Association Between Tacrolimus Pharmacokinetics and Cytochrome P450 3A5 and Multidrug Resistance Protein 1 Exon 21 Polymorphisms.

BACKGROUND: Individual differences in the pharmacokinetics (PK) of tacrolimus (TAC), an immunosuppressive drug, are reportedly associated with single-nucleotide polymorphisms (SNPs) of cytochrome P450 (CYP) 3A5 and multidrug resistance protein 1 (MDR1). We determined the effect of SNPs in CYP3A5 and MDR1 exons 21 and 26 on TAC PK parameters. METHODS: Thirty-eight Japanese patients who underwent renal transplantation were genotyped for CYP3A5 and exons 21 and 26 of MDR1 with the use of polymerase chain reaction-restriction fragment length polymorphism analysis. TAC concentrations were determined 3 weeks after renal transplantation and PK parameters calculated. RESULTS: The area under the blood concentration-time curve (AUC) in CYP3A5 expressers was significantly higher than that in CYP3A5 nonexpressers (CYP3A5*3/*3). Patients with the MDR1 exon 21 A allele (G2677A) showed higher dose-adjusted AUC (AUC/D) and lower doses of TAC than those who did not possess that allele. Furthermore, patients with both CYP3A5*3/*3 and MDR1 G2677A showed significantly lower TAC doses and higher dose-adjusted trough levels (C/D) and AUC/D than those without those genotypes. There was no significant association between MDR1 exon 26 polymorphism and the PK of TAC. CONCLUSIONS: Patients with both CYP3A5*3/*3 and MDR1 G2677A had higher blood TAC concentrations than those without those genotypes. Japanese patients should be carefully monitored for consideration of lower TAC doses, because 24% of Japanese patients have double mutations.

A simplified chart for determining the initial loading dose of teicoplanin in critically ill patients.

AIM OF THE STUDY: A simplified chart to determine the initial loading dose of teicoplanin (TEIC chart) for achieving the target trough concentration was developed. The aim of the present study was to evaluate the usefulness of this chart in critically ill patients. PATIENTS AND METHODS: The initial loading dose and maintenance dose to achieve a target trough concentration ≥10 µg/mL on day 4 was determined using the teicoplanin TDM software and presented in a TEIC chart. The dosage of teicoplanin, including the loading dose for the first 2 days and the maintenance dose thereafter, was selected from the chart (chart method, N = 41) or calculated using TDM software (software method, N = 39). RESULTS: The performance rate of initial loading of teicoplanin increased from 83.0% to 100% after the TEIC chart was introduced (P = 0.016). The TEIC chart significantly reduced the time required for determining the initial loading dose compared with the use of software (1.9±0.6 min vs. 29.7±13.8 min, P < 0.001). No significant differences were observed in the rates of achieving a target level ≥10 µg/mL (P = 0.766). CONCLUSION: The TEIC chart enables a simple, rapid, and reliable determination of teicoplanin dosage.

Outcome measurement of extensive implementation of antimicrobial stewardship in patients receiving intravenous antibiotics in a Japanese university hospital.

BACKGROUND: Antimicrobial stewardship has not always prevailed in a wide variety of medical institutions in Japan. METHODS: The infection control team was involved in the review of individual use of antibiotics in all inpatients (6348 and 6507 patients/year during the first and second annual interventions, respectively) receiving intravenous antibiotics, according to the published guidelines, consultation with physicians before prescription of antimicrobial agents and organisation of education programme on infection control for all medical staff. The outcomes of extensive implementation of antimicrobial stewardship were evaluated from the standpoint of antimicrobial use density, treatment duration, duration of hospital stay, occurrence of antimicrobial-resistant bacteria and medical expenses. RESULTS: Prolonged use of antibiotics over 2 weeks was significantly reduced after active implementation of antimicrobial stewardship (2.9% vs. 5.2%, p < 0.001). Significant reduction in the antimicrobial consumption was observed in the second-generation cephalosporins (p = 0.03), carbapenems (p = 0.003), aminoglycosides (p < 0.001), leading to a reduction in the cost of antibiotics by 11.7%. The appearance of methicillin-resistant Staphylococcus aureus and the proportion of Serratia marcescens to Gram-negative bacteria decreased significantly from 47.6% to 39.5% (p = 0.026) and from 3.7% to 2.0% (p = 0.026), respectively. Moreover, the mean hospital stay was shortened by 2.9 days after active implementation of antimicrobial stewardship. CONCLUSION: Extensive implementation of antimicrobial stewardship led to a decrease in the inappropriate use of antibiotics, saving in medical expenses, reduction in the development of antimicrobial resistance and shortening of hospital stay.

