An analysis of the B-adrenergic action of oxyfedrine

1-3-methoxy-ω-(1-hydroxy-1-phenylisopropylamino)-propiophenone hydrochloride (oxyfedrine) (10^?8–10^?6 g/ml) produces a positive inotropic effect on electrically driven guinea-pig left atria which is prevented by propranolol; higher concentrations depress contractile force. Oxyfedrine (10^?8–10^?6 g/ml) effectively antagonizes the action of isoprenaline but not that of theophylline ethylenediamine. Oxyfedrine (10^?5 g/ml)-induced relaxation of the guinea-pig tracheal chain is not reversed by repeated washing but is antagonized by propranolol (10^?7 g/ml). The relaxed tracheal chain contracts when an additional dose of oxyfedrine (10^?5 g/ml) or quinidine (10^?5 g/ml) was administered. The oxyfedrine-induced contraction is relaxed by papaverine (5 × 10^?6 g/ml), theophylline ethylene-diamine (10^?5 g/ml) or adenosine (5 × 10^?5 g/ml) but not by isoprenaline (2 × 10^?8 g/ml) or adrenaline (10^?7 g/ml) nor is it prevented by dibenamine (10^?5 g/ml), methysergide (10^?6 g/ml), atropine (10^?5 g/ml) or tripelennamine (10^?7 g/ml). These observations suggest that oxyfedrine interacts with the ß-adrenergic receptor, inducing at adequate concentrations, stimulation and blockade to catecholamines simultaneously; in this interaction, higher concentrations of oxyfedrine produces a direct depression (quinidine-like) of cardiac muscle and a contraction of tracheal muscle.     

Effect of Dopexamine Hydrochloride on Sympathetic Neuroeffector Transmission in Rabbit Isolated Pulmonary Artery

Abstract: The effects of dopexamine hydrochloride on sympathetic neuroeffector transmission were studied in rabbit isolated pulmonary artery. Short-term exposure of dopexamine (10-⁸x10^-7 M) and cocaine (10^-6-3x10^-5 M), but not desipramine (3x10^-9-3x10^-7 M), to the artery enhanced the contractions evoked by electrical-field stimulation. Corticosterone (4x10^-5 M), corticosterone (4x10^-5 M) plus cocaine (3x10^-8 M), but not cocaine (3x10^-5 M), attenuated the enhancement seen with dopexamine. High concentrations of dopexamine (10^-5-3x10^-5 M), cocaine (10^-4 M), and desipramine (10^-6-10^-5M) decreased the stimulation-evoked contractions. Dopexamine (10^-7-3x10^-5 M), but neither cocaine nor desipramine, caused an increase in resting tension that waned with time. Corticosterone (4x10^-5 M), but not cocaine (3x10^-5 M), attenuated the increase in resting tension. Propranolol (10^-6 M) did not alter the enhancing and inhibitory effects of dopexamine. A single concentration (10^-7 and 10^-6 M) of either dopexamine or desipramine caused a time-dependent biphasic response as regards the repetitive stimulation-evoked contractions of pulmonary artery: initial enhancement followed by inhibition. The inhibitory effect of dopexamine (10^-6 M) and desipramine (3x10^-6 M) seen after prolonged exposure was almost irreversible and partially reversible, respectively, by washing the preparations with drug-free salt solution. Cocaine caused a monophasic steady-state response: either enhancement (10^-5 M) or inhibition (2x10^-4 M). In both cases, the onset was rapid. The reduction caused by cocaine (2x10^-4 M) and by prazosin (10^-9 M) was fully reversed. Dopexamine (10^-5 M) antagonized competitively the contractions evoked by noradrenaline (3x10^-9-10^-4 M). It is concluded that (1) the dopexamine-induced enhancement of neurogenic contractions is not due to either inhibition of neuronal and extraneuronal uptake of noradrenaline or an agonist action on prejunctional β₂-adrenoceptors; (2) that the dopexamine-induced inhibition of stimulation-evoked contraction is due to an inhibition of postjunctional α₁-adrenoceptors; and (3) that the dopexamine-induced increase in resting tension is due to its metabolite methyldopexamine.     

