Kenichi Kishii

Novel diphenylalkyl piperazine derivatives with high affinities for the dopamine transporter

The novel diphenyl piperazine derivatives containing the phenyl substituted aminopropanol moiety, including 1-[4,4-bis(4-fluorophenyl)butyl]-4-[2-hydroxy-3-(phenylamino)propyl]piperazine 1, which were modified at the connective between the diphenyl and piperazine moieties, have been found to be potent dopamine uptake inhibitors. To study the further structure-activity relationship (SAR) of these compounds, a new series was synthesized, with modifications at the 2-hydroxy-3-phenylaminopropyl moiety of 1. The series was evaluated for dopamine transporter (DAT) binding affinity with [3H]GBR12935 in rat striatal membranes. Most of the compounds showed moderate to high DAT binding affinities and some were approximately equivalent in activity to compound 1 or GBR12909 as a dopamine uptake inhibitor, with IC(50) values of nanomolar range. The SAR suggested that on exhibiting a potent interaction with the DAT, there is probably a steric limitation around the benzene ring of the phenylamino moiety of 1, allowing only small-sized substituents with the exception of basic moieties at the 4-position. In addition, the SAR at the 3-amino-2-propanol moiety of 1 suggested that either the nitrogen atom with an electron donating substituent or the unsubstituted nitrogen atom and also the hydroxy group are desirable for elicitation of a potent DAT binding affinity.

Effects of LP-805, a novel vasorelaxant agent, a potassium channel opener, on rat thoracic aorta

1. In rat thoracic aorta, LP-805 (0.1-10 microM) caused the marked reduction of NE-induced maximum response and relaxed the low K+ (less than 35.9 mM)-induced contraction, in a concentration-dependent manner, but failed to relax the high K+ (65.9 mM)-induced contraction. 2. Glibenclamide (0.3-1 microM) caused a parallel shift of concentration-response curve produced by LP-805 for 25.9 mM K(+)-induced contraction and prevented the LP-805-induced reduction in maximum response evoked by NE in a concentration-dependent manner. 3. Glibenclamide (10 microM) prevented the LP-805 (10 microM)-induced decrease in cytosolic Ca2+ levels which was increased by 1 microM NE or 25.9 mM K+. 4. LP-805 (10 microM) increased basal 86Rb efflux, which was completely inhibited by 10 microM glibenclamide. 5. The results suggest that LP-805 causes a vasorelaxation as a consequence of the decrease in cytosolic Ca2+ levels due to the increase in K+ efflux via opening ATP-dependent K+ channels.

Novel diphenylalkyl piperazine derivatives with dual calcium antagonistic and antioxidative activities

Two types of novel diphenylalkyl piperazine derivatives containing the thio or aminopropanol moiety substituted by phenyl or benzyl group were synthesized, and evaluated for their calcium antagonistic and antioxidative activities. These compounds showed apparent inhibitions against KCl-induced contractions in isolated rat aorta. Among them, phenylamino compound 9 and benzylamino compound 13 also possessed potent inhibitory activities against auto-oxidative lipid peroxidations in canine brain homogenates. Two representative compounds 3a and 9 were evaluated for their inhibitory activities against KCl-induced contractions in isolated canine arteries (basilar, coronary, mesenteric, and renal). Both compounds showed the most potent inhibitions to basilar artery.

Syntheses of novel diphenyl piperazine derivatives and their activities as inhibitors of dopamine uptake in the central nervous system

A new series of diphenyl piperazine derivatives containing the phenyl substituted aminopropanol moiety, which were modified at sites between the diphenyl and piperazine moieties, was prepared and evaluated for dopamine transporter binding affinity with [(3)H]GBR12935 in rat striatal membranes. These synthesized compounds showed apparent dopamine transporter binding affinities (IC(50)<30 nM) and some of them were approximately equivalent in activity to GBR12909 known as a potent dopamine uptake inhibitor, showing the activities with IC(50) values of nanomolar range. Among them, 1-[4,4-bis(4-fluorophenyl)butyl]-4-[2-hydroxy-3-(phenylamino)propyl]piperazine 2 was evaluated for extracellular dopamine levels in rat striatum using in vivo brain microdialysis. The intraperitoneal administration of 2 (0.01, 0.03, or 0.1 mmol/kg) induced dose-dependent increases of dopamine levels in rat striatal dialysates. The maximum increases in dopamine levels induced by 2 were greater than those by GBR12909. The pharmacological data of these novel diphenyl piperazine derivatives show that the compounds have potent dopamine uptake inhibitory activities in the central nervous system.

