Effect of desmethyldiazepam and chlordesmethyldiazepam on 3′,5′-cyclic guanosine monophosphate levels in rat cerebellum

Three different benzodiazepines (diazepam, its pharmacologically active metabolite desmethyldiazepam, and the derivative chlordesmethyldiazepam) have been compared in our study for their effects on 3,5-guanosine monophosphate (cGMP) cerebellar levels. Desmethyldiazepam and chlordesmethyldiazepam are several-fold more potent that diazepam in decreasing rat cyclic cGMP cerebellar concentrations. None of the three drugs induces detectable changes of cerebellar cyclic 3,5-adenosine monophosphate (cAMP).On the other hand, the three compounds did not modify the levels of cGMP in cerebellum of newborn rats, where Purjinje cell and dendrites lack synaptic contacts. However, injection of gamma aminobutyric acid (GABA) in the newborn is still able, as in the adult, to decrease cGMP concentration in cerebellum. Our data support the hypothesis that cGMP cerebellar concentrations may be a reliable biochemical marker of the clinical activity of benzodiazepines.     

Alterations of dopaminergic neurotransmission after chronic morphine treatment: Pre- and postjunctional studies in striatal tissue

Summary Repeated morphine administration reversed the acute effects of morphine in rats, e.g. catalepsy and akinesia, and induced symptoms suggesting an activation of dopaminergic mechanisms. In morphinewithdrawn rats, the potency or intrinsic activity of dopamine in stimulating the synthesis of cyclic AMP in striatal homogenates was not significantly altered. However, the K⁺-induced release of¹⁴C-dopamine from striatal slices of morphine-withdrawn rats was significantly increased, compared with that from striatal slices of saline-treated controls. The results suggest that chronic morphine administration to rats increases the dopaminergic neurotransmission in brain by a pre-synaptic (prejunctional) mechanism, probably reflecting some kind of adaptation to the acute morphine action, which decreases the dopaminergic neurotransmission. The nigro-striatal dopaminergic system, therefore, seems to be a good model to study acute morphine actions and mechanisms of morphine dependence at the cellular level.Some of these results were presented at the Symposium on Acute Effects of Narcotic Analgesics in Nokkala, Espoo, Finland, July 18–20, 1975, and at the Vth Congress of the Polish Pharmacological Society, Szczecin, Sept. 24–27, 1975     

Effects of nitric oxide donors on the afferent resting activity in the cephalopod statocyst

The effects of bath applications of the nitric oxide (NO) donors sodium nitroprusside (SNP), diethylamine sodium (DEA), 3-morpholinosydnonimine (SIN-1), and S-nitroso-N-acetyl-penicillamine (SNAP) on the resting activity (RA) of afferent crista fibers were studied in isolated statocysts of the cuttlefish Sepia officinalis. The NO donors had three different effects: inhibition, excitation, and excitation followed by an inhibition. The SNAP analog N-acetyl-DL-penicillamine (xSNAP; with no NO moiety) had no effect. When the preparation was pre-treated with the NO synthase inhibitor N(G)-nitric-L-arginine methyl ester HCl (L-NAME), the NO donors were still effective. When the preparation was pre-treated with the guanylate cyclase inhibitors methylene blue (M-BLU) or cystamine (CYS), NO donors had only excitatory effects, whereas their effects were inhibitory only when pre-treatment was with the adenylate cyclase inhibitors nicotinic acid (NIC-A), 2',3'-dideoxyadenosine (DDA), or MDL-12330A. When pre-treatment was with a guanylate and an adenylate cyclase inhibitor combined, NO donors had no effect; in that situation, the RA of the afferent fibers remained and the preparation still responded to bath applications of GABA. Selective experiments with statocysts from the squid Sepioteuthis lessoniana and the octopod Octopus vulgaris gave comparable results. These data indicate that in cephalopod statocysts an inhibitory NO-cGMP and an excitatory NO-cAMP signal transduction pathway exist, that these two pathways are the key pathways for the action of NO, and that they have only modulatory effects on, and are not essential for the generation of, the RA.     

Tyrosine kinase effects on adrenoceptor-stimulated cyclic AMP accumulation in preoptic area and hypothalamus of female rats: modulation by estradiol

These studies examined the functional interactions between adrenergic G-protein coupled receptors and protein tyrosine kinases in the preoptic area and hypothalamus, brain regions that regulate reproductive function in female rats, and evaluated whether in vivo treatment with estradiol for 2 days modulates the cross-talk between these two signaling pathways. In hypothalamic slices genistein, a general tyrosine kinase inhibitor, enhances norepinephrine-stimulated cAMP synthesis independent of estradiol treatment. Genistein appears to act by increasing beta-adrenoceptor signaling. At high norepinephrine concentrations, estradiol potentiates genistein enhancement of the cAMP response in hypothalamic slices. This interaction between estradiol and genistein appears to involve modification of alpha(2)-adrenoceptor signaling mechanisms. In preoptic area slices, genistein enhancement of norepinephrine-stimulated cAMP synthesis is only observed in estradiol-treated rats. In this brain region, genistein enhances cAMP accumulation by modifying alpha(1)- and/or alpha(2)-adrenoceptor rather than beta-adrenoceptor signaling. Genistein amplification of norepinephrine-stimulated cAMP synthesis is not mediated by interactions with estrogen receptors, or by regulation of adenylyl cyclase or phosphodiesterase activities. At the concentration used, genistein inhibits tyrosine phosphorylation in slices from both brain regions. Daidzein, an inactive analogue of genistein, fails to enhance the norepinephrine-stimulated cAMP response in either brain region independent of hormone treatment. These results suggest that protein tyrosine kinases regulate adrenergic responses in the hypothalamus and preoptic area. Moreover, the functional interaction between adrenergic G-protein coupled receptor signaling and protein tyrosine kinases is modified in a brain region and receptor subtype specific manner by estradiol.     

