Inhibition of IK,ACh current may contribute to clinical efficacy of class I and class III antiarrhythmic drugs in patients with atrial fibrillation

Inward rectifier potassium currents I_K1 and acetylcholine activated I_K,ACh are implicated in atrial fibrillation (AF) pathophysiology. In chronic AF (cAF), I_K,ACh develops a receptor-independent, constitutively active component that together with increased I_K1 is considered to support maintenance of AF. Here, we tested whether class I (propafenone, flecainide) and class III (dofetilide, AVE0118) antiarrhythmic drugs inhibit atrial I_K1 and I_K,ACh in patients with and without cAF. I_K1 and I_K,ACh were measured with voltage clamp technique in atrial myocytes from 58 sinus rhythm (SR) and 35 cAF patients. The M-receptor agonist carbachol (CCh; 2 μM) was employed to activate I_K,ACh. In SR, basal current was not affected by either drug indicating no effect of these compounds on I_K1. In contrast, all tested drugs inhibited CCh-activated I_K,ACh in a concentration-dependent manner. In cAF, basal current was confirmed to be larger than in SR (at −80 mV, −15.2 ± 1.2 pA/pF, n = 88/35 vs. −6.5 ± 0.4 pA/pF, n = 194/58 [myocytes/patients]; P < 0.05), whereas CCh-activated I_K,ACh was smaller (−4.1 ± 0.5 pA/pF vs. −9.5 ± 0.6 pA/pF; P < 0.05). In cAF, receptor-independent constitutive I_K,ACh contributes to increased basal current, which was reduced by flecainide and AVE0118 only. This may be due to inhibition of constitutively active I_K,ACh channels. In cAF, all tested drugs reduced CCh-activated I_K,ACh. We conclude that in cAF, flecainide and AVE0118 reduce receptor-independent, constitutively active I_K,ACh, suggesting that they may block I_K,ACh channels, whereas propafenone and dofetilide likely inhibit M-receptors. The efficacy of flecainide to terminate AF may in part result from blockade of I_K,ACh.     

Occupancy of dopamine D<Subscript>1</Subscript>, D<Subscript>2</Subscript> and serotonin<Subscript>2A</Subscript> receptors in schizophrenic patients treated with flupentixol in comparison with risperidone and haloperidol

Rationale Flupentixol (FLX) has been used as a neuroleptic for nearly 4 decades. In vitro data show comparable affinity to dopamine D₂, D₁ and 5-HT_2A receptors and recently, FLX showed to be not inferior to risperidone in schizophrenic patients with predominant negative symptomatology, which was implicated with flupentixol’s interaction with 5-HT_2A and/or D₁ receptors. Objectives To assess in vivo receptor occupancy (RO) in patients clinically treated with FLX (n = 13, 5.7 ± 1.4 mg/day) in comparison with risperidone (RIS, n = 11, 3.6 ± 1.3 mg/day) and haloperidol (HAL, n = 11, 8.5 ± 5.5 mg/day). Materials and methods Each patient underwent two PET scans with 3-N-[¹¹C]methylspiperone (target: frontal 5-HT_2A), [¹¹C]SCH23390 (striatal D₁) or [¹¹C]raclopride (striatal D₂). RO was calculated as the percentage reduction of specific binding in comparison with healthy controls. Results D₂-RO under FLX was between 50% and 70%, indicating an ED₅₀ of about 0.7 ng/ml serum. 5-HT_2A and D₁-RO was 20 ± 10% and 20 ± 5% (mean, SEM). Under HAL, D₁-RO was 14 ± 6% and under RIS not significantly different from zero. Conclusions We were able to demonstrate a moderate 5-HT_2A and D₁ occupancy under clinically relevant doses of flupentixol, albeit lower than expected from in vitro data and clearly below saturation. Therefore, if flupentixol’s efficacy on negative symptoms is based on its interaction with 5-HT_2A and/or D₁ receptors, it should be highly dependent on serum concentration and thus on dosage and metabolism. However, these data suggest that mechanisms other than D₁ or 5-HT_2A antagonism may contribute to flupentixol’s efficacy on negative symptoms.     