Rifampicin attenuates the MPTP-induced neurotoxicity in mouse brain.

Rifampicin, an antibacterial drug, is highly effective in the treatment of tuberculosis and leprosy. Recently, it has been reported to have neuroprotective effects in in vitro and in vivo models. This study was designed to elucidate its neuroprotective effects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity (known as an in vivo mouse model of Parkinson's disease). Mice were injected intraperitoneally (i.p.) with MPTP (10 mg/kg) four times at 1-h intervals, and brains were analyzed 3 or 7 days later. Rifampicin at 20 mg/kg (i.p., twice) had protective effects against MPTP-induced neuronal damage (immunohistochemical changes in tyrosine hydroxylase) in both the substantia nigra and striatum. Rifampicin also protected against the MPTP-induced depletions of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) in the striatum. The maximal concentrations of rifampicin between 30 and 240 min after a single rifampicin injection (20 mg/kg, i.p.) were 2.6 microM (at 30 min) in plasma and 0.77 microM (at 60 min) in striatum. Next, the effects of rifampicin on oxidative stress [lipid peroxidation in mouse brain homogenates and free radical-scavenging activity against diphenyl-p-picrylhydrazyl (DPPH)] were evaluated to clarify the underlying mechanism. At 1 microM or more, rifampicin significantly inhibited both lipid peroxidation in the striatum and free radical production. These findings suggest that in mice, rifampicin can reach brain tissues at concentrations sufficient to attenuate MPTP-induced neurodegeneration in the nigrostriatal dopaminergic neuronal pathway, and that an inhibitory effect against oxidative stress may be partly responsible for its observed neuroprotective effects.

Induction of histamine release from rat peritoneal mast cells by histatins.

Human salivary histatins (Hsts), which belong to a salivary polypeptide family, have potent antifungal activity against Candida albicans and Cryptococcus neoformans, and are expected to be useful as therapeutic reagents against Candida species. However, little is known about the effect of Hsts on host immune systems. Thus we conducted a series of in vitro experiments with rat mast cells to determine whether histatin 5 (Hst 5) or histatin 8 (Hst 8) has a histamine-releasing effect on mast cells. Both Hst 5 and Hst 8 induced histamine release from rat peritoneal mast cells in a dose-dependent manner (10(-9) to 10(-5) M). Hst 5 had a stronger releasing effect than Hst 8. The histamine release induced by Hst 5 (10(-6) M) was increased by the presence of 0.5 mM Ca2+, but decreased by 2mM Ca2+. Alternatively, the histamine release induced by Hst 8 (10(-6) M) was inhibited by the presence of Ca2+ (0.5 to 2 mM). These results suggest that Hsts have limited usefulness as therapeutic agents due to induction of histamine release from mast cells.

Endotoxin impairs biliary transport of sparfloxacin and its glucuronide in rats.

The effect of endotoxin on glucuronidation and hepatobiliary transport of quinolone antimicrobial agents was investigated in rats using sparfloxacin and p-nitrophenyl glucuronide as model drugs. The biliary clearance experiments were performed 24 h after a single intraperitoneal injection of endotoxin (1 mg/kg). Endotoxin significantly delayed the disappearance of sparfloxacin from plasma and increased plasma concentration of its glucuronide after intravenous injection of sparfloxacin (10 mg/kg). Significant decreases in the systemic clearance of sparfloxacin and the biliary clearance of sparfloxacin and the glucuronide were observed. Endotoxin had no effect on in vitro glucuronidation activity using p-nitrophenol as a substrate. When p-nitrophenyl glucuronide (8 mg/kg) was administered in endotoxin-pretreated rats, significant decreases in the systemic clearance, biliary clearance and renal clearance of p-nitrophenyl glucuronide were observed. These findings suggest that endotoxin decreases the biliary excretion of sparfloxacin and its glucuronide probably due to impairment of their hepatobiliary transport systems and renal handling.