Soluble guanylate cyclase

Soluble guanylate cyclase (sGC) is a heterodimeric haemoprotein, which represents the intracellular receptor for the ubiquitous biological messenger nitric oxide (NO). Activation of the enzyme facilitates conversion of GTP to the intracellular second messenger cGMP, and it is this molecule which mediates the majority of biological actions attributed to NO. sGC is expressed in virtually all mammalian cells and is important in mediating numerous physiological processes, including vascular and non-vascular smooth muscle relaxation, peripheral and central neurotransmission, platelet reactivity and phototransduction. Due to its ubiquitous nature, the pathogenesis of various disease states has been linked to aberrations in sGC signalling. This is especially true of the cardiovascular system, where inappropriate activation of sGC may underlie conditions such as stroke, atherosclerosis, impotence and septic shock; however, altered sGC activation has also been associated with the pathogenesis of asthma and certain neurodegenerative disorders. Therefore, agents that can modulate sGC function selectively will have considerable therapeutic potential, particularly in the treatment of cardiovascular disease.     

Stimulation of aldosterone production in vitro and its inhibition by spironolactone

Summary The synthesis of aldosterone was stimulated in vitro by ACTH, dibutyryl-cyclic AMP, potassium ions and angiotensin II. Aldosterone was determined by a method involving two thin layer chromatographies (TLC), a periodic acid oxidation step, and a final esterification with heptafluorobutyric anhydride to prepare the aldosterone--lactone-heptafluorobutyrate for gas chromatographic quantification with electron-capture detection. The method is described in detail.Spironolactone (6×10^–5–1×10^–4M) added to the incubation medium inhibited the synthesis of aldosterone in a dose-dependent manner, while the production of corticosterone was not affected.It is concluded that spironolactone inhibits the conversion of corticosterone to aldosterone.     

中美药品GMP比较研究

比较中美两国GMP立法的差异,即中美两国GMP在法律和文化上的不同。中国制药企业要达到美国FDAcGMP符合性,应加强建立程序和证据。     

Combined paracetamol and amitriptyline adsorption to activated charcoal

Objectives. High-gram drug doses seen in multiple-drug poisonings might be close to the adsorption capacity of activated charcoal (AC). The aim was to determine the maximum adsorption capacities (Q_m) of amitriptyline and paracetamol, separately and in combination, to AC. Methods. ACs (Carbomix® and Norit Ready-To-Use) were tested in vitro. At pH 1.2 and pH 7.2, 0.250 g AC and paracetamol and/or amitriptyline were mixed and incubated. The AC?:?drug ratios were 10?:?1, 5?:?1, 3?:?1, 2?:?1, and 1?:?1. The mixed-drug adsorption vials contained the same AC?:?paracetamol ratios, but amitriptyline was added as fixed dose (0.080 g) to all samples. Drug concentrations in the liquid phase were analyzed using high-performance liquid chromatography (HPLC)/UV-detection. Results. Q_m, amitriptyline, were 0.49 g/g Carbomix® and 0.70 g/g Norit Ready-To-Use, and Q_m, paracetamol, were 0.63 g/g Carbomix® and 0.72 g/g Norit Ready-To-Use. The tested pH differences had minor effect on the adsorption. The mixed-drug adsorption showed about 40% Q_m reduction of each drug with increasing amounts of drug/g AC, but the total gram of drug adsorbed to AC was increased compared to one-drug conditions. Conclusion. The adsorption of the two compounds to AC seems to compete resulting in lower maximum adsorption capacity for both drugs when mixed. However, a great adsorptive capacity was noted and might be explained by adsorption of the drugs to different AC surface sites. Furthermore, the Norit Ready-To-Use preparation, with less volume and total weight for the same AC dose as Carbomix®, showed a higher Q_m. This might be clinically significant in terms of preventing nausea, vomiting, and subsequent aspiration.     

Human VIP-α: an emerging biologic response modifier to treat primary pulmonary hypertension

Primary pulmonary hypertension (PPH) is a rare life-threatening disorder of unknown etiology manifested by chronic elevation of pulmonary arterial pressure. Given that pulmonary vasoconstriction, endothelial and vascular smooth muscle cell proliferation and in situ thrombosis contribute appreciably to the evolution of PPH, treatment with vasodilators, antiproliferative drugs and anticoagulants, alone or in combination, constitute the pharmacologic standard of care. To this end, long-term administration of oral calcium channel blockers, prostacyclin analogs by various routes and oral endothelin-1 receptor antagonists, alone or in combination, is efficacious in treating patients with PPH. Unfortunately, efficacy is hampered by poor stability, delivery and bioavailability, and by systemic toxicity. Hence, there is an ongoing need to develop and test new drugs to treat patients with PPH. To address this issue, a novel, targeted, long-acting, biocompatible and safe sterically stabilized liposomal and micellar formulation of human vasoactive intestinal peptide (VIP) was developed and tested for human use: the 28-amino acid pleiotropic biologic response modifier, human VIP-α. The long-lasting salutary effects of phospholipid-associated VIP on vasomotor tone and arterial pressure were expressed at low concentrations solely in diseased animals and were independent of its route of administration. Thus, the author proposes that human VIP-α could be developed as a safe long-acting drug to treat patients with PPH.