Changes in urinary PGE<Subscript>2</Subscript> after ibuprofen treatment in preterm infants with patent ductus arteriosus

Purpose  To investigate changes in urinary PGE₂ after ibuprofen treatment in preterm infants with patent ductus arteriosus (PDA). Methods  Twenty preterm infants with a hemodynamically significant PDA (gestational age, 28.6 ± 2.3 weeks) and 20 controls (gestational age, 30.4 ± 1.5 weeks) were prospectively enrolled at 48–72 h of life. After enrollment, the former underwent conventional ibuprofen-lysine treatment. At 48–72 h (T₀) and 108–144 h of life (T₁), urine samples were noninvasively collected in both groups to measure urinary PGE₂ concentrations (enzyme immunoassay method), and renal function was investigated. Results  Urinary PGE₂ decreased significantly both in ibuprofen-treated patients (66.95 ± 16.78 vs. 27.15 ± 17.92 pg/mL, P < 0.001) and in controls (71.7 ± 16.2 vs. 53.2 ± 18.4 pg/mL, P < 0.001) from T₀ to T₁. However, urinary PGE₂ at T₁ was significantly lower (P < 0.001) in the ibuprofen group compared to the control group. Acute renal failure occurred in three ibuprofen-treated patients (15%). Conclusions  Ibuprofen markedly reduces (59.4%) urinary PGE₂ and may alter renal function in the newborn.     

Proline Prodrug of Melphalan Targeted to Prolidase,a Prodrug Activating Enzyme Overexpressed in Melanoma

Purpose To determine the bioactivation and uptake of prolidase-targeted proline prodrugs of melphalan in six cancer cell lines with variable prolidase expression and to evaluate prolidase-dependence of prodrug cytotoxicity in the cell lines compared to that of the parent drug, melphalan. Materials and Methods Hydrolysis, cell uptake, and cell proliferation studies of melphalan and the L- and D-proline prodrugs of melphalan, prophalan-L and prophalan-D, respectively, were conducted in the cancer cell lines using established procedures. Results The bioactivation of prophalan-L in the cancer cell lines exhibited high correlation with their prolidase expression levels (r ² = 0.86). There were no significant differences in uptake of melphalan and its prodrugs. The cytotoxicity of prophalan-L (GI₅₀) in cancer cells also showed high correlation with prolidase expression (r ² = 0.88), while prophalan-D was ineffective at comparable concentrations. A prolidase targeting index (ratio of melphalan to prophalan-L cytotoxicity normalized to their uptake) was computed and showed high correlation with prolidase expression (r ² = 0.82). Conclusions The data corroborates the specificity of prophalan-L activation by prolidase as well as prolidase-targeted cytotoxicity of prophalan-L in cancer cell lines. Hence, prophalan-L, a stable prodrug of melphalan, exhibits potential for efficiently targeting melanoma with reduced systemic toxicity.     

苄基四氢巴马汀对豚鼠心室肌细胞钾电流及钙、钠电流的作用

目的：研究苄基四氢巴马汀（BTHP）对心肌细胞的作用特点,以探讨其抗心律失常机制。方法：用全细胞膜片钳技术考察BTHP对心室肌细胞钾电流及钙、钠电流的作用。结果：BTHP 30 μmol.L^-1明显阻滞延迟整流钾电流（I_K包括：I_Kr及I_Ks）。可使I_Kr及I_Kr,tail的幅值下降,且对I_Kr阻滞作用呈频率依赖性;对I_Ks及I_Ks,tail幅值也有明显的抑制作用。BTHP 200　μmol.L^-1可明显阻滞I_Ca,L,使其电流幅值降低,但对I_K1,I_Ca,T,I_Na电流均无影响。结论：BTHP可明显阻滞心室肌细胞I_Kr,I_Ks,I_Ca,L电流,且对I_Kr阻滞作用呈频率依赖性。     

Effects of flavoxate hydrochloride on voltage-dependent Ba<Superscript>2+</Superscript> currents in human detrusor myocytes at different experimental temperatures

