Box-Behnken设计-效应面法优化根皮素纳米结构脂质载体处方研究

目的： Box-Behnken设计-效应面法优化根皮素纳米结构脂质载体处方。方法： 乳化超声法制备根皮素纳米结构脂质载体，采用包封率（Y₁）和粒径（Y₂）作为考察指标，选择脂-药比（X₁）、固液脂质比（X₂）、表面活性剂浓度（X₃）为主要影响因素，通过二次多元回归模型拟合根皮素纳米结构脂质载体的影响因素与响应值之间的关系，绘制模型效应面图，并验证最佳处方。结果： 最佳处方为：脂-药比为16.4，固液脂质比为4.7，表面活性剂浓度为1.3%。所得3批根皮素纳米结构脂质载体包封率分别为85.7%、84.9%和85.1%；粒径分别为166.9 nm、168.4 nm和170.3 nm，与模型预测值接近。制备的根皮素纳米结构脂质载体基本外貌为圆形，无粘连现象。根皮素存在状态由结晶态转变为无定型态。体外释药具有明显的缓释特征，释药过程符合Weibull模型。结论： Box-Behnken实验设计可用于根皮素纳米结构脂质载体处方的筛选，为后续体内外研究奠定了基础。     

Voltammetric determination of vitamins in a pharmaceutical formulation

Direct current polarography and differential pulse polarographic methods have been developed for the qualitative as well as quantitative analysis of vitamin B₁, B₂ and B₆. Thiamin (Vitamin B₁) produced a well-defined wave in 0.1 M KCl at pH 5.2 with E_1/2=−1.2 V and E_p=−1.22 V versus saturated calomal electrode (SCE). Riboflavin (Vitamin B₂) gave two distinct waves in Britton Robinson buffer at pH 1.8 with E_1/2 VALUES=−0.13 and −0.34 V versus SCE and at pH 6.5 with E_1/2=−1.10 V and E_p=−1.2 V versus SCE. Pyridoxin (Vitamin B₆) produced a well-defined wave in Britton Robinson buffer at pH 6.5 with E_1/2=−1.7 V and E_p=−1.68 V versus SCE. All the three Vitamins under study are reversibly reduced at the electrode surface. The number of electrons involved in the electrode process for vitamin B₁ and B₆ is one in each case where as for the two waves of B₂ it is one and two, respectively. This has been confirmed by the measurement of E_3/4–E_1/4 values and also from the log plot slopes for the reduction waves. The wave height of polarogram was found to be proportional to the vitamin concentration. The developed methods have been standardised for the determination of these compounds in pharmaceutical formulation. The concentration of Vitamin B₁, B₂ and B₆ are found to be 9.96, 9.92 and 3.01 mg, respectively in 240 mg of capsule powder of a standard company (name has not been disclosed due to secrecy purpose). The results have been found to be in excellent agreement to that claimed by the manufacturer. The observed data has been subjected to statistical analysis, which revealed high reliability and precision.     

A comparison of matrix resolution method, ratio spectra derivative spectrophotometry and HPLC method for the determination of thiamine HCl and pyridoxine HCl in pharmaceutical preparation

A comparison of two spectrophotometric methods and a HPLC method were described in this work for the analysis of pyridoxine hydrochloride and thiamine hydrochloride in a vitamin combination. In the first method, A₁¹ (1%, 1 cm) values of these two compounds were calculated using absorbances measured at 246.8 and 290.5 nm in zero-order spectra. The matrix was written for A₁¹ (1%, l cm) values and the concentration of both compounds were determined using ‘Matlab’ software. In the second method, the measurements in the derivative of the ratio spectra were made at 297.8 and 309.5 nm for pyridoxine hydrochloride and at 245.6 and 257.7 nm for thiamine hydrochloride. The calibration graphs were established in the range 8–40 μg/ml of both vitamins. In the HPLC method, the separation of these compounds was realized on a Nucleosil 100-5 C₁₈ column with 0.1 M (NH₄)₂C0₃–water–methanol (5:15:80 v/v) as the mobile phase. Results of spectrophotometric and HPLC procedures were compared.     