Dopamine-induced inhibition of synaptic transmission in lumbar paravertebral ganglia of the dog

Summary Dopamine, injected into the lumbar aorta in doses which produce a neurogenic vasodilatation in the isolated perfused hindleg of the dog (0.5–64×10^–8 moles), provokes a reversible inhibitory of the synaptic transmission in the paravertebral lumbar ganglia. This inhibitory effect is mimicked by epinine (1–64×10^–8 moles) and apomorphine (0.6–38.4×10^–8 moles) and is preferentially blocked by haloperidol (0.26×10^–6 moles), pimozide (2.2×10^–6 moles) and aceperone (2.5×10^–6 moles). (-)-Noradrenaline (0.6–19.2×10^–8 moles) is equipotent with dopamine in inhibiting ganglionic transmission; this noradrenaline inhibitory effect is preferentially blocked by phentolamine (8×10^–6 moles).The possibility that the dopamine-induced ganglionic inhibition is mediated via specific dopamine receptors is discussed.This work was aided by grants from the Coordination Committee for Scientific Research (C.C.A.S.) and from the Fund for Interdisciplinary Research, Belgium.     

NAT10 promotes cell proliferation by acetylating CEP170 mRNA to enhance translation efficiency in multiple myeloma

Multiple myeloma (MM) is still an incurable hematologic malignancy, which is eagerly to the discovery of novel therapeutic targets and methods. N-acetyltransferase 10 (NAT10) is the first reported regulator of mRNA acetylation that is activated in many cancers. However, the function of NAT10 in MM remains unclear. We found significant upregulation of NAT10 in MM patients compared to normal plasma cells, which was also highly correlated with MM poor outcome. Further enforced NAT10 expression promoted MM growth in vitro and in vivo, while knockdown of NAT10 reversed those effects. The correlation analysis of acetylated RNA immunoprecipitation sequencing (acRIP-seq) and ribosome profiling sequencing (Ribo-seq) combined with RIP-PCR tests identified centrosomal protein 170 (CEP170) as an important downstream target of NAT10. Interfering CEP170 expression in NAT10-OE cells attenuated the acceleration of cellular growth caused by elevated NAT10. Moreover, CEP170 overexpression promoted cellular proliferation and chromosomal instability (CIN) in MM. Intriguingly, remodelin, a selective NAT10 inhibitor, suppressed MM cellular growth, induced cellular apoptosis in vitro and prolonged the survival of 5TMM3VT mice in vivo. Collectively, our data indicate that NAT10 acetylates CEP170 mRNA to enhance CEP170 translation efficiency, which suggests that NAT10 may serve as a promising therapeutic target in MM.     

Effect of coenzyme Q10 on cutaneous healing in skin-incised mice

Coenzyme Q10 (CoQ10) is a biosynthesized quinone with 10 isoprene side chains in humans. To investigate the anti-inflammatory and wound healing effect of CoQ10, we performed in vivo and in vitro experiments. In vivo studies, there were 3 groups; Naive (without skin incision), Control (with skin incision) and CoQ10 (100 mg/kg treatment with skin incision). Collagen-like polymer (CLP) level of CoQ10 group was increased significantly compared to the control group (p<0.05). Also, CoQ10 group showed significant inhibition on myeloperoxidase (MPO) and PLA₂ level compared to the control group (p<0.05). These data show that CoQ10 may have an anti-inflammatory and a wound healing effect. CoQ10 showed significant antioxidant activity in vivo on malondialdehyde (MDA) and superoxide dismutase (SOD) levels compared to the control group (p<0.05). Although CoQ10 did not show antioxidant activity in cell free system of DPPH radical scavenge, it had a potent antioxidant activity in cell culture system of both silica- and zymosan-induced reactive oxygen species generation using Raw 264.7 cells. This result may be associated with the conversion of CoQ10 to the reduced form (CoQ10H₂) in the presence of some kinds of intracellular reducing agents. In conclusion, it is considered that CoQ10 appears to have a cutaneous healing effect in vivo, which may be related to the secondary action of CoQ10.     