Differential effect of phosphodiesterase inhibitors on IL-13 release from peripheral blood mononuclear cells.

Increased cyclic AMP (cAMP)-phosphodiesterase (PDE) activity in peripheral blood leucocytes is associated with the immunological inflammation that characterizes allergic diseases, such as atopic dermatitis and allergic rhinitis. Recently, it has been found that IL-13 has similar biological functions to IL-4. The aim of this study was to investigate the possible involvement of cAMP-PDE activity on IL-13 release from peripheral blood mononuclears cells (PBMC) from atopic asthma patients. Phytohaemagglutinin (PHA)-induced IL-13 release from PBMC was concentration-dependently inhibited by rolipram, a type 4 PDE inhibitor, as well as by dibutyryl cAMP, a membrane-permeant cAMP analogue. However, theophylline, a non-specific PDE inhibitor, and cilostazol, a type 3 PDE inhibitor, failed to inhibit IL-13 release. The inhibitory effect of rolipram was enhanced by the addition of forskolin (10(-4) m), an adenylyl cyclase stimulator. PHA itself did not alter the intracellular cAMP level. Rolipram concentration-dependently increased cAMP level in PHA-stimulated PBMC, and this increase was synergistically facilitated by the addition of forskolin (10(-4) m). These results suggest that type 4 PDE inhibitors, alone or synergistically in combination with forskolin, inhibit PHA-induced IL-13 release from PBMC of atopic asthma patients by elevating intracellular cAMP concentrations. These inhibitors have the potential to exert an anti-inflammatory effect by inhibiting IL-13 production in allergic diseases such as atopic asthma.

Effect of endotoxin on P-glycoprotein-mediated biliary and renal excretion of rhodamine-123 in rats.

The effects of Klebsiella pneumoniae endotoxin on the biliary excretion and renal handling of rhodamine-123 were investigated in rats at different times after intraperitoneal injection (1 mg/kg of body weight). The typical substrates for P glycoprotein, i.e., cyclosporine, colchicine, and erythromycin, inhibited the biliary clearance of rhodamine-123, whereas a substrate for organic cation transporter, cimetidine, did not inhibit clearance, suggesting that rhodamine-123 is transported mainly by P glycoprotein. The biliary, renal, and tubular secretory clearances of rhodamine-123 and the glomerular filtration rate significantly decreased 6 h after injection of endotoxin but returned to control levels by 24 h. These results suggest that endotoxin-induced decreases in P-glycoprotein-mediated biliary excretion and renal handling of rhodamine-123 were probably due to impairment of P-glycoprotein-mediated transport ability. Pretreatment with pentoxifylline (50 mg/kg) significantly inhibited endotoxin-induced increases in tumor necrosis factor alpha (TNF-alpha) levels in plasma, which ameliorated the endotoxin-induced reduction of the biliary excretion of rhodamine-123. It is likely that endotoxin-induced impairment of the transport of rhodamine-123 is caused, in part, by overproduction of TNF-alpha. The effect of endotoxin on the expression of P-glycoprotein mRNA in liver and kidneys of rats was investigated by using a reverse transcriptase PCR. The expression of Mdr1a mRNA in both liver and kidney decreased 6 h after endotoxin injection and returned to control levels after 24 h, whereas the expression of Mdr1b mRNA in liver increased at both times and that in kidney decreased at 24 h. These findings suggest that K. pneumoniae endotoxin dramatically decreases P-glycoprotein-mediated biliary and renal excretion of rhodamine-123 probably by decreasing the expression of Mdr1a, which is likely due to increased plasma TNF-alpha levels.

Adrenomedullin and proadrenomedullin N-terminal 20 peptide induce histamine release from rat peritoneal mast cell.