The inhibitory effects of flavoxate hydrochloride (piperidinoethyl-3-methylflavone-8-carboxylate; hereafter referred as flavoxate) on voltage-dependent nifedipine-sensitive inward Ba²⁺ currents (I _Ba) in human detrusor myocytes were investigated at different temperatures using conventional whole-cell patch-clamp techniques. When the bath-solution temperature was increased from 22°C to 30°C, I _Ba peak amplitude was enhanced by approximately twice at several test potentials. Neither the I _Ba threshold nor the membrane potentials for the I _Ba maximum peak amplitude was affected by the temperature change. The concentration-response curves of flavoxate at both 30°C (K _i  = 5.1 μM) and 37°C (K _i  = 4.6 μM) were slightly shifted to the left in comparison with that at 22°C (K _i  = 10.3 μM). Similar results were also obtained in the presence of nifedipine (K _i  = 14 nM at 22°C vs. K _i  = 2.5 nM at 30°C and K _i  = 2.1 nM at 37°C). Altering the bath-solution temperature from 22°C to 30°C shifted the steady-state inactivation curve of I _Ba at −90 mV to the left. At 30°C, the steady-state inactivation curve of I _Ba in the presence of flavoxate was also shifted to the left in comparison with that in the absence of flavoxate. Either 3-isobutyl-1-methylxanthine (IBMX) or theophylline, a phosphodiesterase inhibitor, caused little effects on I _Ba, although cyclic nucleotides (dibutyryl cAMP and 8-Br-cGMP) inhibited I _Ba. These results suggest that the inhibitory actions of flavoxate on I _Ba in human detrusor myocytes were slightly changed at different experimental temperatures and that flavoxate directly blocked voltage-dependent L-type Ca²⁺ channels, not through the inhibition of phosphodiesterase activity pathway.     

Dexmedetomidine inhibits muscarinic type 3 receptors expressed in <Emphasis Type="Italic">Xenopus</Emphasis> oocytes and muscarine-induced intracellular Ca<Superscript>2+</Superscript> elevation in cultured rat dorsal root ganglia cells

Dexmedetomidine, an α₂-adrenoceptor agonist, has been approved for clinical use, although the mechanism of dexmedetomidine action has not been fully elucidated. Several studies have shown that G protein-coupled receptors (GPCRs) are recognized as targets for anesthetics and analgesics. Therefore, it is of interest to determine whether dexmedetomidine affects the function of GPCRs other than the α₂-adrenoceptor. We examined the effects of dexmedetomidine on M₁, M₃, 5-HT_2C, substance P, and orexin 1 receptors in Xenopus oocytes expressing individual receptors. In addition, we investigated the effects of dexmedetomidine on muscarinic receptor-mediated changes in [Ca²⁺]_i in the dorsal root ganglia (DRG) of 3-week-old Wister rats. Dexmedetomidine did not affect the 5-HT_2C-, or substance P-induced Cl⁻ currents and had little inhibition on the orexin A-induced current in oocytes expressing the respective receptors. The compound also had little effect on the acetylcholine (ACh, 1 μM)-induced Ca²⁺-activated Cl⁻ currents in Xenopus oocytes expressing M₁ receptors. In contrast, dexmedetomidine inhibited the ACh-induced currents in Xenopus oocytes expressing M₃ receptors; 1 nM, 10 nM, 100 nM, and 1 μM dexmedetomidine reduced the current to 66.5 ± 4.8, 51.3 ± 12, 34.6 ± 11, and 26.8 ± 6.4% of the control value, respectively (EC₅₀ = 3.5 ± 0.7 nM). Dexmedetomidine reduced the ACh-induced Cl⁻ currents after treatment with the selective protein kinase C inhibitor GF109203X. Moreover, the compound inhibited the muscarinic receptor-mediated increases in [Ca²⁺]_i in cultured DRG cells in a concentration-dependent manner. Dexmedetomidine inhibits the function of M₃ receptors, in addition to its agonistic effects on α₂-adrenoceptors, which provides further insight into the pharmacological properties of dexmedetomidine.     