Inhibition by (−)-Deprenyl of Agonist-Evoked Contractions in Rabbit Aorta

Abstract: The effect of (?)-deprenyl, a relatively selective MAO-B inhibitor, was examined for its ability to inhibit the contractions of rabbit isolated aorta evoked by various agonists and potassium. (?)-Deprenyl (10^?5?3 × 10^?4 M) antagonized the contractions evoked by noradrenaline (10^?8?3 × 10^?4 M); pA₂: 5.10. The antagonism was reversible. It was attenuated by cocaine (3x M); pA₂: 4.38, unchanged by corticosterone (4 × 10^?5 M); pA₂ 4.79 and enhanced by cocaine (3 × 10^?5 M) plus corticosterone (4 × 10^?5 M); pA₂: 5.48. (+)-Deprenyl (10^?6?10^?4 M) did not alter the contractions evoked by noradrenaline (3 × 10^?9?10^?4 M). Clorgyline (10^?5 and 10^?4 M) antagonized the noradrenaline-evoked contractions. Pargyline (10^?4 and 3 × 10^?4 M) had no effect. (?)-Deprenyl (10^?5?3 × 10^?4 M) antagonized the contractions evoked by phenylephrine (10^?8?10^?4 M); pA₂: 5.10. Removal of the endothelium did not alter the antagonism; pA₂: 5.35. (?)-Deprenyl (10^?5?3 × 10^?4 M) antagonized the contractions evoked by either 5-hydroxytryptamine (3 × 10^?8?3 × 10^?4 M); pA₂: 4.61 or by histamine (10^?6?3 × 10^?2 M); pA₂: 4.84. (?)-Deprenyl (3 × 10^?4 M) caused a non-competitive antagonism of the contractions evoked by potassium (1.5-5.5 × 10^?2 M). It is concluded that (?)-deprenyl is a weak inhibitor of postjunctional α-adrenoceptors, 5-hydroxytryptamine (5-HT₂) receptors, and histamine (H₁) receptors.     

Role of Cyclic AMP in Stimulation-Evoked Release of 3H-Noradrenaline from Rabbit Isolated Ear Artery

Abstract: The possible involvement of cyclic AMP in the stimulation-evoked ³H-overflow from rabbit isolated ear artery preloaded with ³H-noradrenaline was studied. Cyclic AMP (10^–5–3x10^–4M), 8–bromo-cyclic AMP (3x10^–4M) and adenosine (10^–5–3X10^–4M) enhanced stimulation-evoked ³H-overflow. Dibutyryl-cyclic AMP (10^–5–3x10^–4M) had no effect. Theophylline (3X10^–5M) and the phosphodiesterase inhibitor AH 21–132 (3X10^–5M) did not alter the enhancement of ³H-overflow caused by either cyclic AMP or adenosine. Forskolin (3X10^–6M) and the phosphodiesterase inhibitors ICI 63 197 (10^–4M) and AH 21–132 (3x10^–6–3x10^–5M) increased stimulation-evoked ³H-overflow. Forskolin (10^–6M) enhanced the effect of ICI 63 197 (3x10^–5M) but it did not alter the effect of AH 21–132. It is concluded that cyclic AMP is involved in the stimulation-evoked release of noradrenaline from postganglionic sympathetic nerves in the rabbit ear artery.     

Effects of pyroxamidine and guanethidine on contractile responses to field stimulation and to noradrenaline in the anococcygeus muscle and vas deferens of the rat

The effects of pyroxamidine (EMD 21192) and guanethidine on contractile responses were studied in the anococcygeus muscle and vas deferens of the rat. Pyroxamidine (10^?6 and 10^?5 M) and guanethidine (6 times 10^?6 and 10^?5 M) potentiated the responses to low concentrations of acetylcholine in the rat anococcygeus muscle. Following incubation of the muscle with 6-hydroxydopamine (10^?3M for 3 h), pyroxamidine (10^?5 M) and guanethidine (10^?5 M) had no effect on responses to acetylcholine. This suggests that the potentiating effect of pyroxamidine and guanethidine on responses to acetylcholine is due to the release of subthreshold concentrations of noradrenaline. In the anococcygeus, pyroxamidine (10^?6 and 10^?5 M) and guanethidine (10^?6 and 10^?5 M) inhibited responses to field stimulation and potentiated responses to exogenously applied (?)-noradrenaline. The responses to field stimulation in the vas deferens were also inhibited by 10^?5M pyroxamidine and by 10^?5 M guanethidine. 10^?6 M guanethidine, but not 10^?5 M pyroxamidine, potentiated responses to (?)-noradrenaline in the vas deferens. In the presence of nortriptyline (10^?6 M), a potent inhibitor of neuronal uptake, the inhibitory effects of pyroxamidine and guanethidine on responses to field stimulation were reduced or reversed and these drugs had no effect on responses to (?)-noradrenaline. This suggests that pyroxamidine is a noradrenergic neuron blocker and that its action is dependent on continued neuronal uptake. Following 6-hydroxydopamine incubation, 10^?5 M pyroxamidine and 10^?5 M guanethidine inhibited the responses to (?)-noradrenaline in the rat anococcygeus muscle. Thus it seems likely, at high concentrations, that these compounds have postsynaptic blocking activity.     

