the "orphan" opioid receptor (referred to here as ORL1) in its "natural state" to investigate the effect of nociceptin (orphanin FQ), the endogenous agonist for the ORL1 receptor in the brain, vas deferens, and myenteric plexus of the small intestine. Nociceptin was a potent agonist in electrically stimulated preparations of vasa deferentia (rat and rabbit) and myenteric plexus (guinea-pig) (IC50 ranging from 18 to 31 nM) and susceptible to enzymic cleavage as addition of a cocktail of peptidase inhibitors to the organ bath produced a leftward shift in concentration-response curves (IC50 ranging from 2.1 to 4.9 nM). In radioligand binding experiments using brain membranes from rat, rabbit, and guinea-pig, [3H]nociceptin bound a single population of binding sites with high affinity (KD values ranging from 0.049 to 0.124 nM) and capacity (Bmax ranging from 143 to 254 fmol.mg-1 protein). However, the response to nociceptin in functional studies and in radioligand binding inhibitory assays was resistant to antagonism/displacement by naloxone and a range of other opioid receptor antagonists, thus displaying a very different pharmacological profile from that of the "classical" opioids. Therefore, we conclude that the effect of nociceptin in these studies is not via an action at mu, delta, or kappa opioid receptors but rather at an orphan opioid receptor, ORL1.

Nociceptin hyperpolarises neurones in the rat ventromedial hypothalamus.

Patch-clamp recording techniques were used to examine the effect of nociceptin upon neurones contained in slices from the rat ventromedial hypothalamus (VMH). Bath application of 50-300 nM nociceptin hyperpolarised neurones in a concentration-dependent manner that was not affected by either tetrodotoxin (TTX) or naloxone. In voltage-clamp studies nociceptin induced an outward current at -60mV that had a reversal potential of -100.2 +/- 4.6 mV and was abolished by bath application of 2 mM BaCl2.

Quantitative evaluation of Al maltolate-induced neurodegeneration with subsequent Al removal by desferrioxamine treatment.

The intracisternal administration of aluminum maltolate to New Zealand white rabbits produces a reproducible neurofibrillary degeneration which is significantly reversed by desferrioxamine treatment. Quantitative analysis of brain and spinal cord tissue demonstrates that the aluminum deposition is higher close to the injection site than at locations further removed from the point of administration. Most importantly, treatment with desferrioxamine removes most of the aluminum from the brain and spinal cord, even from the sites of highest concentration. The ability to manipulate this system in the formation and degradation of NFD and in removal of aluminum may shed light on mechanisms of NFD formation and have implications for therapeutic advances in the treatment of certain human neurodegenerative diseases.

Critical appraisal of two methods for determining aluminum in blood samples.

We report two methods for determining aluminum concentrations in blood. Method 1, proposed for routine monitoring of patients with chronic renal failure, includes a collection procedure that can be adopted by any renal dialysis unit, with a minimum of sample contamination. Plasma samples are diluted fourfold with HNO3/Triton X-100 matrix modifier. Method 2 is proposed for determining aluminum concentrations in patients with normal renal function, e.g., in drug studies and environmental monitoring. Samples are diluted with an equal volume of Mg(NO3)2 matrix modifier and atomized from a L'vov platform. By either method, analytical recovery of aluminum added to serum ranged between 92% and 105% throughout the linear calibration range. The reference interval (mean +/- SD) for aluminum in 22 healthy subjects by method 2 was 0.044 +/- 0.030 mumol/L.

Micro-quantity tissue digestion for metal measurements by use of a microwave acid-digestion bomb.

We describe a simple and convenient method for processing small amounts of tissue samples for trace-metal measurements by atomic absorption spectrometry, by use of a modified Parr microwave digestion bomb. Digestion proceeds rapidly (less than or equal to 90 s) in a sealed Teflon-lined vessel that eliminates contamination or loss from volatilization. Small quantities of tissue (5-100 mg dry weight) are digested in high-purity nitric acid, yielding concentrations of analyte that can be measured directly without further sample manipulation. We analyzed National Institute of Standards and Technology bovine liver Standard Reference Material to verify the accuracy of the technique. We assessed the applicability of the technique to analysis for aluminum in bone by comparison with a dry ashing procedure.

Measurement of lipid peroxidation products in rabbit brain and organs (response to aluminum exposure).