Effects of Cd<Superscript>2+</Superscript> on transient outward and delayed rectifier potassium currents in acutely isolated rat hippocampal CA1 neurons

The effects of cadmium (Cd²⁺) on the transient outward potassium current (I _A) and delayed rectifier potassium current (I _K) were investigated in acutely dissociated rat hippocampal CA1 neurons using the whole-cell patch-clamp technique. The results showed that Cd²⁺ inhibited the amplitudes of I _A and I _K in a reversible and concentration-dependent manner, with half-maximal inhibitive concentration (IC₅₀) values of 546 ± 59 and 749 ± 53 μM, and the inhibitory effect of Cd²⁺ was voltage dependent. Cd²⁺ significantly shifted the steady-state activation and inactivation curve of I _A to more positive potentials. In contrast, Cd²⁺ caused a relatively less but still significant positive shift in the activation of I _K without effect on the inactivation curve. Cd²⁺ significantly slowed the recovery from inactivation of I _K but had no effect on the recovery time course of I _A. The results suggest that the modulation of I _A and I _K was most likely mediated by the interaction of Cd²⁺ with a specific site on the potassium-channel protein rather than by screening of bulk surface-negative charge. The effects of Cd²⁺ on the voltage-gated potassium currents may be a possible contributing mechanism for the Cd²⁺-induced neurotoxic damage. In addition, the effects of Cd²⁺ on the potassium currents at concentrations that overlap with its effects on calcium currents raise concerns about its use in pharmacological or physiological studies.     

Distribution and metabolism of N G-nitro-l-arginine methyl ester in patients with septic shock

Objective: The pharmacokinetics of N ^G-nitro-l-arginine methyl ester (l-NAME), an inhibitor of nitric oxide (NO) synthesis, was investigated in patients with septic shock. Methods: Blood was sampled at intervals before, during and after 12-h infusion of l-NAME 1 mg · kg⁻¹ · h⁻¹ in nine septic shock patients for determination of plasma concentrations by high-performance liquid chromatography (HPLC). In three patients the renal clearance of the drug was determined. Results: Incubation of l-NAME with plasma and blood in vitro revealed hydrolysis to N ^G-nitro-l-arginine (l-NOARG), the active inhibitor of NO synthesis. l-NOARG did not undergo further degradation. Continuous intravenous infusion of 1 mg · kg⁻¹ · h⁻¹ of l-NAME for 12 h in patients with septic shock increased blood pressure and resulted in increasing plasma concentrations of l-NOARG (C_max 6.2 μg · ml⁻¹ at 12 h) whereas l-NAME concentrations reached a plateau within 1.5 h (C_max 1.0 μg · ml⁻¹). After the infusion was stopped l-NAME disappeared from the plasma rapidly (half-life 19.2 min) whereas l-NOARG concentration declined slowly (half-life 22.9 h). The calculated volume of distribution for l-NAME was 0.45 l · kg⁻¹ body weight and 1.96 l · kg⁻¹ for l-NOARG. The renal clearance for l-NOARG was 3.5% of total body clearance for l-NOARG, whereas l-NAME could not be detected in urine. Conclusion: We conclude that vasoconstriction with l-NAME in septic patients may result from hydrolysis to l-NOARG, the active inhibitor of NO synthesis. The long plasma half-life and large volume of distribution for l-NOARG suggests extensive distribution to extravascular tissues. Since renal excretion is minimal, elimination of the metabolite l-NOARG follows other pathways. Received: 13 March 1998 / Accepted in revised form: 30 June 1998     

Role of tumour necrosis factor‐a in the regulation of T‐type calcium channel current in HL‐1 cells