Mechanism of inhibition of catecholamine release from adrenal medulla by diphenylhydantoin and by low concentration of ouabain (10−10 M)

Summary Catecholamine (CA) release was studied in rat adrenal incubated in vitro. Inhibition of (Na +K)-ATPase either by omission of K⁺ from the incubation medium or by addition of a high concentration of ouabain (10^–3 M) caused increased release of CA from the adrenal. Diphenylhydantoin (DPH) (10^–5 M) inhibited the spontaneous as well as the acetylcholine (10^–4 M)-induced release of CA. However, in K⁺-free medium or in the presence of 10^–3 M ouabain, DPH had no significant effect on CA release. A low concentration of ouabain (10^–10 M) caused a significant inhibition of spontaneous and of acetylcholine-induced release of CA. In a K⁺-free medium ouabain (10^–10 M) had no effect on CA release. DPH (10^–5 M) and a low concentration of ouabain (10^–10 M) caused a significant activation of (Na+K)-ATPase in a membrane fraction of the adrenal medulla. It is suggested that DPH and low ouabain concentrations inhibit CA release from the adrenal by activation of the sodium pump. The possible mechanism involved is discussed.     

Dual Effect of the Muscarinic Agonist McN-A-343 on Vascular Neuroeffector Transmission

Abstract: The site and mechanism of action of McN-A-343 (4-m-chlorophenylcarbamoyloxy)-2-butynyltrime-thylammonium chloride) on sympathetic neuroeffector transmission in the rabbit isolated pulmonary artery was studied. Low concentrations (10^?6 — 3 × 10^?5 M) of McN-A-343 and cocaine enhanced (up to 210 and 236%, respectively) the contractions evoked by electrical-field stimulation, while higher concentrations (10^?4 — 3 × 10^?4 M) inhibited them. McN-A-343 (10^?4 M) caused an initial transitory potentiation (222% of control) of the stimulation-evoked contractions followed by an inhibition. In the presence of cocaine (3 × 10^?5 M), the potentiation caused by McN-A-343 was prolonged and the secondary inhibitory phase was thus abolished. Physostigmine (10^?5 — 10^?4 M), hexamethonium (10^?5 M), atropine (3 × 10^?7 M), suprofen (10^?5 M), and 4-aminopyridine did not alter the effect of McN-A-343 (10^?4 M). Cocaine (3 × 10^?5 M)and(+)-amphetamine (10^?5 M) reversed the McN-A-343-evoked block, while they did not alter the inhibition caused by tetracaine (3.2 × 10^?5 M). Atropine (3 × 10^?7 M) had no effect on the McN-A-343-induced block, while 4-aminopyridine (10^?4 M) caused a partial and transitory reversal. On the aorta McN-A-343 (10^?4 M) did not alter the contractile concentration-response curve of (—)-noradrenaline (10^?9 — 3 × 10^?4 M), while that of serotonin (10^?8 — 3 × 10^?5 M) was moved to the right in a competitive manner. McN-A-343 (10^?4 M) did not alter the contractions evoked by noradrenaline (10^?7 M) during the period corresponding to the stimulation-evoked enhancement and subsequent inhibition. McN-A-343 (10^?4 M) slightly antagonized the contractions caused by tyramine (10^?6 — 10^?3 M) and carbachol (10^?6 — 10^?3 M). It is concluded that McN-A-343 enhances stimulation-evoked transmitter release by a presynaptic facilitatory action mediated via receptors localized on the outer surface of adrenergic neurones and to a lesser extent by inhibition of noradrenaline re-uptake. The enhancement does not involve presynaptic nicotine or muscarine receptors. Furthermore, McN-A-343 inhibits transmitter release by acting as an adrenergic neurone blocking agent at an intraneuronal site. The inhibition does not involve presynaptic muscarine inhibitory receptors and is prostaglandin-independent.     

