Oral absorption of sodium pentobarbital and effects on gastrointestinal function

Role of cAMP/pCREB and GSK-3β/NF-κB p65 signaling pathways in the renoprotective effect of mirabegron against renal ischemia-reperfusion injury in rats

Acute kidney injury and other renal disorders are thought to be primarily caused by renal ischemia-reperfusion (RIR). Cyclic adenosine monophosphate (cAMP) has plenty of physiological pleiotropic effects and preserves tissue integrity and functions. This research aimed to examine the potential protective effects of the β3-adrenergic receptors agonist mirabegron in a rat model of RIR and its underlying mechanisms. Male rats enrolled in this work were given an oral dose of 30 mg/kg mirabegron for two days before surgical induction of RIR. Renal levels of kidney injury molecule-1 (KIM-1), monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), Interleukin-10 (IL-10), cAMP, cAMP-responsive element binding protein (pCREB), and glycogen synthase kinase-3 beta (GSK-3β) were assessed along with blood urea nitrogen and serum creatinine. Additionally, caspase-3 and nuclear factor-kappa B (NF-κB) p65 were explored by immunohistochemical analysis. Renal specimens were inspected for histopathological changes. RIR led to renal tissue damage with elevated blood urea nitrogen and serum creatinine levels. The renal KIM-1, MCP-1, TNF-α, and GSK-3β were significantly increased, while IL-10, cAMP, and pCREB levels were reduced. Moreover, upregulation of caspase-3 and NF-κB p65 protein expression was seen in RIR rats. Mirabegron significantly reduced kidney dysfunction, histological abnormalities, inflammation, and apoptosis in the rat renal tissues. Mechanistically, mirabegron mediated these effects via modulation of cAMP/pCREB and GSK-3β/NF-κB p65 signaling pathways. Mirabegron administration could protect renal tissue and maintain renal function against RIR.

Effects of pentobarbital anesthesia on nociceptive processing in the medial and lateral pain pathways in rats

OBJECTIVE

To investigate the effects of pentobarbital anesthesia on nociceptive processing in the medial and lateral pain pathways.

METHODS

Laser stimulation was employed to evoke nociceptive responses in rats under awake or anesthetic conditions. Pain-related neuronal activities were simultaneously recorded from the primary somatosensory cortex (SI), ventral posterolateral thalamus (VPL), anterior cingulate cortex (ACC), and medial dorsal thalamus (MD) with 4 eight-wire microelectrode arrays.

RESULTS

Compared with the awake state, pentobarbital anesthesia significantly suppressed the neural activities induced by noxious laser stimulation. Meanwhile, the pain-evoked changes in the neuronal correlations between cortex and thalamus were suppressed in both medial and lateral pain pathways. In addition, the spontaneous firing rates in all the 4 areas were altered (including inhibition and excitation) under the condition of anesthesia.

CONCLUSION

The nociceptive processing in the brain can be dramatically changed by anesthesia, which indicates that there are considerable differences in the brain activities between awake and anesthetized states. It is better to employ awake animals for recording neural activity when investigating the sensory coding mechanisms, especially pain coding, in order to obtain data that precisely reflect the physiological state.

Sodium pentobarbital anesthesia transiently enhances the severity of infection following intragastric, but not intravenous, inoculation of Listeria monocytogenes in mice

In the present study we observed that mice anesthetized with sodium pentobarbital were far more susceptible to gastrointestinal challenge with Listeria monocytogenes than were unanaesthetized mice. The effect of pentobarbital anesthesia was transient (gone within 2 h) and did not alter the severity of infection following i.v. challenge with L. monocytogenes. Treatment with pharmacological inhibitors of gastric acidity (i.e. cimetidine and omeprazole), or intestinal motility (loperamide), did not duplicate the effect of pentobarbital on gastrointestinal listeriosis. These findings suggest that sodium pentobarbital anesthesia causes a short-lived but striking diminution in resistance to gastrointestinal listeriosis in mice, via an undefined mechanism.

Comparison of oral pentobarbital sodium (nembutal) and oral chloral hydrate for sedation of infants during radiologic imaging: preliminary results

OBJECTIVE

The purpose of this study was to compare the safety and efficacy of oral cherry-flavored pentobarbital sodium (Nembutal) and oral chloral hydrate to sedate infants undergoing radiologic imaging.

SUBJECTS AND METHODS

We prospectively recorded data for all infants sedated with oral cherry-flavored pentobarbital sodium and oral chloral hydrate for imaging examinations between January 1997 and August 1999. The parameters recorded were each patient's age, weight, and American Society of Anesthesiologists classification; the time required to sedate; the total length of sedation time; the time required to discharge from the recovery room; and adverse events. The two-sample Student's t test and Fisher's exact test were used for statistical analysis.

