(i) The anti-ischemic but not the anti-arrhythmic effect of cicletanine may involve opening of KATP. (ii) opening of KATP attenuates, inhibition of the channel exacerbates functional consequences of coronary occlusion, and (iii) KATP opening attenuates reperfusion-induced VF, but it triggers ischemia-induced VF. KATP blocking does not affect VF.

[3H]Rauwolscine binding to alpha 2-adrenoceptors in cerebral cortex and hippocampus membranes of young (4 months) and aged (24 months) Wistar rats has been investigated. In aged rats, Bmax values of [3H]rauwolscine binding were significantly reduced (25-32%) in the cerebral cortex and hippocampus, as compared with the number of alpha 2-adrenoceptors found in young rats. Chronic treatment with Ginkgo biloba extract did not alter [3H]rauwolscine binding in the hippocampus of young rats, but significantly increased (28%) the [3H]rauwolscine binding density in aged rats. These data confirm the previously described age-related noradrenergic alteration and suggest that noradrenergic activity in aged rats is more susceptible to Ginkgo biloba extract treatment.

We examined the effect of platelet-activating factor (PAF) on gastric acid secretion by isolated rabbit gastric glands as determined by [14C]aminopyrine ([14C]AP) uptake. PAF, histamine, and carbachol time- and concentration-dependently stimulated [14C]AP uptake, with estimated half-maximal effective concentrations of 60 pM, 0.25 microM, and 0.1 microM, respectively. PAF-induced [14C]AP uptake was inhibited by the specific PAF antagonists BN-50727 and SR-27417 and by the proton pump inhibitors omeprazole and lansoprazole. However, the H2-receptor antagonist famotidine had no effect. Buffering extracellular Ca2+ by ethylene glycol-bis(beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid resulted in a shift to the right of the time-course effect of PAF without altering the maximal response, whereas buffering intracellular Ca2+ by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid 2-acetoxymethyl ester, as well as blocking Ca2+ channels by verapamil, inhibited PAF-induced [14C]AP uptake. Intracellular Ca2+ concentration in isolated rabbit gastric glands, as measured by fura 2-acetoxymethyl ester, concentration-dependently increased in response to PAF, to a maximum of 1.5-fold for 0.1 microM. These results suggest that PAF stimulates gastric acid secretion via specific receptors activating intracellular Ca2+ mobilization, which could be located on the parietal cells.

Cicletanine hydrochloride is a new antihypertensive molecule synthetized and studied in our laboratory. Its chemical structure is uncommon for an antihypertensive molecule; it is characterized by the presence of a furopyridine group. Cicletanine is, therefore, a member of a new family of compounds with primarily antihypertensive properties, although some of the furopyridine derivatives have also antiallergic and antiinflammatory effects.The mechanism by which cicletanine lowers blood pressure has not been definitively established, although it appears to differ from that of other classes of antihypertensive drugs. Cicletanine acts on vascular smooth muscle by increasing prostacyclin synthesis and by interacting either directly with cytosolic Ca2+ pools or indirectly through various agents capable of mobilizing intracellular Ca ' ' , e.g., histamine.Studies in animals and humans demonstrated that the antihypertensive effect of cicletanine is clearly dissociable from its renal effect, which can be seen only at highdose levels of the drug.Clinical trials have confirmed the efficacy and safety of cicletanine in the treatment of hypertension, both as monotherapy or in combination with other antihypertensive drugs. CHEMISTRYCicletanine was synthetized by Esanu et al. (9) in the research laboratories of Institute Henri Beaufour, Le Plessis-Robinson (France). It was selected from a large number of furopyridines for its specific antihypertensive activity and very low, if any, toxicity. The chemical structure of cicletanine ( HCl) : (-+ ) 3-(4-chloropheny1)-1,3dihydro-7-hydroxy-6-methyl furo[3,Cc]pyridine is shown in Fig. 1. Its chemical synthesis from 2-,2,8-trimethyl-5-formyl pyrido [ 4,3-el 1,3-dioxine has been described (9). Cicletanine HC1 has a molecular weight of 298.2. It is not soluble in 166 CICLE TANINE 167 water, but soluble in ethanol and dimethyl sulfoxide. It is a white crystalline powder with a melting point of 2 19-228°C. PHARMACOLOGY Effect on Blood PressureThe activity of cicletanine on blood pressure was evaluated in anesthetized normotensive rats and dogs and in several models of hypertensive rats: desoxycorticosterone acetate, spontaneously ( SH ) and stroke-prone spontaneously ( SH-SP) hypertensive rats and rats with stress-induced hypertension.In the anesthetized normotensive rat, cicletanine, administered orally at 100 and 300 mg/kg, did not affect either mean blood pressure or heart rate. The blood pressure effects of epinephrine, norepinephrine, acetylcholine, isoproterenol, or serotonin were not altered by pretreatment with cicletanine.The effect of intravenously injected cicletanine on the main hemodynamic cardiovascular parameters-systolic and diastolic aortic pressure, heart rate, aortic blood flow, coronary (circumflex artery) and femoral arterial blood flow-were studied in anesthetized normotensive dog. At doses higher than 5 mg/kg i.v., cicletanine produced only a slight and transient bradycardia, a minor reduction of systolic arterial pressure, and a brief decrease in diastolic pressure. F...

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