左旋四氢巴马汀与左旋千金藤啶碱的单胺受体结合特性与单胺排空作用的关系

本文报道了四氢异喹啉生物碱(TIQ):左旋千金藤啶碱(1—SPD),左旋及消旋四氢巴马汀(THP)及小檗胺(BBM)对大鼠脑内DA_2,5-HT_2及β—肾上腺素受体的结合特性。 所测的四种TIQ对β-肾上腺素受体的亲和力均很低(IC_(50)大于10~(-4)M)。结果表明,THP对单胺能神经递质受体亲和力远小于经典的单胺受体阻断剂,从而提示单胺受体阻断可能并非THP影响单胺能神经传递的主要机制。作者认为THP一类的TIQ,生物碱至少可以通过两种机制发挥作用:单胺受体阻断及利血平样“颗粒效应”。而对于THP,起主要作用的是引起单胺排空的“颗粒效应”。此外,实验中发现1-SPD与DA_2受体结合并不是简单的双分子反应,表现为1-SPD/[~3H]螺环哌啶酮抑制曲线的Hill系数远小于1。这一受体结合特点可能与其在动物行为实验中表现出的部分激动剂性质有关。     

Water‐insoluble fraction of airborne particulate matter (PM10) induces oxidative stress in human lung epithelial A549 cells

Exposure to ambient airborne particulate matter (PM) with an aerodynamic diameter less than 10 μm (PM₁₀) links with public health hazards and increases risk for lung cancer and other diseases. Recent studies have suggested that oxidative stress is a key mechanism underlying the toxic effects of exposure to PM₁₀. Several components of water‐soluble fraction of PM₁₀ (sPM₁₀) have been known to be capable of inducing oxidative stress in in vitro studies. In this study, we investigated if water‐insoluble fraction of PM₁₀ (iPM₁₀) could be also capable of inducing oxidative stress and oxidative damage. Human lung epithelial A549 cells were exposed to 10 μg/mL of sPM₁₀, iPM₁₀ or total PM₁₀ (tPM₁₀) preparation for 24 h. Here, we observed that all three PM₁₀ preparations reduced cell viability and induced apoptotic cell death in A549 cells. We further found that, similar to the exposure to sPM₁₀ and tPM₁₀, the intracellular level of hydrogen peroxide (H₂O₂) in the iPM₁₀‐exposed cells was increased significantly; meanwhile the activity of catalase was decreased significantly as compared with the unexposed control cells, resulting in significant DNA damage. Our data obtained from inductively coupled plasma‐mass spectrometry (ICP‐MS) assays showed that iron is the most abundant metal in all three PM₁₀ preparations. Thus, we have demonstrated that, similar to sPM₁₀, iPM₁₀ is also capable of inducing oxidative stress by probably inducing generation of H₂O₂ and impairing enzymatic antioxidant defense, resulting in oxidative DNA damage and even apoptotic cell death through the iron‐catalyzed Fenton reaction. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 226–233, 2014.     

Dual Inhibitory Action of ATP on Adrenergic Neuroeffector Transmission in Rabbit Pulmonary Artery

The aim of this study was to determine whether the inhibitory action of ATP on sympathetic neuroeffector transmission in the isolated pulmonary artery is due to ATP itself or one of its dephosphorylated breakdown products, ADP, AMP or adenosine. Furthermore, the mechanism of the inhibitory action was investigated. ATP (10^?6?3 × 10^?4 M), the degradation-resistant ATP-analogue, β, γ-methylene-5′-triphosphate (10^?5?3 × 10^?4 M), ADP (10^?6?3 × 10^?4 M), AMP (10^?5?3 × 10^?4 M), adenosine (10^?5?3 × 10^?4 M) and 2-chloroadenosine (10^?7?3 × 10^?4 M) reduced the contractions evoked by field-stimulation. This was also the case for prostaglandin E₂ (3 × 10^?9?3 × 10^?7 M), while prostaglandin F_2α(1.4 × 10^?8 M) slightly augmented the neurogenic response. The time course of the inhibitory effect of purinergic compounds on the stimulation evoked contractions was studied. In the case of ATP and ADP the inhibition was biphasic: an initial marked block (1 min. after drug addition) which in the continued presence of either compound recovered partially 10 min. later and then remained almost constant for another 90 min. The other purinergic agents caused a monophasic reduction. In the presence of indomethacin (5 × 10^?5 M), ATP and ADP also reduced the neurogenic contractions in a monophasic manner. Indomethacin did not alter the β,γ-methylene-5′-triphosphate-induced inhibition. Dilazep (3 × 10^?6 M) plus deoxycoformycin (3.6 × 10^?6 M), augmented the inhibitory effect of ATP. In contrast, theophylline (5 × 10^?5 M) did not alter the effect of ATP. The inhibitory effect of ATP (10^?4 M) on stimulation-evoked contractions was inversely proportional to the extracellular Ca²⁺ concentration (0.3–5.2 mM) and to frequency of stimulation (3–15 Hz). These results suggest that ATP initially causes a presynaptic inhibition of noradrenaline release evoked by field-stimulation. This phase I block is probably mainly due to an ADP-mediated short-lasting release of prostaglandins of the E type. The continuous inhibition (phase II) is probably due to ATP and its metabolites, possibly mainly adenosine. The phase II inhibition may possibly involve a decreased entry of Ca²⁺ into adrenergic nerve terminals during depolarization.     