Increasing evidence indicates that inflammation contributes to the initiation and perpetuation of atrial fibrillation (AF). Although tumour necrosis factor (TNF)‐α levels are increased in patients with AF, the role of TNF‐α in the pathogenesis of AF remains unclear. Besides L‐type Ca²⁺ currents (I_Ca,L), T‐type Ca²⁺ currents (I_Ca,T) also plays an important role in the pathogenesis of AF. This study was designed to use the whole‐cell voltage‐clamp technique and biochemical assays to explore if TNF‐α is involved in the pathogenesis of AF through regulating I_Ca,T in atrial myocytes. It was found that compared with sinus rhythm (SR) controls, T‐type calcium channel (TCC) subunit mRNA levels were decreased, while TNF‐α expression levels were increased, in human atrial tissue from patients with AF. In murine atrial myocyte HL‐1 cells, after culturing for 24 h, 12.5, 25 and 50 ng/mL TNF‐α significantly reduced the protein expression levels of the TCC α1G subunit in a concentration‐dependent manner. The peak current was reduced by the application of 12.5 or 25 ng/mL TNF‐α in a concentration‐dependent manner (from ?15.08 ± 1.11 pA/pF in controls to ?11.89 ± 0.83 pA/pF and ?8.54 ± 1.55 pA/pF in 12.5 or 25 ng/mL TNF‐α group respectively). TNF‐α application also inhibited voltage‐dependent inactivation of I_Ca,T, shifted the inactivation curve to the left. These results suggest that TNF‐α is involved in the pathogenesis of AF, probably via decreasing I_Ca,T current density in atrium‐derived myocytes through impaired channel function and down‐regulation of channel protein expression. This pathway thus represents a potential pathogenic mechanism in AF.     

Mitochondrial K<Subscript>ATP</Subscript> channels participate in the limitation of infarct size by cariporide

The objective of this study is to assess the participation of mitochondrial ATP-sensitive potassium (mitoK_ATP) channels in the cardioprotective effects of the Na⁺/H⁺ exchanger (NHE-1) blocker cariporide in isolated rat hearts. Regional ischemia was induced by occlusion of left anterior descending coronary artery during 40 min followed by 2-h reperfusion (IC). Cariporide (C, 10 μΜ), or C plus 5-hydroxydecanoate (5-HD, 100 μM, a selective mitoK_ATP channel inhibitor), or C plus chelerythrine (Chele, 1 μM, a PKC inhibitor), or an opener of mitoK_ATP channels, diazoxide (Dz, 100 μM) was applied at the onset of reperfusion. Infarct size (IS) and myocardial function were evaluated. The calcium-induced permeability transition pore (mPTP) opening was determined by measuring the light scattering decrease (LSD, a.u.) in isolated mitochondria in the absence and presence of C, C + 5-HD and Dz. IS was 33 ± 2% of the risk area in IC and was significantly diminished by C (15 ± 2%, p < 0.05), which also improved myocardial function [LVDP = 58 ± 5% (IC) vs 80 ± 5% (C)] and blunted LSD [0.80 ± 0.04 (IC) vs 0.51 ± 0.04 (C) a.u.]. 5-HD and Chele were both able to abolish the cardioprotective effects of C on IS. Dz treatment decreased IS and LSD to a similar extent to that produced by C (15 ± 4% and 0.52 ± 0.04 a.u., respectively). The present data suggest that attenuation of mPTP opening after PKC-mediated mitoK_ATP channel activation is a crucial step for the cardioprotective effects of cariporide.     

Discriminative stimulus and reinforcing effects of <Emphasis Type="Italic">p</Emphasis>-fluoro-<Emphasis Type="SmallCaps">l</Emphasis>-deprenyl in monkeys