RESULTS

Oral pentobarbital sodium was administered to 317 infants. These infants had a mean age +/- SD of 6.9 +/- 3.1 months and a mean weight of 7.8 +/- 4.8 kg; they received a median dose of 4 mg/kg of body weight. Oral chloral hydrate was administered to 358 infants. These infants had a mean age of 5.9 +/- 3.3 months and a mean weight of 7.3 +/- 4.9 kg; they received a median dose of 50 mg/kg of body weight. The mean time required to sedate was 19 +/- 14 min for infants receiving oral pentobarbital sodium and 16 +/- 11 min for infants receiving oral chloral hydrate (p = 0.02); the mean time required to discharge was 100 +/- 35 min for infants in the oral pentobarbital sodium group and 103 +/- 36 min for infants in the oral chloral hydrate group (p = 0.31); the mean length of sedation was 81 +/- 34 min for the oral pentobarbital sodium group and 86 +/- 36 min for the oral chloral hydrate group (p = 0.07); and median American Society of Anesthesiologists classification for both groups was P1. Oral pentobarbital sodium was inadequate for sedation in one patient (0.3%) and chloral hydrate was inadequate for sedation in another (0.3%) (p = 1.00). Adverse events were recorded for five patients (1.6%) in the oral pentobarbital sodium group and for six patients (1.7%) in the chloral hydrate group (p = 0.99).

CONCLUSION

Oral pentobarbital sodium is as safe and efficacious as oral chloral hydrate for sedating infants.

GABA(A) receptors on calbindin-immunoreactive myenteric neurons of guinea pig intestine

These studies were carried out to characterize the properties of gamma-aminobutyric acidA (GABA(A)) receptors on guinea pig intestinal myenteric neurons maintained in primary culture. In addition, the type of neuron expressing GABA(A) receptors was identified using immunohistochemical methods. Whole-cell patch clamp recordings of currents elicited by GABA and acetylcholine (ACh) were obtained using pipettes containing Neurobiotin. After electrophysiological studies, neurons were processed for localization of calbindin-D28K-immunoreactivity (calbindin-ir). GABA (1 mM) and ACh (3 mM) caused inward currents in most cells tested. GABA currents were mimicked by muscimol (1-300 microM) and were blocked by bicuculline (10 microM) indicating that GABA was acting at GABA(A) receptors. GABA currents were associated with a conductance increase and a linear current/voltage relationship with a reversal potential of 1 +/- 1 mV (n = 5). Pentobarbital (PB, 3-1000 microM) and diazepam (DZP, 0.01-10 microM) potentiated GABA-induced currents. A maximum concentration of DZP (1 microM) increased GABA-induced currents 3.1 +/- 0.3 times while PB (1000 microM) increased GABA currents by 11 +/- 2 times. In outside-out patches, the amplitude of GABA-activated single-channel currents was linearly related to membrane potential with a single-channel conductance of 28.5 + 0.5 pS (n = 10). PB and DZP increased the open probability of GABA-induced single-channel currents. Neurons containing calbindin-ir were large, were isolated from other neurons and had GABA current amplitudes of -3.4 +/- 0.3 nA (n = 48). Neurons with weak or absent calbindin-ir were smaller, were localized in clusters of cells and had GABA-induced current amplitudes of -0.6 +/- 0.1 nA (n = 20). ACh-induced currents were smaller in calbindin-ir neurons (-0.7 +/- 0.1 nA) compared to weakly calbindin-ir neurons (-1.4 +/- 0.1 nA). These results indicate that myenteric calbindin-ir neurons express a high density of GABA(A) receptors. Cell size and location allow visual identification of neurons likely to contain calbindin-ir permitting targeted studies of the properties of these neurons.

Effect of dosing volume on gastrointestinal absorption in rats: analysis of the gastrointestinal disposition of L-glucose and estimation of in vivo intestinal membrane permeability

The effect of the oral dosing volume (DV) on both gastric emptying and intestinal absorption was examined by analyzing the gastrointestinal disposition of a model solute, L-glucose, in rats. The amount of 14C-labeled L-glucose in the gastric and intestinal contents of sacrificed rats was measured at various times after administration, and the data were analyzed with a linear model, assuming first-order gastric emptying followed by first-order intestinal absorption. The gastric emptying rate constant (kg) rose from 0.025 to 0.072 min-1 by increasing DV from 0.1 to 3 mL/rat, whereas the intestinal absorption rate constant (ka) decreased from 0.031 to 0.015 min-1. This decrease in ka was attributed to an increase in the average intestinal lumen volume (Vav) from 24 to 39 microL/cm, assuming that the relationship ka = CLa,app/Vav holds (where CLa,app is the apparent intestinal membrane permeability clearance or the product of the apparent membrane permeability coefficient and surface area). The CLa,app (= kaVav), a measure of the in vivo intestinal membrane permeability, was 0.74 microL/cm/min for a DV value of 0.1 mL/rat and decreased only marginally by 20% for larger values of DV, suggesting an insignificant effect of DV on CLa,app. These results suggest that the accelerating effect of the increased kg, produced by the increased DV on the gastrointestinal absorption, may be canceled by the decrease in ka. A decrease in ka may lead to a decrease in the fraction absorbed. Finally, this study also provides a means for carrying out physiological modeling of drug absorption following oral administration.