Biphasic effects of the beta-adrenoceptor agonist, BRL 37344, on glucose utilization in rat isolated skeletal muscle.

1. The effects of the selective beta 3-adrenoceptor agonist, BRL 37344 (BRL) on glucose uptake and phosphorylation (i.e. glucose utilization; GU) and glycogen synthesis in rat isolated soleus and extensor digitorium longus (EDL) muscle preparations in vitro were investigated by use of 2-deoxy-[3H]-glucose (GU) and [U-14C]-glucose (glycogen synthesis). 2. Low concentrations of BRL (10(-11)-10(-9) M) significantly increased GU, with maximal increases of 30% in soleus and 24% in EDL at 10(-11) M. Neither the selective beta 1-adrenoceptor antagonist, atenolol (10(-8)-10(-6) M), nor the selective beta 2-adrenoceptor antagonist, ICI 118551 (10(-8)-10(-6) M) had any effect on the stimulation of GU induced by 10(-11) M BRL. 3. High concentrations of BRL (10(-6)-10(-5) M) caused significant inhibition (up to 30%) of GU in both soleus and EDL muscles. The inhibition of 10(-6) M BRL was blocked completely by 10(-6) and 10(-7) M ICI 118551 in soleus, and by 10(-6)-10(-8) M ICI 118551 in EDL; atenolol (10(-8)-10(6) M) had no effect. 4. Another selective beta 3-adrenoceptor agonist, CL 316,243, also caused a significant stimulation of muscle GU, with maximal increases of 43% at 10(-9) M in soleus and 45% at 10(-10) M in EDL. The stimulation of GU declined with further increases in the concentration of CL 316,243, but no inhibition of GU was seen, even at the highest concentration (10(-5) M) tested. 5. BRL at 10(-5) M inhibited completely insulin-stimulated glycogen synthesis in both soleus and EDL, but this inhibitory effect of BRL was abolished by 10(-6) M ICI 118551. BRL at 10(-11) M (with or without 10(-6) M ICI 118551) had no effect on insulin-stimulated glycogen synthesis. 6. It is concluded that: (i) low (< nM) concentrations of BRL stimulate GU via an atypical beta-adrenoceptor that is resistant to conventional beta 1-adrenoceptor and beta 2-adrenoceptor antagonists; (ii) the stimulation of GU is negated by the activation of beta 2-adrenoceptors that occurs at higher (> nM) concentrations of BRL; (iii) inhibition of GU via beta 2-adrenoceptor activation is associated with inhibition of glycogen synthesis, possibly due to activation of glycogenolysis; (iv) the opposing effects of beta 2-adrenoceptor and atypical beta-adrenoceptor activation on GU suggest that in skeletal muscle these adrenoceptors are linked to different post-receptor pathways.     

Prejunctional Muscarinic Receptor Modulation of Noradrenaline Release from Sympathetic Neurones in Rabbit Aorta *