Adrenomedullin (ADM)-induced histamine release from rat peritoneal mast cells was investigated. We compared the ability of full-length ADM to induce histamine release to the fragments ADM-(1-25) and ADM-(22-52), as well as proadrenomedullin N-terminal 20 peptide (PAMP). ADM (10(-8) to 10(-5) M) and PAMP (10(-8) to 10(-5) M) dose-dependently increased histamine release from peritoneal mast cell preparations. The effect of ADM-(1-25) was similar to ADM, whereas ADM-(22-52) did not show any effects. These data suggest the relative importance of the ADM C-terminal fragment, which contains a six-membered ring structure. Histamine release, induced by ADM, was significantly and dose-dependently inhibited by the addition of ADM-(22-52) (10(-5) M), Ca(2+) (0.5 to 2.0 mM), and benzalkonium chloride (3 to 7 microM), a selective inhibitor of Gi type G proteins. In contrast, PAMP (10(-5) M)-induced histamine release was not inhibited by Ca(2+). These results suggest that ADM induce histamine release via a putative ADM receptor in a manner sensitive to Gi-protein function and extracellular Ca(2+) concentration, and that PAMP might produce its effect by a different mechanism than ADM.

Cardiac functional and structural alterations induced by endotoxin in rats: importance of platelet-activating factor.

OBJECTIVE: In this study, we evaluated the time course of the alterations in left ventricular (LV) dimensions, LV wall thickness, and LV systolic function in rats with endotoxemia by using echocardiography as well as myocardial histopathologic assessments. Our second goal was to examine whether pretreatment with a platelet-activating factor (PAF) antagonist would ameliorate the lipopolysaccharide (LPS)-induced cardiovascular collapse during the early phase. DESIGN: A prospective, controlled, in vivo animal laboratory study. SETTING: Research laboratory at a university. SUBJECTS: Male, Wistar rats (8-9 wks old; n = 83). INTERVENTIONS: In pentobarbital-anesthetized rats, the right carotid artery was cannulated to measure the arterial blood pressure and to sample blood. The right jugular vein also was catheterized for the administration of drugs. LPS (2 mg/kg) derived from Klebsiella pneumoniae or physiologic saline was administered in the presence or absence of pretreatment with TCV-309, a specific potent PAF antagonist. Echocardiographic studies were performed with an 8- to 13-MHz transducer. MEASUREMENTS AND MAIN RESULTS: LPS administration immediately induced progressive hypotension. The maximal hypotensive response was observed at 10 mins after LPS infusion with mean arterial pressure decreasing from 119 +/- 2 to 56 +/- 3 mm Hg (p < .001). LV end-diastolic internal dimensions decreased from 6.4 +/- 0.1 to 3.1 +/- 0.1 mm (p < .001) at 30 mins after LPS and remained significantly reduced compared with control rats. LV end-systolic dimensions also decreased dramatically from 3.5 +/- 0.2 to 0.5 +/- 0.1 mm (p < .001) at 30 mins after LPS and remained significantly reduced throughout the experiment. LV fractional shortening increased from 45 +/- 1% to 84 +/- 2% (p < .001) at 30 mins after LPS and remained elevated compared with control rats. LV wall thickness increased strikingly from 15 mins until 2 hrs after LPS infusion. Pathologic studies demonstrated marked congestion of capillaries and mild edema in the LV myocardium. The hematocrit increased after the administration of LPS. LPS markedly increased sympathetic tone as demonstrated by the elevation of plasma concentrations of epinephrine and norepinephrine. There was no elevation of concentrations of nitrite and nitrate. Pretreatment with TCV-309, a specific potent PAF antagonist, reduced LPS-induced hypotension and attenuated LV functional and structural changes. TCV-309 administration reduced the LPS-induced adrenergic activation and hemoconcentration. CONCLUSIONS: The hypotension that occurred during the initial phase of LPS-induced shock was accompanied by LV functional and structural alterations. The marked increase in LV wall thickness can be ascribed to the congestion of capillaries and edema in the LV myocardium. Pretreatment with a PAF antagonist reduced LPS-induced alterations. PAF may play a pivotal role during the initial phase of LPS-induced cardiovascular responses.