Basal and activity-induced release of substance P from primary afferent fibres in NK1 receptor knockout mice: evidence for negative feedback

The concept that NK₁ receptors are located pre-junctionally on substance P (SP)-containing nerves, acting as autoreceptors to inhibit SP release, has been suggested, but remains a controversial issue. To further investigate the existence of this receptor on central and peripheral terminals of primary afferent fibres, NK₁ receptor knockout mice and an NK₁ receptor antagonist were used in nerve-attached tissue preparations. These were the isolated dorsal horn of the spinal cord with dorsal roots attached, and the hairy skin of the hind paw with attached saphenous nerve. The results reveal that in the dorsal horn preparation, basal release of SP is significantly higher in NK₁^−/− mice than NK₁^+/+ mice (P<0.05, n=7 mice/strain). However, a difference in SP release evoked in the dorsal horn by electrical stimulation of the dorsal roots or capsaicin application was not observed. In contrast, antidromic electrical stimulation of the saphenous nerve caused a substantially greater release of SP in the skin of NK₁^−/− mice than in NK₁^+/+ mice (P<0.05, n=5 to 6 mice/strain). These results provide evidence for the existence of NK₁ autoreceptors on sensory nerves in skin, which may be relevant to the modulation of their peripheral pathophysiological effector functions.     

An alternative method to the evaluation of similarity factor in dissolution testing

This paper addresses an alternative method to the evaluation of similarity factor f₂ as a criterion for assessment of similarity between two in-vitro dissolution profiles as proposed in the SUPAC-IR Guidance (1995). Diltiazem hydrochloride Sustained-Release (SR) tablets were tested and the following independent-model dissolution parameters were used: t_10% dissolution time, t_25% dissolution time, t_50% dissolution time, mean dissolution time (MDT), dissolution efficiency (DE) at t₁₂₀, and at t₃₆₀. To compare the dissolution profiles, several release models were tested such as Higuchi, zero order, first order, Baker-Lonsdale, Hixson-Crowell, Weibull and Korsmeyer-Peppas. The similarities between two in-vitro dissolution profiles were assessed by pair-wise independent-model procedures such as difference factor (f₁), similarity factor (f₂) and Rescigno index (ξ₁ and ξ₂). The in vitro release kinetics of diltiazem hydrochloride sustained release tablets were evaluated using USP apparatus 2.     

Nitric oxide modulates angiotensin II-induced endothelial vasoconstrictor prostanoid release

This study investigated the modulation of angiotensin II-induced endothelial prostanoid release in rabbit aortic rings. Two cumulative dose response curves with 90-min washing interval were performed. Incubation with l-N^G-nitroarginine methyl ester (l-NAME) 10^− 4 M increased angiotensin II maximal contractile response (E_max). This effect was reversed by indomethacin 10^− 5 M, diphenyliodinum 10^− 5 M, Tempol 10^− 5 M or ascorbic acid 10^− 4 M in both cumulative dose response curves and by SQ 29548 10^− 6 M in the second cumulative dose response curve. When segments were treated with tetraethylamonium 10^− 3 M but not with glibenclamide 10^− 5 M during the washing period, l-NAME recovered its ability to enhance the E_max in arteries incubated with SQ 29548. Conclusions: nitric oxide modulates angiotensin II-induced endothelial release of cyclooxygenase-dependent eicosanoids, one of which acts through thromboxane A₂/prostaglandin H₂ receptors and would decrease K_Ca channel activity. An increase in free radical production may account for the enhancement of such prostanoid release. Furthermore, it was found that in the present conditions, the release of the hyperpolarizing factor would improve in order to maintain the vascular tone.     