A method was developed for measuring the concentration of lipid peroxidation products in rabbit brain, heart, lung, liver, and kidney tissue. Specimens were homogenized in cold buffer, acidified, and heated to near boiling in the presence of thiobarbituric acid in order to form the malondialdehyde-thiobarbiturate adduct. After centrifugation, the supernatant was injected onto a reversed-phase high pressure liquid chromatography (HPLC) column, and the effluent was monitored for absorbance at 532 nm. Absorbances were compared to a standard curve constructed from absorbance data for tetraethoxypropane standards, which yield stoichiometric amounts of the malondialdehyde-thiobarbiturate adduct. Results were expressed as nmol of adduct per gram (dry weight) of tissue. Hippocampus had significantly greater concentrations of lipid peroxidation products (79.0 +/- 15.7 nmol per g) than did brainstem (52.1 +/- 13.8 nmol per g), but there was no significant increase in lipid peroxidation in aluminum treated rabbit brains when compared with controls. Aluminum intoxication appeared, however, to stimulate lipid peroxidation in heart, lung, liver, and kidney. Aluminum accumulation in brain and organ tissue of treated rabbits was confirmed by atomic absorption spectrophotometry of an acid digest of the homogenate. These results are in contrast to previous studies which demonstrated an increase in lipid peroxidation products in rat brains following oral administration of aluminum hydroxide.

An unusual lightning flash at kennedy space center.

A lightning flash that struck the 150-meter weather tower at Kennedy Space Center was studied by several research groups using varioul techniques. The flash had unusually large peak currents and a stepped leader of relatively short duration. The charged regions neutralized by the three return strokes were located within a horizontal layer between heights of about 6 and 8 kilometers, where environmental temperatures were about -10 degrees to -20 degrees C. The charge source for the first return stroke coincided with a vertical shaft of precipitation inferred to have been graupel or hail. Charge sources for subsequent strokes were near the edge of the detectable precipitation echo. The overall channel length was about 10 kilometers. A Vertically oriented intracloud discharge occurred after the three return strokes.

The influence of secondary depth cues on the understanding by Nigerian schoolboys of spatial relationships in pictures.

The ability of 105 Nigerian schoolboys to interpret pictures three-dimensionally was studied as a function of changing the number of depth cues on moving from monochrome photographs incorporating the effects of shadow, through fully cued line drawings, to line drawings containing only elevation cues. The experiment also investigated the effects of different amounts of previous formal training in technical drawing on performance in these tasks. The results showed a significant increase in performance as the number of depth cues increased above that contained in the minimum cued line drawings. However, the difference between the effects of fully cued line drawings and the photographs was not significant. Neither the main nor interaction effects relating to levels of formal training in technical drawing were significant.

Cardiovascular changes in labour associated with extradural analgesia using bupivacaine.

Cardiovascular changes were monitored continuously in 13 women during stimulated labour conducted under extradural analgesia with bupivacaine. Three solutions of bupivacaine (0.5% plain, 0.25% with adrenaline and 0.5% with adrenaline) were administered in a random fashion. The results show that the plain solution of bupivacaine was associated with a decrease in central venous pressure and an increase in maternal heart rate which approached statistical significance 40-45 min after administration. These changes did not occur when solutions containing adrenaline were used. The small number of patients and the random administration of the bupivacaine solutions make it difficult to establish the exact significance of the cardiovascular changes observed and a further within-patient study is required.

Cardiovascular effects of extradural analgesia in labour: comparison of bupivacaine with lignocaine.

Two groups of patients who requested extradural analgesia were studied in a within-patient controlled trial and received either 0.5% bupivacaine with adrenaline 5 mug/ml or 0.5% bupivacaine plain as the analgesic agent (first group) or 0.5% bupivacaine or 2% lignocaine both with adrenaline 5 mug/ml (second group). Arterial pressure, central venous pressure (CVP), maternal and foetal heart rate and uterine contractions were monitored continuously. There was no significant difference in any of the cardiovascular measurements when solutions of 0.5% bupivacaine (with or without adrenaline 5 mug/ml) were used. The second group had a statistically significant increase in CVP during the study period in which 2% lignocaine was used. The position of the patient did not affect the cardiovascular measurements in either group. Since the addition of adrenaline 5 mug/ml to bupivacaine solutions did not confer any apparent advantages, it is concluded that plain solutions of 0.5% bupivacaine should be used except in the longest labours.