Rationale para-Fluoro-l-deprenyl (Fludepryl), a halogenated derivative of l-deprenyl, shares structural similarities with amphetamine and may have potential as a medication for psychostimulant abuse. Objectives p-Fluoro-l-deprenyl was evaluated for psychomotor stimulant, discriminative stimulus, and reinforcing effects in squirrel monkeys. Methods One group of monkeys was trained under a ten-response fixed-ratio (FR10) schedule of stimulus termination to discriminate between methamphetamine (0.32 mg/kg, i.m.) and saline. Other monkeys were trained to self-administer i.v. cocaine under either a simple FR10 schedule or a second-order fixed-interval 5-min schedule with FR10 components. Results Full generalization to the methamphetamine-training stimulus was produced by an i.m. dose of 10.0 mg/kg p-fluoro-l-deprenyl. l-Deprenyl and the metabolites of p-fluoro-l-deprenyl, p-fluoro-l-amphetamine, and p-fluoro-l-methylamphetamine were more potent, producing full generalization at doses of 1.0–3.2 mg/kg. Under the FR10 schedule of drug injection, persistent self-administration behavior was maintained by i.v. cocaine injections but not by injections of vehicle or injection doses of p-fluoro-l-deprenyl up to 1.0 mg/kg. However, p-fluoro-l-deprenyl did maintain moderate levels of i.v. self-administration responding under the second-order schedule of drug injection. Peak response rates maintained by 0.1-mg/kg injections of p-fluoro-l-deprenyl were significantly greater than those associated with saline substitution, yet significantly lower than those maintained by cocaine or d-amphetamine. Conclusions p-Fluoro-l-deprenyl has methamphetamine-like discriminative-stimulus properties in squirrel monkeys that appear at higher doses than for its parent compound, l-deprenyl. It also appears to function as a relatively limited reinforcer of intravenous self-administration behavior in monkeys trained to self-administer i.v. cocaine.     

Effect of nitroxyalkyl derivatives of fullerenylproline on the activity of CA<Superscript>3+</Superscript>-ATPase of sarcoplasmic reticulum

The effect of nitroxyalkyl derivatives of fullerenylproline methyl ester on the enzymatic activity of Ca²⁺-ATPase of sarcoplasmic reticulum (SR) has been studied. It is shown that hybrid derivatives of C₆₀ fullerene are capable of inhibiting the activity of Ca²⁺-ATPase of SR. The mononitrate inhibits the hydrolytic activity of the enzyme with K _i = 1.92 × 10⁻⁶ M; active Ca²⁺ transport, with K _i = 3.79 × 10⁻⁶ M. The dinitrate inhibits ATP hydrolysis with K _i = 2.38 × 10⁻⁸ M; Ca²⁺ transport, with K _i  = 3.08 × 10⁻⁸ M. Fullerenylproline methyl ester does not affect the enzymatic activity of Ca²⁺-ATPase. Based on these data it is possible to predict the possible fields of application for hybrid fullerene derivatives as potential drugs.     

New triterpenoid saponins from <Emphasis Type="Italic">Argania spinosa</Emphasis>

Five new triterpene saponins, arganine L (1), O (2), P (3), Q (4) and R (5), were isolated from the barks of Argania spinosa (L.) Skeels. Arganines L-P and R are bidesmosidic saponins. The structures of 1–5 were elucidated as 3-O-[β-d-xylopyranosyl-(1–4)-β-d-glucuronopyranosyl]-28-O-[β-d-apiofuranosyl-(1–3)-β-d-xylopyranosyl-(1–4)-α-l-rhamnopyranosyl-(1–2)-α-l-arabinopyranosyl] bayogenin, 3-O-[β-d-xylopyranosyl-(1–4)-β-d-glucuronopyranosyl]-28-O-[β-d-xylopyranosyl-(1–4)-α-l-arabinopyranosyl] bayogenin, 3-O-[β-d-xylopyranosyl-(1–4)-β-d-glucuronopyranosyl]-28-O-[α-l-arabinopyranosyl] bayogenin, 3-O-[β-d-xylopyranosyl-(1–4)-β-d-glucuronopyranosyl] bayogenin, and 3-O-[β-d-apiofuranosyl-(1–4)-β-d-glucuronopyranosyl]-28-O-[β-d-xylopyranosyl-(1–4)-α-l-rhamnopyranosyl-(1–2)-α-l-arabinopyranosyl] bayogenin, respectively, mainly on the basis of their spectroscopic data.     