A preformulation study on the kinetics of HI-6 in concentrated solution

The degradation kinetics of HI-6 have been investigated at various temperatures and at different pHs at a concentration of 200 mg/ml. Both aqueous and other hydrophilic solvents (glycols and glycerol-water mixtures) have been used. The degradation of HI-6 follows pseudo-first-order kinetics with respect to HI-6. The observed rate seems to depend on a hydroxyl ion-catalyzed reaction (k_OH) and an un/water catalyzed reaction (k₀) which show influence at pH below 3. The pH profile shows a positive slope less than one, which seems to depend on an error in the determination of the rate constants at higher pH. k_OH was determined to be 1 · 10⁹ andk₀ to be 0 · 011 h⁻¹ at 60° C. The observed rate seems to be independent of the dielectric constant of the solvent. The activation energy k₀ has been determined to be 82.0 kJ mol⁻¹. Based upon these data the predicted shelf life (t_90%) at pH 0 will not be long than 13 days at 25 ° C and 9 months at 0°C. Thus, the systems studied seem to be unsuitable to formulate a stable intramuscular formulation of HI-6.     

右美托咪定对肺癌根治术患者围术期氧化应激反应及细胞免疫功能的影响

目的：观察右美托咪定对胸腔镜肺癌根治术患者围术期氧化应激反应及免疫功能的影响。方法：全麻单肺通气行胸腔镜肺癌根治术患者100例;随机分为右美托咪定组（A组）和对照组（B组）,每组50例。A组麻醉诱导前20 min静注右美托咪定负荷量1 μg·kg^-1,15 min输完,随后给予维持量0.5 μg ·kg^-1 ·h^-1,手术结束前20 min时停药;B组相同方法输注等量生理盐水;在T₀（麻醉诱导前30 min）、T₁（完成手术时）、T₂（手术后12 h）、T₃（手术后24 h）时采集静脉血,检测丙二醛（MDA）浓度和超氧化物歧化酶（SOD）的水平,并分别测定CD₃⁺、CD₄⁺、CD₈⁺的表达水平和NK细胞的含量,计算CD₄⁺/CD₈⁺比值。结果：与T₀相比,T₁-T₃时间点两组血清SOD活性降低,MDA浓度升高（P<0.05）;CD₃⁺、CD₄⁺含量以及CD₄⁺/CD₈⁺比值、NK细胞水平均降低（P<0.05）。2组比较,T₁-T₃时间点A组血清SOD活性升高、MDA浓度降低得更明显（P<0.05）。B组CD₃⁺、CD₄⁺含量以及CD₄⁺/CD₈⁺比值、NK细胞水平降低得更显著（P<0.05）。结论：右美托咪定能够有效抑制围手术期诱发的应激反应,减轻胸腔镜肺癌根治术后患者的免疫抑制。     

Stimulus-evoked glutamate release is diminished by acute exposure to uranium in vitro

Uranium is used in civilian applications, in the manufacture of nuclear fuel, and by the military for munitions and armament, but little information is available on its neurotoxicity. Neurological dysfunctions have been observed after chronic exposure in both animals and humans, but the actions of acute exposure on amino acid neurotransmission have not been investigated. The following study was performed to examine the effects of uranyl ion (UO₂^+ 2) on hippocampal glutamatergic and GABAergic function as possible bases for the neurotoxicity and to assess the direct effects on the exocytotic process. Nominal UO₂^+ 2 concentrations were applied to superfused hippocampal synaptosomes to permit estimation of the metal's potency on endogenous transmitter release in the presence and absence of Ca^+ 2. K⁺-evoked glutamate release was diminished in the range of 10 nM–316 μM UO₂^+ 2, resulting in an IC₅₀ of 1.92 μM. In contrast, the potency of UO₂^+ 2 to decrease stimulated GABA release was reduced, producing an IC₅₀ ≈ 2.6 mM. In the absence of Ca^+ 2 in the superfusion medium there was no systematic change in the magnitude of glutamate or GABA release, suggesting that UO₂^+ 2 does not possess Ca^+ 2-mimetic properties. The inhibitory potency of UO₂^+ 2 on glutamate release is similar to the potencies of other multivalent metal ions, suggesting by inference an action exerted on voltage-sensitive Ca^+ 2 channels. The bases for the reduced potency to inhibit GABA release is not known, but differential sensitivity to other heavy metals has been reported for glutamate and GABA neurotransmission. These findings indicate a profile of neurotoxicity not unlike that of other metal ions, and indicate the importance of extending subsequent studies to chronic exposure models.     