Effects of LP-805, a new vasodilating agent, on cytosolic Ca2+ and contraction in vascular smooth muscle of rat aorta

1. LP-805 (0.1-10 microM) caused the reduction in norepinephrine (NE)-and serotonin (5-HT)-induced maximum response, a parallel shift of the concentration-response curve for prostaglandin F2 alpha (PGF2 alpha), in a concentration-dependent manner, but not K(+)-induced maximum response. 2. In Ca(2+)-free solution, LP-805 (0.1-10 microM) markedly inhibited the phasic contraction induced by 0.3 microM NE and the contraction induced by Ca2+ (0.1-2 mM) in the presence of 0.3 microM NE, in a concentration-dependent manner. Similar results were obtained in the presence of 5-HT (10 microM) or PGF2 alpha (10 microM). 3. In fura-2 loaded strips, ryanodine (10 microM) and LP-805 (10 microM) abolished 1 microM NE- and 30 microM 5-HT-induced phasic contractions, and inhibited the increase in cytosolic Ca2+ levels by both the agonists in the absence of external Ca2+, but had no influence on the following sustained contractions. 4. The effects of LP-805 on PGF2 alpha-induced Ca2+ transient and large sustained contraction were similar to those of ryanodine. 5. These results suggest that a vasodilatory effect of LP-805 might account for inhibiting the mobilization of external Ca2+ through receptor mediated passway and the Ca2+ release from a ryanodine sensitive Ca2+ store.

Endothelium-dependent vasodilation by LP-805, a novel vasodilating agent, on rat thoracic aorta

1. In rat aortae with [E(+)-tissue] and without [E(-)-tissue] intact endothelium, LP-805 relaxed the preparations precontracted with 35.9 mM K+ and its action in E(+)-tissues was more potent than that in E(-)-tissues. Moreover, the inhibitory action of glibenclamide in E(-)-tissues was more potent than that in E(+)-tissues. 2. The relaxing action of LP-805 on E(+)-tissues treated with NG-nitro-L-arginine methyl ester (10 microM), a potent inhibitor of nitric oxide synthesis, was the same as that in E(-)-tissues. 3. Methylene blue (10 microM) also inhibited the LP-805 induced relaxation in E(+)-tissues. 4. Indomethacin (10 microM) had no effect on LP-805-induced relaxation in E(+)-tissues. 5. These results suggest that the vasorelaxant action of LP-805 involves the mechanism which causes the release of nitric oxide (NO) from vascular endothelium.

Ca-entry blockers, verapamil and diltiazem, on α1-adrenoceptors in thoracic aorta, renal artery and portal vein from rabbit

1. Verapamil caused a parallel shift of the concentration-response curve for norepinephrine in rabbit thoracic aorta and the reduction in norepinephrine-induced maximum response with shifts of the concentration-response curve for norepinephrine in renal artery and portal vein. 2. Diltiazem was without any effects on the response of thoracic aorta to norepinephrine, while the responses of renal artery and portal vein to norepinephrine were inhibited noncompetitively by diltiazem. 3. Verapamil but not diltiazem diminished markedly dibenamine-induced inhibition of maximum response to norepinephrine in all the preparations used. 4. Specific bindings of [3H]prazosin to both the membrane fractions derived from thoracic aorta and renal artery were displaced concentration-dependently by verapamil and diltiazem, but the effective concentrations of diltiazem were more than those for Ca-entry blocking activity. 5. These results suggest that verapamil might antagonize norepinephrine at alpha 1-adrenoceptors and the effective concentration for Ca-entry blocking activity of diltiazem were less than those for the interaction of diltiazem with alpha 1-adrenoceptors.

Effects of LP-805, a new vasodilating agent, on rat thoracic aorta

1. In canine coronary arteries, the contraction induced by prostaglandin F2 alpha (PGF2 alpha), but not by 65.9 mM K+, were relaxed by LP-805 (0.01-10 microM) in a concentration-dependent manner. 2. In rat thoracic aorta, LP-805 (0.1-10 microM) also relaxed the preparations contracted with norepinephrine (NE) and PGF2 alpha, but did not relax the contraction produced by 65.9 mM K+. 3. LP-805 (3-10 microM) inhibited the increase in cytosolic Ca2+ levels and contractions evoked by NE (1 microM) in the absence or presence of external Ca2+ in rat thoracic aorta. 4. LP-805 (0.1-10 microM) inhibited synthesis of IP3 induced by NE (0.3 microM) and cyclic AMP phosphodiesterase activity, and increased intracellular cyclic AMP levels in rat thoracic aorta. 5. These results suggest that a vasodilatory effect of LP-805 is due to inhibiting the increase in cytosolic Ca2+ levels via stimulation of various receptors, modulating second messenger synthesis.