[Pharmacokinetic behavioral changes of methamphetamine in methamphetamine-sensitized animal model].

There has been an increased population of users and abusers of amphetamines, including methamphetamines (METH), in the past two decades, and this has become a crucial social problem in Japan. METH abusers show a paranoid schizophrenia-like syndrome, including paranoid hallucination and delusion, and repeated exposure to these drugs will enhance their effects; i.e. the behavioral and reinforcing effects of abusing drugs became progressively and irreversibly developed (behavioral sensitization) in humans and in experimental animals. Although numerous neuropsychopharmacological/neurochemical studies on behavioral sensitization were conducted, few reports are available to understand the pharmacokinetic aspect of METH, including the brain penetration of METH, in this phenomenon. The present report reviews previous pharmacokinetic studies for METH and our findings in rats having behavioral sensitization to METH, especially from the point of view regarding the relationship of drug transporters.

Intradermal application of nociceptin increases vascular permeability in rats: the possible involvement of histamine release from mast cells.

Intradermal application of nociceptin was used to investigate its in vivo effect on the inflammatory response in rats. Intradermal nociceptin (5 pmol/site-5 nmol/site) increased vascular permeability in a dose-dependent manner. The increased vascular permeability by nociceptin (5 nmol/site) was dose-dependently inhibited by the histamine H1 receptor antagonist pyrilamine (50 pmol/site-5 nmol/site). In rat peritoneal mast-cell preparation, nociceptin (10(-8)-10(-4) M) dose-dependently stimulated histamine release. The effect of nociceptin (10(-5) M) occurred rapidly (within 30 s) and was inhibited by pertussis toxin, Ca2+, but was not sensitive to naloxone, a classical opioid receptor antagonist. These characteristics are in agreement with features of the opioid-receptor-like 1 (ORL1) receptor, a non-classical opioid receptor linked to a pertussis toxin-sensitive G protein. Taken together, these data suggest that nociceptin, likely acting via the ORL1 receptor at the site of inflammation, might be critical for the enhancement of the inflammatory response by stimulating histamine release from mast cells.

Inhibitory effect of erythromycin on P-glycoprotein-mediated biliary excretion of doxorubicin in rats.

The macrolide antibiotic erythromycin has recently been shown to overcome the resistance to anticancer drugs that results from overexpression of P-glycoprotein. The present study, using erythromycin lactobionic acid as a model drug, investigated the inhibitory effects of erythromycin on the efflux of doxorubicin from P388/ADR cells expressing P-glycoprotein and on the biliary excretion mechanism of doxorubicin in rats, which is primarily mediated by P-glycoprotein. Erythromycin lactobionic acid was found to inhibit the efflux of doxorubicin (5 microM) from P388/ADR cells in a concentration-dependent manner. In rats receiving constant-rate infusion of doxorubicin (30 micrograms/min), both the biliary and renal clearance of this drug dramatically decreased and its plasma concentrations increased after an intravenous injection of erythromycin lactobionic acid (100 mg/kg as erythromycin). These results suggest that erythromycin competitively inhibits P-glycoprotein-mediated biliary and renal excretion of doxorubicin. The effect of erythromycin on the biliary secretion of doxorubicin was also analyzed quantitatively by the competitive inhibition model. The computer-estimated values of Vmax/Km, Km and Ki were 8.79 ml/minute, 0.82 microgram/ml and 0.41 microgram/ml, respectively. The findings of these experiments suggest that the inhibitory effect of erythromycin on the P-glycoprotein-mediated biliary excretion of doxorubicin is competitive and that combination chemotherapy of doxorubicin with erythromycin may induce toxicity as a result of increased plasma concentrations of doxorubicin.

Reversal of anticancer drug resistance by macrolide antibiotics in vitro and in vivo.