Solution and solid state properties of a set of procaine and procainamide derivatives

A set of potential Class III antiarrhythmic agents of structure p-HOOC–R–CO–NH–C₆H₄–CO–X–C₂H₅–N(C₂H₅)₂ were isolated as crystalline solids of the amide and ester derivatives, I: succinylprocainamide (X=–NH–, R=–C₂H₄–); II: succinylprocaine (X=–O–, R=–C₂H₄–); III: maleylprocainamide (X=–NH–, R=–C₂H₂–) and IV: maleylprocaine (X=–O–, R=–C₂H₂–). Although compounds I–IV exhibit similar solution properties (i.e. acid–base speciation, with zwitterionic (+−) to neutral (00) form ratios higher than 10⁴), aqueous solubility of –NH– derivatives is significantly higher than that of –O– derivatives and also, solvent effects on solubility (i.e. the change of water by ethanol) is clearly different in both series. Solution and solid-state properties of I–IV were characterized to account for the observed differences. Results indicate that procainamide derivatives I and III crystallizes as (+−)_s but procaine derivatives II and IV as (00)_s. Besides, I is anhydrous but II–IV are hydrates. Aqueous solubility and solvent effect on solubility are controlled by the intrinsic solubility of the species (+−) in I and III and (00) in II and IV. The rise of hydrophilicity of species (00) due to the structural change from –O– to –NH– would determine the change in the structure of the precipitating crystals from (00)_s to (+−)_s. Solid structure (zwitterionic or neutral), as well as composition (anhydrous or hydrated) may be recognized as the main factors in determining the rank of aqueous solubility of the set: (+−)>(+−·H₂O)>(00·H₂O).     

Comparative study of the effects of salinomycin and monensin on electrophysiologic and contractile properties of canine myocardium

The effects of the monocarboxylic ionophore, salinomycin (K⁺-selective), on isometric twitcches, high K⁺-induced contracture and transmembrane action potentials were compared with those of the monocarboxylic ionophore, monensin (Na⁺-selective), in isolated canine right ventricular muscle. In a concentration (5 × 10⁻⁶) which did not produce changes in resting force, salinomycin increased peak active force ( P₀, + 170 ± 36%, mean % change from control ±S.D., P< 0.01). and relaxation and maximal rates of force development (dP/dt_max, + 123 ± 33%, P < 0.01) and relaxation (−dP/dt_max, + 180 ± 40%, P < 0.01) of the isometric twitch. A similar response pattern was found for 5 × 10⁻⁶ M monensin (P₀, + 90 ± 24%, P < 0.01; dP/dt_max, + 137 ± 19%, P < 0.01; −dP/dt_max, + 145 ± 20%, P < 0.01). In contrast to their effects on isometric twitches, salinomycin reduced peak K⁺ contracture force (P_c, −35 ± 14%, P < 0.01) whereas monensin increased it (P_c, +30 ± 12%, P < 0.02). Ventricular muscle action potential duration was shortened similarly by the ionophores. β-Adrenergic receptor blockade with nadolol diminished salinomycin's effects on the isometric twitch and K⁺ contracture, but not its effect to shorten the action potential. Monensin's actions were unaffected by nadolol. These results suggest that salinomycin's effects arise from both a direct modulation of K⁺ movement and the release of endogenous catecholamine. In contrast, monensin may act to alter intracellular Na⁺ which in turn leads to Na⁺---Ca²⁺ exchange and Ca²⁺ -mediated modulation of K⁺ movement.     

Mechanisms of vasoinhibitory effect of cardioprotective agent, CP-060S, in rat aorta