Interethnic differences of <Emphasis Type="Italic">PEPT2</Emphasis> (<Emphasis Type="Italic">SLC15A2</Emphasis>) polymorphism distribution and associations with cephalexin pharmacokinetics in healthy Asian subjects

Objectives  The aims of this study were to characterize the population frequency of PEPT2 (SLC15A2) polymorphic variants in three Asian ethnic populations, namely Chinese, Malay and Asian Indian, and to investigate the associations of ethnicity (Chinese vs. Asian Indian), PEPT2 haplotype and cephalexin pharmacokinetics in healthy Asian subjects. Methods   PEPT2 polymorphisms were screened from a cohort of 96 Chinese, 96 Malay and 96 Asian Indian subjects. Cephalexin (1000 mg, orally) pharmacokinetics was characterized in an additional 15 Chinese and 15 Asian Indian healthy subjects. These 30 subjects were subsequently genotyped for their PEPT2 polymorphisms. Results  In total, ten common single nucleotide polymorphisms (SNPs) were detected in the three populations, forming two PEPT2 haplotypes. There were significant ethnic differences in PEPT2 haplotype distribution: the frequencies of the *1 and *2 alleles were 0.307 and 0.693 in the Chinese population, 0.495 and 0.505 in the Malay population and 0.729 and 0.271 in Asian Indian population, respectively. The C _max of cephalexin was significantly lower in the Chinese (29.80 ± 4.09 μg ml⁻¹) population than in the Asian Indian one (33.29 ± 4.97 μg ml⁻¹; P = 0.045). This difference could be explained by the higher average body weight of the Chinese population. There was no other significant difference in cephalexin pharmacokinetics between either ethnic or PEPT2 genotype groups. Conclusion   PEPT2 polymorphism distributions differ significantly between Chinese, Malay and Asian Indian populations. However, cephalexin pharmacokinetics is not meaningfully different between Chinese and Asian Indians. The association between the PEPT2 haplotype and cephalexin pharmacokinetics could not be confirmed, and future studies under better controlled conditions are needed.     

(<Emphasis Type="Italic">Z</Emphasis>)-3-Hexenyl diglycosides from <Emphasis Type="Italic">Spermacoce laevis</Emphasis> Roxb.

A new (Z)-3-hexenyl O-β-d-glucopyranosyl-(1→6)-β-d-glucopyranoside was isolated from the aerial part of Spermacoce laevis, along with 17 known compounds: (6S,9R)-roseoside, (Z)-3-hexenyl O-β-d-glucopyranoside, (Z)-3-hexenyl O-α-l-rhamnopyranosyl-(1→6)-β-d-glucopyranoside, (Z)-3-hexenyl O-α-l-arabinopyranosyl-(1→6)-β-d-glucopyranoside, phenyethyl O-β-d-glucopyranoside, phenyethyl O-α-l-arabinopyranosyl-(1→6)-β-d-glucopyranoside, phenyethyl O-α-l-rhamnopyranosyl-(1→6)-β-d-glucopyranoside, benzyl O-α-l-arabinopyranosyl-(1→6)-β-d-glucopyranoside, benzyl O-β-d-xylopyranosyl-(1→6)-β-d-glucopyranoside, asperuloside, 6α-hydroxyadoxoside, asperulosidic acid, kaempferol 3-O-β-d-glucopyranoside, kaempferol 3-O-rutinoside, quercetin 3-O-β-d-galactopyranoside, quercetin 3-O-α-l-rhamnopyranosyl-(1→6)-β-d-galactopyranoside, and rutin. The structure determinations were based on physical data and spectroscopic evidence.     

D<Subscript>2</Subscript> but not D<Subscript>1</Subscript> dopamine receptor stimulation augments brain signaling involving arachidonic acid in unanesthetized rats