1. The combined effects of the macrolide antibiotics erythromycin, josamycin, clarithromycin and YM17K (3,4'-dideoxy mycaminosyl tylonolide hydrochloride) on in vitro intracellular accumulation of vinblastine or cyclosporine (Cs)A and on the in vivo antitumour activity of vinblastine were investigated using mouse leukaemia P388 cells (P388/S) and anticancer drug-resistant (P388/ADR) cells. These effects were compared with those of a calcium antagonist (verapamil) or immunosuppressants (FK506 and CsA). 2. All tested macrolide antibiotics increased the accumulation of both vinblastine and CsA in P388/ADR cells in a dose-dependent manner, but their potency was lower than that of verapamil, CsA or FK506. 3. When vinblastine (200 microg/kg) was administered intraperitoneally with each of the macrolide antibiotics (10 or 100 mg/kg) or with verapamil (25 mg/kg) once a day for 10 days in P388/ADR-bearing mice, combined effects of vinblastine with the macrolide antibiotics (erythromycin, clarithromycin and YM17K) or verapamil were observed. 4. The present study suggests that macrolide antibiotics may overcome anticancer drug resistance by inhibiting the binding of vinblastine or CsA to P-glycoprotein in P388/ADR cells. 5. We believe that these results are encouraging for combination chemotherapy to overcome P-glycoprotein-dependent anticancer drug-resistant tumours in clinical practice.

Dopamine D-5 receptor modulates hippocampal acetylcholine release.

Dopamine is intimately involved in cognitive processes in the brain. Of the several subtypes of dopamine receptors, the possible role of dopamine D1-like receptors in brain functions, especially in learning and memory, has recently generated much interest. However, molecularly the D1-like receptors are comprised of at least two subtypes, namely D-1 and D-5, and it has not been possible to ascertain which of these two receptor classes is responsible for these functions due to the lack of selective ligands. In the present study, utilizing a combined antisense-in vivo dialysis approach, we show that the D-5 subtype is the dopamine D1-like receptor involved in modulating hippocampal acetylcholine (ACh) release, a transmitter implicated in a variety of cognitive processes. This is one of the first evidence for a functional role for the D-5 receptor.

Increased vasomotor sympathetic nerve activity and decreased plasma nitric oxide release after head-down bed rest in humans: disappearance of correlation between vasoconstrictor and vasodilator.

We hypothesized that the relationship between resting levels of sympathetic vasoconstrictor nerve traffic and dilator substance nitric oxide (NO) release is altered after exposure to microgravity, resulting in abnormal peripheral resistance. To examine the hypothesis, we assessed muscle sympathetic nerve activity (MSNA) (microneurography), an indicator of NO release (plasma nitrite/nitrate concentrations) and leg vascular resistance (venous occlusion plethysmography) in 20 healthy male volunteers before and after 14 days of 6 degrees head-down bed rest (HDBR), the ground-based analogue of microgravity. MSNA increased, while plasma nitrite/nitrate concentrations decreased after HDBR. A significant positive correlation observed between MSNA and plasma nitrite/nitrate concentrations before HDBR disappeared after HDBR. Leg vascular resistance increased after HDBR. In conclusion, an imbalance between sympathetic vasoconstrictor traffic and NO release might contribute to elevated peripheral vascular resistance following HDBR.

Expression of the purported sigma(1) (sigma(1)) receptor in the mammalian brain and its possible relevance in deficits induced by antagonism of the NMDA receptor complex as revealed using an antisense strategy.