Vasoinhibitory effects of (−)-(S)-2-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-3-[3-[N-methyl-N-[2-(3,4-methylenedioxyphenoxy)ethyl]amino]propyl]-1,3-thiazolidin-4-one hydrogen fumarate (CP-060S), a synthesized cardioprotective agent, were examined. In the rat aortic rings, the contractile responses to cumulative application of angiotensin II, [Arg⁸]-vasopressin (vasopressin), or prostaglandin F₂ were inhibited by CP-060S in a concentration-dependent manner. The Ca²⁺-induced contractions in the presence of vasopressin or prostaglandin F₂ were also inhibited by CP-060S in a concentration-dependent manner. The inhibitory effect of 10⁻⁵ M CP-060S on phenylephrine-induced contraction was as potent as that of 10⁻⁶ M nifedipine, and the combined addition of 10⁻⁶ M nifedipine and 10⁻⁵ M CP-060S showed the effect similar to that of 10⁻⁵ M CP-060S alone. In rat aorta loaded with a Ca²⁺ indicator, fura-PE3, 10⁻⁵ M CP-060S completely inhibited the high K⁺-induced increase in cytosolic Ca²⁺ level ([Ca²⁺]_i) and contraction. In contrast, 10⁻⁵ M CP-060S only partially inhibited the increase in [Ca²⁺]_i and contraction due to phenylephrine or prostaglandin F₂. In the presence of 10⁻⁶ M nifedipine, 10⁻⁵ M CP-060S did not inhibit the increase in [Ca²⁺]_i and contraction induced by prostaglandin F₂. In a Ca²⁺-free medium, the phasic increases in contraction and [Ca²⁺]_i induced by phenylephrine were not affected by 10⁻⁵ M CP-060S. These results suggest that the vasoinhibitory effect of CP-060S in rat aortic rings is due mainly to the inhibition of L-type voltage-dependent Ca²⁺-channels.     

基于Notch/Snail信号的艳山姜挥发油对内皮间质转分化的保护作用研究

目的：探讨艳山姜挥发油对转化生长因子β₁（TGF-β₁）诱导的内皮间质转分化（EndMT）的干预作用及信号机制。方法：以10 ng·mL^-1 TGF-β₁诱导人脐静脉内皮细胞（HUVECs）建立EndMT模型。实验共分为两个部分：（1）分组：正常组,模型组（10 ng·mL^-1 TGF-β₁）,EOFAZ低剂量组（10 ng·mL^-1 TGF-β₁+1 μg·L^-1 EOFAZ）,EOFAZ高剂量组（10 ng·mL^-1 TGF-β₁+4 μg·L^-1 EOFAZ）。EOFAZ干预作用2 h后加入TGF-β₁共同孵育72 h。采用Transwell小室实验检测细胞迁移能力;波形蛋白（Vimentin）和血小板-内皮细胞粘附分子（CD31）以及Notch-1的蛋白表达情况通过蛋白免疫印迹法检测。（2）分组：正常组,模型组（10 ng·mL^-1 TGF-β₁）,γ-分泌酶抑制剂组（10 ng·mL^-1 TGF-β₁+15 μmol·L^-1 DAPT）,EOFAZ高剂量组（10 ng·mL^-1 TGF-β₁+4 μg·L^-1 EOFAZ）。DAPT及EOFAZ干预作用2 h后加入TGF-β₁共同孵育72 h。通过蛋白免疫印迹法检测Notch-1,Snail和Slug的表达。结果：内皮细胞经TGF-β₁处理72 h后,细胞迁移能力明显增强（P<0.01）,CD31蛋白表达水平显著降低（P<0.01）,Vimentin,Notch-1,Snail和Slug蛋白表达水平显著提高（P<0.01,P<0.05）,给予EOFAZ作用后能逆转上述改变。同时在给予DAPT阻断Notch信号后,Notch-1,Snail和Slug蛋白水平下降（P<0.05）。结论：EOFAZ干预TGF-β₁诱导EndMT的作用与Notch信号相关,其可以进一步调控Snail和Slug的表达。     

Uptake and transport of the ACE-inhibitor ceronapril (SQ 29852) by monolayers of human intestinal absorptive (Caco-2) cells in vitro

