Involvement of imidazoline and opioid receptors in the enhancement of clonidine-induced analgesia by sulfisoxazole.

Clonidine, an alpha2-adrenergic agonist, has been demonstrated to produce significant analgesia and potentiate morphine analgesia. Endothelin (ETA) receptor antagonists have also been found to potentiate the antinociceptive response to morphine. Clonidine and ET have been reported to have cardiovascular interactions involving the sympathetic nervous system, but it is not known whether ETA receptor antagonist affects clonidine analgesia. This study examined the influence of sulfisoxazole (ETA receptor antagonist) on clonidine analgesia. Male Swiss Webster mice were used to determine antinociceptive response of drugs by measuring tail-flick latency. The effect of clonidine (0.3, 1.0, and 3.0 mg/kg, i.p.) alone or in combination with sulfisoxazole (25, 75, and 225 mg/kg, p.o.) on analgesia and body temperature was determined. Clonidine produced a dose-dependent analgesia and hypothermia. Sulfisoxazole (25, 75, and 225 mg/kg), when administered with clonidine (0.3 mg/kg), significantly potentiated (31% increase in area under the curve (AUC)) the analgesic effect of clonidine. Yohimbine (alpha2-adrenergic receptor antagonist) did not affect analgesic effect of clonidine plus sulfisoxazole. Idazoxan (I1-imidazoline and alpha2-adrenergic receptor antagonist) reduced (47% decrease in AUC) the analgesic effect of clonidine plus sulfisoxazole. Treatment with naloxone reduced (46% decrease in AUC) the analgesic effect of clonidine plus sulfisoxazole. The effect of another ETA receptor antagonist, BMS-182874 (2, 10, and 50 microg, i.c.v.) was studied, and it was found that the dose of 10 microg significantly potentiated (26% increase in AUC) the analgesic effect of clonidine. These results indicate that sulfisoxazole, an ETA receptor antagonist, potentiates the analgesic effect of clonidine, which could be mediated through I1-imidazoline receptors and opioid receptors.

Role of endothelin (ETA) receptors in neonatal morphine withdrawal.

We have previously demonstrated role of central endothelin (ET) receptors in neonatal morphine tolerance. The present study was conducted to investigate involvement of central ET receptors in neonatal rat morphine withdrawal. The aim was to determine activation of G-proteins coupled to opioid and ET receptors by morphine and ET ligands in neonatal rat brains during morphine withdrawal. Pregnant female rats were rendered tolerant to morphine by chronic exposure to morphine pellets over 7 days. Withdrawal was induced on day 8 by removal of pellets. Rat pups were delivered by cesarean section 24 h after pellet removal. G-protein stimulation induced by morphine; ET-1; ETA receptor antagonist, BMS182874; and ETB receptor agonist, IRL1620, was determined in the brain of neonatal rats undergoing morphine withdrawal by [35S]GTPgammaS binding assay. Morphine-induced maximal stimulation of G-protein in morphine withdrawal group (83.60%) was significantly higher compared to placebo control group (66.81%). EC50 value for ET-1-induced G-protein stimulation during morphine withdrawal (170.60 nM) was higher than control (62.5 nM). BMS182874, did not stimulate GTP binding in control but significantly increased maximal stimulation of G-proteins in morphine withdrawal (86.07%, EC50 = 31.25 nM). IRL1620-induced stimulation of G-proteins was similar in control and morphine withdrawal. The present findings indicate involvement of central ETA receptors in neonatal morphine withdrawal.

Involvement of central endothelin receptors in neonatal morphine withdrawal.

The involvement of central endothelin (ET) receptors in neonatal morphine tolerance has been demonstrated. The present study investigates the role of central ET receptors in morphine withdrawal in neonatal rats. The aim was to determine whether activation of G-proteins coupled to opioid and ET receptors by morphine and various ET receptor modulators is affected during morphine withdrawal in neonatal rats. Pregnant female rats were rendered tolerant to morphine by chronic exposure to morphine pellets during 7 days. On Day 8, pellets were removed and rats were allowed to undergo withdrawal for 24 hrs. Rat pups were delivered by cesarean section. G-protein stimulation induced by morphine; ET-1; the ET(A) receptor antagonist, BMS182874; and the ET(B) receptor agonist, IRL1620, were determined in the brain of neonatal rats undergoing morphine withdrawal by [35S]GTPgammaS binding assay. Morphine produced higher (P < 0.05) maximal stimulation of G-protein in the morphine-withdrawal group (83.60%) compared with the placebo group (66.81%). ET-1-induced G-protein stimulation was also altered, and the median effective concentration (EC50) during morphine withdrawal (170.60 nM) was significantly higher than placebo (62.5 nM; P< 0.05). The maximal stimulation induced by the ET(A) receptor antagonist, BMS182874, in the morphine-withdrawal group (86.07%; EC50 = 31.25 nM) was significantly higher than in the placebo group (EC50 > 1000 nM). The ET(B) agonist, IRL1620, induced G-protein stimulation was similar in placebo (73.43%, EC50 = 13.26 nM) and morphine-withdrawal groups (75.08%, EC(50) = 11.70 nM), respectively. To our knowledge, this is the first report indicating involvement of central ET(A) receptors in neonatal morphine withdrawal.

Procalcitonin as a screening test for late-onset sepsis in preterm very low birth weight infants.