Rationale and objectives Signal transduction involving the activation of phospholipase A₂ (PLA₂) to release arachidonic acid (AA) from membrane phospholipids, when coupled to dopamine D₁- and D₂-type receptors, can be imaged in rats having a chronic unilateral lesion of the substantia nigra. It is not known, however, if the signaling responses occur in the absence of a lesion. To determine this, we used our in vivo fatty acid method to measure signaling in response to D₁ and D₂ receptor agonists given acutely to unanesthetized rats. Methods [1-¹⁴C]AA was injected intravenously in unanesthetized rats, and incorporation coefficients k* for AA (brain radioactivity/integrated plasma radioactivity) were measured using quantitative autoradiography in 61 brain regions. The animals were administered i.v. the D₂ receptor agonist, quinpirole (1 mg kg⁻¹, i.v.), the D₁ receptor agonist SKF-38393 (5 mg kg⁻¹, i.v.), or vehicle/saline. Results Quinpirole increased k* significantly in multiple brain regions rich in D₂-type receptors, whereas SKF-38393 did not change k* significantly in any of the 61 regions examined. Conclusions In the intact rat brain, D₂ but not D₁ receptors are coupled to the activation of PLA₂ and the release of AA.     

A PET study on regional coexpression of 5-HT<Subscript>1A</Subscript> receptors and 5-HTT in the human brain

Rationale Several lines of evidence suggest inter-dependency between the serotonin transporter (5-HTT) and the 5HT_1A receptor, two recognised targets for the treatment of anxiety and depression. Objectives to examine the correlation of regional expression levels for these two serotonergic markers in the human brain in vivo. Methods Twelve male control subjects were examined with PET twice on the same day, using the radioligands [¹¹C]WAY 100635 and [¹¹C]MADAM for quantification of the 5-HT_1A receptor and the 5-HTT, respectively. The binding potential (BP) was calculated for raphe nuclei, hippocampus and frontal cortex. Results In all regions, the BP for both [¹¹C]WAY 100635 (raphe nuclei 1.85–4.71, hippocampus 2.52–6.17, frontal cortex 2.03–3.79) and [¹¹C]MADAM (2.70–7.65, 0.47–1.76, 0.18–0.51) varied several fold between subjects. In the raphe nuclei, where the two markers are situated on the same neurons, the ratio of [¹¹C]WAY 100635 binding to [¹¹C]MADAM BP binding varied considerably (0.43–1.05). There was a positive correlation between the two markers in the raphe nuclei (r _xy = 0.68, p < 0.05) and in the hippocampus (r _xy = 0.97, p < 0.001) but not in the frontal cortex (r _xy = −0.25, p = 0.44). Conclusions The results support a correlation between density levels of the 5-HT_1A-receptor and the 5-HTT in the raphe nuclei and hippocampus but not in the frontal cortex. A suggested clinical implication is that the inter-individual variability in 5-HT_1A-receptor and 5-HTT densities, as well as the ratio of these, is of particular interest in relation to individual responses to selective serotonin reuptake inhibitor treatment.     

Elevated prolactin responses to <Emphasis Type="SmallCaps">l</Emphasis>-tryptophan infusion in medication-free depressed patients

Rationale Several previous neuroendocrine studies have demonstrated reduced 5-HT_1A receptor function in major depressive disorder (MDD). However, hypercortisolaemia or previous drug treatment may have been significant confounds. Objectives To replicate previous studies in subjects with MDD who had been drug free for at least 8 weeks and to relate the findings to measures of HPA axis function. Methods Hormonal responses to l-tryptophan infusion were measured in patients with MDD (n=20) and healthy controls (n=20). Basal salivary cortisol and DHEA were also profiled. Results No attenuation of 5-HT_1A receptor-dependent neuroendocrine responses (growth hormone, prolactin) was observed in patients with MDD. The prolactin response to l-tryptophan was significantly greater in MDD patients than in healthy controls (P=0.008). There was a significant negative correlation between prolactin response and basal salivary cortisol secretion over the 3 days prior to the test. Conclusions These data do not support previous findings of reduced 5-HT_1A function in MDD and suggest that hypercortisolaemia or psychotropic medication may have accounted for the attenuation. Basal cortisol, DHEA and the cortisol-DHEA ratio did not differ between patients and controls, and all patients were psychotropic medication-free. The greater prolactin response to l-tryptophan infusion in depressed subjects may be the result of an increase in dopamine receptor sensitivity, secondary to reduced dopamine levels.