The angiotensin-converting enzyme (ACE)-inhibitor ceronapril (SQ 29852) is shown to be a substrate of the intestinal dipeptide transporter. Uptake by Caco-2 cells, grown as confluent monolayers, follows a major saturable pathway (K_m, 0.91 ± 0.11 mM; 90% at 1 mM) together with a minor passive component (k_J, 32.3 ± 6.6 ng (10⁶ cells)⁻¹ (20 min)⁻¹. Uptake was inhibited by competition with dipeptides such as l-AIa-l-Pro (K_i, 2.96 mM) and l-Phe-Gly (K_i, 3.84 mM) but not by cephalosporins such as cephalexin. In contrast, transport was non-saturable, flux increased linearly with concentration and data were consistent with a passive transepithelial transport mechanism. Transport profiles showed a biphasic dependence upon time with an initial flux of 0.83 ± 0.02 ng insert⁻¹ min⁻¹ (k₁) and a terminal value of 1.65 ± 0.08 ng insert⁻¹ min⁻¹ ((k₂) at 100 μM. It is concluded that the basolateral efflux is retarded so that the passive paracellular transport controls the overall transepithelial transport characteristics in the Caco-2 model. Carrier-mediated uptake into intestinal enterocytres, followed by rate-limiting basolateral efflux, may explain the extended t_max in vivo following oral administration.     

Pluronic gels for nasal delivery of Vitamin B12. Part I: preformulation study

Thermoreversible nasal gels of Vitamin B₁₂ using pluronic PF 127 were aimed to improve absorption and patient compliance. In the present research work, effects of Vitamin B₁₂ and gel additives, viz. PF concentration, osmolarity, polyethylene glycol (PEG 15000) on thermodynamic properties of phase transitions at gelation (T₁) and gel melting (T₂) is reported. Aqueous PF 127 gels prepared by cold method containing pluronic (20–24%, w/w), vitamin, sorbitol, PEG, and benzalkonium chloride. T₁ decreases and T₂ increases with vitamin and PF concentration. Gelation range narrows with sorbitol and PEG. Suppression of T₂ is significantly higher than T₁ with both the additives. The linearity was observed only for semilogarithmic plot of PF concentration and 1/T₂ for sorbitol and PEG, which reveals significant interaction of both at gel melting. Enthalpy of both transitions remains unchanged with vitamin indicating no interaction with polymer. Benzalkonium chloride decreased gelation onset temperature. Thermodynamic properties of PF 127 gels are significantly altered with polymer concentration and water-soluble formulation additives.     

Presynaptically acting snake venom phospholipase A2 enzymes attack unique substrates

Synaptosomes were incubated with bovine serum albumin (BSA) to examine whether the presynaptic action of snake venom phospholipase A₂ (PLA₂) toxins is due either to the release of fatty acids resistant to extraction by BSA or to the liberation of a specific fatty acid type. In the presence of BSA (0.5% or 1.0%) two PLA₂ enzymes from Naja naja atra and Naja naja kaouthia snake venoms that do not have a predominant presynaptic action at the neuromuscular junction (PS−) did not stimulate acetylcholine (ACh) release from synaptosomes. In contrast, two PLA₂ enzymes (β-bungarotoxin, scutoxin) that do have a predominant presynaptic action at the neuromuscular junction (PS+) did stimulate ACh release. BSA did not antagonize PS− enzymes by more efficiently extracting the fatty acids produced by these enzymes relative to PS+ enzymes. While absolute amounts of total and unsaturated fatty acid produced overlapped for the PS− and PS+ enzymes, the two PS+ enzymes produced a significantly greater absolute amount and relative percentage of palmitic acid (16:0) than did either of the PS− enzymes. However, the levels of free palmitic acid remaining in the synaptosomes where they would exert effects on ACh release were similar for the N. n. kaouthia PLA₂ (PS−) and β-bungarotoxin (PS+). Therefore, the total (supernatant plus synaptosomal) amount of palmitic acid produced per se did not account for stimulation of ACh release, since the greater amounts produced by the PS+ enzymes were removed from the synaptosomes by BSA. The production of higher levels of palmitic acid suggests either that PS+ enzymes gain access to sites containing phospholipid substrates unavailable to the PS− enzymes, or that they have a different substrate preference. These findings suggest new possibilities for the mechanism of PS + PLA₂ action, including site-directed enzymatic activity and protein acylation.     