The prejunctional muscarinic modulation of stimulation‐evoked release of ³H‐noradrenaline from sympathetic neurones in rabbit aorta was examined. The role of transmitter uptake, α‐adrenoceptor blockade, stimulation frequency and endothelium on the modulation was investigated. Rings of aorta were incubated with (‐)‐³H‐noradrenaline and subsequently subjected to electrical‐field stimulation. Fractional ³H‐overflow was determined by liquid scintillation counting. Acetylcholine (10^?8–3×10^?6 M) added cumulatively, reduced the stimulation‐evoked ³H‐overflow up to 80%. The effect of acetylcholine was the same in intact and endothelium‐free aorta. The inhibitory effect of acetylcholine was inversely related to the frequency of stimulation (1–10 Hz). The maximal inhibition (%) was 80 (1 Hz), 53 (3 Hz) and 14 (10 Hz). The inhibitory effect of acetylcholine (10^?6 M) and carbachol (10^?5 M) reached a maximum 15 min. after addition and then remained almost constant. Cocaine (3×10^?5 M) did not alter the effect of acetylcholine. Desipramine (10^?6 M) and corticosterone (4×10^?5 M) attenuated the inhibition seen with low concentrations (10^?8–10^?7 M) of acetylcholine. The acetylcholine‐induced inhibition was antagonized by desipramine. Cocaine plus corticosterone attenuated the inhibition seen with high concentrations (10^?6–3×10^?6 M) of acetylcholine. Rauwolscine (10^?6 M) enhanced the maximal inhibitory effect of acetylcholine. We conclude that the inhibitory effect of acetylcholine on ³H‐overflow from rabbit aorta preloaded with ³H‐noradrenaline is (1) inversely related to stimulation frequency; (2) independent of endothelium; (3) unaffected by neuronal and extraneuronal transmitter uptake; (4) that cocaine is not a prejunctional muscarinic antagonist; (5) that cocaine, but not desipramine, is suited as a neuronal uptake inhibitor in studies of prejunctional muscarinic receptor subtypes; and (6) and that there is an inverse interaction between prejunctional α₂‐adrenoceptors and muscarinic receptors.     

Contribution of Rho-kinase in human gallbladder contractions

Rho/Rho-kinase-mediated pathway has been involved in a variety of physiological processes, including Ca²⁺ sensitization, which enhances smooth muscle contraction. In this study, first of all we investigated the expression of Rho-kinase (ROCK-2) and then the role of this protein in the control of smooth muscle contraction in the isolated human gallbladder. For this purpose, we examined the effects of a selective Rho-kinase inhibitor, (+)- (R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632, 10^− 8 − 3 × 10^− 5 M) on carbachol (10^− 8–10^− 4 M), cholecystokinin-8 (10^− 8 M), endothelin-1 (10^− 8 M), histamine (10^− 5 M), neurokinin A (10^− 7–10^− 6 M), 5-hydroxytryptamine (10^− 6–10^− 5 M) and potassium chloride (KCl, 25–50 mM)-induced contractions as well as spontaneous contractile activity. Y-27632 (10^− 5 M) significantly reduced 5-hydroxytryptamine, neurokinin A and KCl-induced contractions. Moreover, this Rho-kinase inhibitor (10^− 8 − 3 × 10^− 5 M, cumulatively) relaxed the contractions produced by cholecystokinin-8, endothelin-1 and histamine in a concentration-dependent manner, being the pEC₅₀ values for Y-27632 5.74 ± 0.12, 5.33 ± 0.09 and 5.95 ± 0.18, respectively. Carbachol (10^− 8–10^− 4 M) pfroduced concentration-dependent contractions, which were also inhibited significantly by Y-27632. In addition, the spontaneous contractile activity was suppressed in the presence of Y-27632 (10^− 6–10^− 5 M). Moreover, Western blot analysis has revealed that Rho-kinase is expressed in homogenates of the human gallbladder. Taken together, these results show that Rho-kinase is expressed in the human gallbladder, and it has an essential role in agonists and depolarization-induced contractions as well as spontaneous contractile activity.     

Effect of Dopexamine Hydrochloride on Contractions of Rabbit Isolated Aorta Evoked by Various Agonists

The inhibitory affinity of dopexamine hydrochloride to postsynaptic adrenoceptors, cholinoceptors, 5-hydroxytryptamine and histamine receptors was studied in rabbit isolated aorta. Dopexamine (10^?7–10^?5M) antagonized competitively the contractions of rabbit aorta evoked by noradrenaline (pA₂: 6.60). Neither cocaine plus corticosterone nor cocaine, corticosterone plus propranolol altered the inhibition (pA₂: 6.77 and 6.63, respectively). The antagonism of dopexamine against noradrenaline-evoked contractions was the same after 1 and 4 hr of pretreatment with dopexamine. In the presence of cocaine plus corticosterone, dopexamine antagonized the contractions evoked by phenylephrine (pA₂: 6.94). Removal of endothelium did not influence this antagonism (pA₂: 7.06). Dopexamine (10^?7–10^?5M) did not antagonize the contractions of aorta evoked by histamine (3×10^?7–6 × 10^?5M) and by 5-hydroxytryptamine (3 × 10^?7 –3 × 10^?4M). Dopexamine (10^?8 and 10^?7M) did not alter the contractions of endothelium-free aorta evoked by carbachol. Dopexamine (10^?7–10^?5M) slightly enhanced the contractions of aorta evoked by potassium (10^?2–5.5 × 10^?2M). These results suggest that dopexamine is an α₁-adrenoceptor antagonist. Furthermore, dopexamine has no affinity to cholinoceptors, histamine and 5-hydroxytryptamine (5-HT₂) receptors and is apparently not a calcium antagonist.     