OBJECTIVE: To compare the utility of procalcitonin (PCT) vs C-reactive protein (CRP) as indicators of late-onset neonatal sepsis in very low birth weight (VLBW) infants. METHODS: PCT and CRP levels were measured in VLBW infants with suspected sepsis and controls. Comparisons were made between infected vs noninfected infants. Using cutoff values of 0.5 and 1.0 ng/ml for PCT and 0.8 mg/dl for CRP, sensitivity, specificity, positive and negative predictive values were calculated to evaluate these assays as potential predictors of late-onset sepsis. RESULTS: A total of 67 infants were evaluated. Mean PCT levels were significantly higher in the infected group (5.41 ng/ml) compared to the noninfected group (0.43 ng/ml) (p < 0.001). At a cut off value of 0.5 ng/ml, the sensitivity of PCT was 97%, whereas that of CRP was 73% in predicting late-onset sepsis. At a PCT cutoff of 1.0 ng/ml, sensitivities of PCT and CRP were similar (72% each). CONCLUSION: PCT (0.5 ng/ml) is more sensitive than CRP in predicting late-onset sepsis in VLBW infants.

Role of endothelin in neonatal morphine tolerance.

Management of neonatal opioid tolerance and withdrawal symptoms remains a major challenge in neonatal intensive care units. We provide evidence that central endothelin (ET) mechanisms are involved in the development of morphine tolerance in neonatal rats. Pregnant rats were rendered tolerant to morphine and rat pups were delivered by cesarean section. The effect of morphine tolerance on characteristics of ET receptors in neonatal rats was determined. The affinity (Kd) and density (Bmax) of [I]ET-1 binding in the brain was found to be similar in placebo and morphine-tolerant neonatal rats. Morphine and ET-1-induced G-protein stimulation was determined in placebo and morphine-tolerant neonatal rats by [S]GTPgammaS binding assay. Morphine produced significantly lower (P < 0.05) maximal stimulation in morphine-tolerant neonatal rats (33.10%) when compared with placebo-treated neonatal rats (90.90%). Maximal stimulation produced by ET-1 in morphine-tolerant neonatal rats (41.26%) was also significantly lower (P < 0.05) as compared with placebo-treated neonatal rats (92.23%). This is the first report indicating the involvement of ET in neonatal morphine tolerance as evidenced by attenuation of ET-1-induced stimulation of GTP binding in neonatal rats tolerant to morphine.

Upregulation of neutrophil surface adhesion molecules in infants of pre-eclamptic women.

OBJECTIVE: To evaluate evidence of neutrophil activation in infants born to pre-eclamptic women and examine any association between degree of neutrophil activation and severity of pre-eclampsia. DESIGN: This study utilized quantitative flow cytometry to determine whether the expression of surface adhesion molecules: CD18, CD11a, CD11b, and CD11c on cord blood neutrophils using mean channel fluorescence values (MCF). A total of 20 infants of pre-eclamptic women were compared with a control group of 19 infants of normotensive women. RESULTS: MCF values were significantly higher in infants born to pre-eclamptic women vs controls: CD18 (432.0+/-236.3 vs 230.5+/-97.9; p=0.002), CD11a (552.9+/-272.4 vs 326.9+/-268.6; p=0.003), CD11b (937.2+/-521.9 vs 576.6+/-352.9; p=0.025), and CD11c (228.5+/-130.3 vs 133.0+/-77.1; p=0.006), respectively. The mean MCF values appeared higher in severe vs mild pre-eclampsia. CONCLUSIONS: This study revealed neutrophil activation in infants born to pre-eclamptic women. The relationship between neutrophil activation and severity of pre-eclampsia warrants further study.

Ghrelin levels in cord blood from concordant and discordant twin pairs: association with birth weight and postnatal catch-up growth.

OBJECTIVE: To determine whether cord blood ghrelin levels in discordant and concordant twins predict postnatal catch-up growth. METHODS: After obtaining parental consent, cord blood samples were collected at delivery for total ghrelin analysis. Infant weight, length and head circumference were obtained at birth, 2, 4, and 6 months of age. Data points post-discharge were obtained from the pediatrician's office or via parent contact. Pearson correlation evaluated the relationship between cord blood ghrelin levels and postnatal catch-up growth. RESULTS: There was a statistically significant correlation between cord blood ghrelin levels and birth weight among concordant twins, but not among the discordant twins. Cord blood ghrelin levels did not predict postnatal growth at 6 months of age overall, but did so in the subset of monochorionic, discordant pairs. CONCLUSION: Cord blood ghrelin levels did not correlate overall with birth size or postnatal catch-up growth in concordant and discordant twin pairs, but did so in selected subsets. Further studies are needed.

Evidence that morphine tolerance may be regulated by endothelin in the neonatal rat.

BACKGROUND: Opioids are widely used in the neonatal intensive care units for analgesia and sedation. Management of tolerance and withdrawal symptoms in neonates remains a major challenge. OBJECTIVES: The present study investigates the involvement of a central endothelin (ET) mechanism in the development of tolerance to morphine in neonatal rats. METHODS: Pregnant female rats were rendered tolerant to morphine and rat pups were delivered at term by cesarean section. The affinity (Kd) and density (Bmax) of ET receptors was determined by [125I]ET-1 binding in the brains of neonatal rats. Changes in G-protein stimulation were determined in placebo and morphine-tolerant neonatal rats by [35S]-guanosine-5'-o-(3-thio)triphosphate ([35S]GTPgammaS)-binding assay. RESULTS: Morphine tolerance did not affect the characteristics (affinity and density) of the ET receptors in the neonatal rat brains. Morphine as well as ET-1 produced significantly lower (p < 0.05) maximal stimulation of [35S]GTPgammaS binding in morphine-tolerant neonatal rats compared to the placebo group. The ETA receptor antagonist, BMS182874, produced significantly higher stimulation of G proteins in the morphine-tolerant compared to the placebo group. The ETB receptor agonist, IRL1620, produced a similar effect in both placebo and morphine-tolerant rats. CONCLUSIONS: This is the first report indicating the involvement of the G-protein-coupled ETA receptor in neonatal morphine tolerance.