Evaluation of the role of nicotinic acetylcholine receptor subtypes and cannabinoid system in the discriminative stimulus effects of nicotine in rats

Male Wistar rats were trained to discriminate (−)-nicotine (0.4 mg/kg) from saline under a two-lever, fixed-ratio 10 schedule of water reinforcement. During test sessions the following drugs were coadministered with saline (substitution studies) or nicotine (0.025–0.4 mg/kg; combination studies): the ₄β₂ nicotinic acetylcholine receptor subtype antagonist dihydro-β-erythroidine (DHβE), the non-selective nicotinic acetylcholine receptor subtype antagonist mecamylamine, the ₇ nicotinic acetylcholine receptor subtype antagonist methyllycaconitine (MLA), the ₄β₂ nicotinic acetylcholine receptor subtype agonist 5-iodo-3-(2(S)-azetidinylmethoxy)pyridine (5-IA), the cannabinoid CB₁ receptor antagonist/partial agonist rimonabant, the cannabinoid CB₂ receptor antagonist N-[(1S)-endo-1,3,3-trimethylbicyclo-[2.2.1]heptan-2-yl]5-(4-chloro-3-methyl-phenyl)-1-(4-methybenzyl)pyrazole-3-carboxamide (SR 144528), the cannabinoid CB_1/2 receptor agonists (−)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)-phenyl]-trans-4-(3-hydroxy-propyl)cyclohexanol (CP 55,940) or R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]-pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-(1-naphthalenyl)-methanone mesylate (WIN 55,212-2), the endogenous cannabinoid agonist and non-competitive ₇ nicotinic acetylcholine receptor subtype antagonist anandamide, the anandamide uptake and fatty acid amide hydrolase inhibitor N-(4-hydroxyphenyl)-5Z,8Z,11Z,14Z-eicosatetraenamide (AM-404), the fatty acid amide hydrolase inhibitor cyclohexylcarbamic acid 3′-carbamoyl-biphenyl-3-yl ester (URB 597), AM-404 + anandamide or URB 597 + anandamide. 5-IA (0.01 mg/kg) fully substituted for nicotine, while other drugs were inactive. In combination studies, DHβE and mecamylamine dose-dependently attenuated the discriminative stimulus effects of nicotine and the full substitution of 5-IA, while MLA, rimonabant, SR 144528, CP 55,940, WIN 55,212-2, and URB 597 did not alter the nicotine cue. Pretreatment with AM-404 + anandamide or URB 597 + anandamide weakly enhanced nicotine-lever responding. Our pharmacological analyses demonstrates that the expression of nicotine discrimination is under the control of nicotinic acetylcholine receptor subtypes composed of ₄β₂ (but not of ₇) subunits. Furthermore, we excluded the involvement of either cannabinoid CB₁ and CB₂ receptors or increases in the endocannabinoid tone in the nicotine discrimination.     

Effects of Fe on ion channels: Na channel, delayed rectified and transient outward K channels

The effects of Fe²⁺ on the properties of three types of ion channels were studied in acutely dissociated rat hippocampal pyramidal neurons from area CA1 at postnatal ages of 7–14 days using the whole cell patch clamp technique. The results indicated that: (1) in the existence of Fe²⁺, the activation voltage threshold of transient outward K⁺ currents (I_A) was decreased. The normalized current-voltage curves of activation were well fitted with a single Boltzmann function, and the V_1/2 was 2.44±1.14 mV (n=15) in control, whereas 1.79±1.53 (n=15), −2.96±0.92 (n=14), −5.11±1.31 (n=13), −9.05±1.64 mV (n=12) in 1, 10, 100 and 1000 μ Fe²⁺, respectively. Differences between two groups were significant (P<0.05, n=12–15), except for that between the control and 1 μ (P>0.05, n=15). (2) Fe²⁺ caused a left shift of the current–voltage curves of steady-state inactivation of I_A in a concentration-dependent manner. The curves were well fitted with a single Boltzmann function with similar slope (P>0.05, n=10–13). The V_1/2 were −70.71±1.23 (n=13), −71.14±1.37 (n=13), −78.21±1.17 (n=11), −84.61±1.34 (n=12), and −89.68±2.59 mV (n=10) in control, 1, 10, 100 and 1000 μ Fe²⁺, respectively. Fe²⁺ also shifted the current–voltage curves of Na⁺ channel steady-state inactivation to more negative depolarization potentials in parallel, with V_1/2, −67.37±1.33 mV (n=12) in control, and −67.52±1.28 mV (n=12), −68.24±1.61 mV (n=10), −71.58±1.45 mV (n=10), −76.65±1.76 mV (n=9) in 1, 10, 100 and 1000 μ Fe²⁺ solutions, respectively. (3) In Fe²⁺ solutions, the recovery from inactivation of I_A was slowed. (4) With application of different concentrations of Fe²⁺, the voltage threshold of activation of delayed rectified outward K⁺ currents (I_K) was decreased, while Fe²⁺ showed a little inhibition at more positive depolarization. Briefly, the results demonstrated that Fe²⁺ is a dose- and voltage-dependent, reversible modulator of I_A, I_K and Na⁺ channels. The results will be helpful to explain the mechanism of Fe²⁺ physiological function and Fe²⁺ intoxication in the central nervous system.     