Sigma (sigma) receptors have generated a great deal of interest on the basis of their possible role in psychosis, neuroprotection and various other behaviors including learning processes. The existence of at least two classes of sigma receptor binding sites (sigma(1) and sigma(2)) is now well established. The recent cloning of the mouse, guinea pig and human sigma(1) receptors has allowed the study of the discrete distribution of the sigma(1) receptor mRNA in rodent and human brain tissues using in situ hybridization. Overall, the sites of expression of specific sigma(1) receptor mRNA signals were in accordance to the anatomical distribution of sigma(1) receptor protein first established by quantitative receptor autoradiography. Specific sigma(1) receptor hybridization signals were found to be widely, but discretely distributed, in mouse and guinea pig brain tissues. The highest levels of transcripts were seen in various cranial nerve nuclei. Lower, but still high hybridization signals were observed in mesencephalic structures such as the red nucleus, periaqueductal gray matter and substantia nigra, as well as in some diencephalic structures including such as the habenula and the arcuate, paraventricular and ventromedial hypothalamic nuclei. Superficial (I-II) and deeper (IV-VI) cortical laminae were moderately labeled in the mouse brain. Moderate levels of sigma(1) receptor mRNA were also found in the pyramidal cell layer and the dentate gyrus of the hippocampal formation. Other structures such as the thalamus and amygdaloid body also expressed the sigma(1) receptor mRNA although to a lesser extent. In murine peripheral tissues, strong hybridization signals were observed in the liver, white pulp of the spleen and the adrenal gland. In the postmortem human brain, moderate levels of sigma(1) receptor mRNA, distributed in a laminar fashion, were detected in the temporal cortex with the deeper laminae (IV-VI) being particularly enriched. In the hippocampal formation, the strongest hybridization signals were observed in the dentate gyrus while all other subfields of the human hippocampal formation expressed lower levels of the sigma(1) receptor mRNA. Antisense oligodeoxynucleotides against the purported sigma(1) receptor were used next to investigate the possible role of this receptor in dizocilpine (MK-801)/NMDA receptor blockade-induced amnesia. Following a continuous intracerebroventricular infusion of a specific sigma(1) receptor antisense into the third ventricle (0.4 nmol/h for 5 days), sigma(1)/[3H](+)pentazocine binding was significantly reduced in mouse brain membrane homogenates while a scrambled antisense control was without effect. Moreover, the sigma(1) receptor antisense treatments (5 nmol/injection, every 12 hx3 or 0.4 nmol/h for 5 days) attenuated (+)MK-801/NMDA receptor blockade-induced cognitive deficits in the treated mice while a scrambled antisense control had no effect. Taken together, these results demonstrate the widespread, but discrete, distribution of the sigma(1) receptor mRNA in the mammalian central nervous system. Moreover, antisense treatments against the purported sigma(1) receptor gene reduced specific sigma(1)/[3H](+)pentazocine binding and modulated cognitive behaviors associated with NMDA receptor blockade providing further evidence for the functional relevance of the cloned gene.

A novel muscarinic M(4) receptor antagonist provides further evidence of an autoreceptor role for the muscarinic M(2) receptor sub-type.

Muscarinic M(2) (AF-DX 384, BIBN-161) and M(4) (PD102807) receptor antagonists were used to investigate the respective roles of these two receptor sub-types in the regulation of acetylcholine release in the rat hippocampus. In vivo dialysis studies revealed that only the muscarinic M(2) receptor antagonists significantly and concentration-dependently facilitate acetylcholine release. The newly developed muscarinic M(4) receptor antagonist was unable to regulate acetylcholine release except at the highest concentration tested. It would thus appear that the muscarinic receptor acting as negative autoreceptor in the rat hippocampus is of the muscarinic M(2) sub-type, the role of the muscarinic M(4) receptor being minimal in this regard.

Effects of bacterial endotoxin on drug pharmacokinetics.

Bacterial endotoxin (lipopolysaccharide) has a variety of biological and immunological activities. Endotoxin-induced physiological changes in several organs might modify the pharmacokinetic behavior, including the biliary and urinary excretions and hepatic metabolism, of various drugs. We have conducted a series of studies as part of a program for the development of guidelines for the safe use of various drugs in patients with Gram-negative bacterial infections. We have found that endotoxin isolated from Klebsiella pneumoniae dramatically reduces renal and biliary excretion of organic anionic drugs actively secreted into the urine and bile, respectively. More recently, we found that K. pneumoniae endotoxin decreases the activity of cytochrome P450-mediated drug-metabolizing enzymes in a time-dependent manner. This article reviews recent progress in the description of pharmacokinetic properties of drugs during conditions of endotoxemia, focusing especially upon the effects of K. pneumoniae endotoxin on the hepatic metabolism and biliary excretion of drugs, and the relationship between pharmacokinetic changes and various endotoxin-induced mediators.