Frequency-Dependence of 3H-Noradrenaline Release from Rabbit Pulmonary Artery: Effect of α-Adrenoceptor Antagonists and Inhibitors of Transmitter Inactivation

Abstract: The aim of this study was to examine the modulating role of presynaptic α₂-adrenoceptors on transmitter release from vascular sympathetic neurones. This was done by examining the influence of removal of inactivation pathways on the effect of α-adrenoceptor antagonists on the release of transmitter from noradrenergic neurones. The rabbit main pulmonary artery preloaded with ³H-noradrenaline (³H-NA) was used. The artery was stimulated with 300 pulses at various frequencies (1, 3, 10 and 30 Hz). Pargyline (3 × 10^?4M) increased the stimulation-evoked ³H-overflow at 1 and 3 Hz and decreased it at 30 Hz. U-0521 (3′,4′-dihydroxy-2-methylpropiophenone; 3 × 10^?6M) enhanced the overflow at 1 Hz and had no effect at 3–30 Hz. Corticosterone (4 × 10^?5M) did not alter the stimulation-evoked ³H-overflow at 1–30 Hz. Cocaine (3 × 10^?6M) enhanced the ³H-overflow slightly at 1–30 Hz. At 3 × 10^?5M, cocaine enhanced ³H-overflow at 1 Hz and reduced it at 30 Hz. Neither corticosterone (4 × 10^?5M) nor propranolol (10^?7M) modified this effect of cocaine. Propranolol (10^?7M) alone decreased the ³H-overflow at 30 Hz and had no effect at 1–10 Hz. Phenoxybenzamine (10^?6M) and chlorpromazine (3 × 10^?6M) potentiated the stimulation-evoked ³H-overflow at 1–30 Hz. Phentolamine (10^?6M) decreased the ³H-overflow at 1 Hz and enhanced it at 3–30 Hz. Rauwolscine (10^?6M) enhanced the stimulation-evoked ³H-overflow maximally at 10 Hz and had no effect at 1 and 30 Hz. Cocaine (3 × 10^?5M), cocaine (3 × 10^?5M) + corticosterone (4 × 10^?5M), pargyline (3 × 10^?4M) and U-0521 (3 × 10^?6M), but not corticosterone (4 × 10^?5M), increased the rauwolscine-induced enhancement at 1 and 3 Hz, but had no influence at 10 and 30 Hz. It is concluded that at a low frequency (1 Hz) of nerve stimulation, inhibition of either neuronal uptake, extraneuronal uptake, monoamine oxidase (MAO) or catechol-O-methyltransferase (COMT) causes an enhancement in transmitter overflow that is due to removal of inactivation pathways. The enhancement is not mediated via facilitatory β-adrenoceptors. At higher frequencies (3–30 Hz) inhibition of either neuronal uptake or MAO causes a sufficient amount of transmitter in the neuromuscular gap to activate the presynaptic α-adrenoceptor mediated negative feed-back system causing a decrease in transmitter release. α- Adrenoceptor antagonists enhance the stimulation-evoked release of ³H-NA only when the junctional gap concentration of transmitter is sufficient to trigger the presynaptic α-adrenoceptor auto-inhibitory system.     

An efficient procedure for the regioselective synthesis of 10-methoxy-11-hydroxyaporphine from (R,S)-10,11-dihydroxyaporphine

A regioselective preparation of 10-methoxy-11-hydroxyaporphine (“Apocodeine,1b”) from (R,S)-10, 11-dihydroxyaporphine(apomorphine,1a) is described. The isopropylidene ketal ring of 10,11-(isopropylidenyldioxy) aporphine (2) obtained by the isopropylidenation of apomorphine, was regioselectively opened by the ten equivalent of trimethylaluminum to give 10-hydroxy-11-t-butyloxyaporphine (3). The free 10-hydroxyl position of 3 was methylated with methyl p-toluenesulfonate/NaH, and afforded 10-methoxy-11-t-butyloxyaporphine (4) in high yield. Selective debutylation gave the desired 10-methoxy-11-hydroxyaporphine (“apocodeine”,1b) in good yield.