Direct enantioselective determination of (R)- and (S)-propranolol in human plasma. Application to pharmacokinetic studies

In order to examine possible drug interactions of (R)- and (S)-propranolol a randomized, double blind crossover study has been performed, administering orally single doses of 40 mg (R,S)- and of 20 mg (S)-propranolol.HCl three times daily over a week to reach steady state conditions. After the first single dose of 40 mg (R,S)-propranolol.HCl, the AUC_o−t8 and C_max values of the (S)-isomer were greater than those of the (R)-isomer: the ratio of AUC_(s) over AUC_(R) was 1.77 (P < 0.05) and that of C_max 1.57 (P < 0.01). When (S)-propranolol.HCl was given as a single 20 mg dose, the AUC_(s) value was a factor of 0.55 lower than after administration of 40 mg (R,S)-propranolol.HCl. At steady state, the AUC of (S)-propranolol was 1.52 times higher (P < 0.01) than that of the (R)-isomer after administration of 40 mg racemate, and comparing the (S)-isomer, the ratio was 1.21. Following administration of the first single dose of 40 mg of the racemate, the mean (SD) clearance of the (R)- and (S)-isomers was 110 (84) and 61 (37) ml min⁻¹ kg⁻¹, respectively; at steady state these values were 89 (55) and 57 (37) ml min⁻¹ kg⁻¹, respectively. Respective values for (S)-propranolol after single isomer administration (20 mg) were 86 (36) and 57 (25) ml min⁻¹ kg⁻¹ in single dose and steady state situations. The data are based on the quantitative analysis of (R)- and (S)-propranolol in plasma. A sensitive enantioselective LC-bioassay based on the formation of the (R)- and (S)-propranolol-oxazolidine-2-one and resolution of these derivatives on a (R,R)-dinitrobenzoyl-diaminocyclohexane ((R,R)-DNB-DACH) chiral stationary phase was developed, using dichloromethane—methanol (99.75:0.25, v/v) as mobile phase, with fluorimetric detection.     

Disposition kinetics and urinary excretion of levofloxacin on concomitant administration with meloxicam in cross-bred calves

The disposition kinetics and urinary excretion study of levofloxacin was conducted in 5 male cross-bred calves following its single intravenous administration (4 mg kg⁻¹) concurrently with meloxicam (0.5 mg kg⁻¹). Levofloxacin was estimated by microbiological assay. The drug levels above MIC₉₀ in plasma, were detected up to 10 h. Disposition kinetic parameters were calculated by two-compartment open model. Rapid distribution of levofloxacin was evidenced by a small distribution half-life (0.13 ± 0.01 h) and high K₁₂/K₂₁ ratio (2.21 ± 0.15). High ratio of AUC/MIC (90.2 ± 3.41) indicated good antibacterial activity of levofloxacin. The AUC, Vd_area, elimination half-life, MRT and total body clearance were 9.02 ± 0.34 μg ml⁻¹ h, 1.38 ± 0.05 l kg⁻1, 2.16 ± 0.08 h, 2.58 ± 0.11 h and 0.45 ± 0.02 l kg⁻¹ h⁻¹, respectively. About 38.4% of the administered dose of levofloxacin was excreted in urine within 24 h. A suitable intravenous dosage regimen for levofloxacin would be 1.8 mg kg⁻¹ repeated at 8 h intervals when prescribed with meloxicam in calves.