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Effects of long-term sarpogrelate (5-HT2 antagonist) administration on the systolic blood pressure of Wistar-Kyoto normotensive rats (WKYs) and spontaneously hypertensive rats (SHRs) were studied and compared with those of quinapril (ACE-I). Sarpogrelate and quinapril were administered orally for 12 weeks and body and heart weights, systolic blood pressure and the relationships between heart weight and systolic blood pressure were determined. Although both drug treatments caused decreases in the body weight of WKYs and SHRs, only quinapril induced a decrease in the heart weight of SHRs. In addition, quinapril induced a dose-dependent decrease in systolic blood pressure in WKYs and SHRs while sarpogrelate had no effect on systolic blood pressure. Thus, quinapril showed hemodynamic effects on WKYs and SHRs, but the 5-HT2 antagonists sarpogrelate did not shown such effects, suggesting that 5-HT2 receptor antagonists may not be important for controlling systolic blood pressure.

In isolated porcine coronary arteries, concentrations of 5-HT (10–8 to 3 × 10–5 mol/l), α-methylserotonin (α-Me-5-HT, 10–8 to 3 × 10–5 mol/l) and ergonovine (10–9 to 3 × 10–4 mol/l) produced contraction, whereas high concentrations (10–5 to 10–4 mol/l) of these drugs produced relaxation. Both sarpogrelate and ketanserin produced rightward shifts of contraction concentration-response curves induced by 5-HT and α-Me-5-HT at the concentration from 10–9 to 3 × 10–5 mol/l, and only sarpogrelate inhibited the relaxation at high concentrations of 5-HT and displayed 155% of maximal contraction at 10–4 mol/l 5-HT. On the other hand, sarpogrelate and ketanserin did not show any inhibitory effects on the relaxation induced by high concentrations of ergonovine. These results suggested that sarpogrelate and ketanserin show different inhibitory effects on the relaxation induced by high concentrations of 5-HT, indicating that these two drugs may have different affinities to 5-HT receptor subtypes that may be involved in relaxation.

The dissociating and/or residual inhibitory effects of bopindolol from β-adrenoceptors (ARs) of atria strips pretreated with this drug and washed out with buffers on isoprenaline-induced chronotropic actions were determined. The effects of this drug were compared with those of its active metabolite 18-502, propranolol, and pindolol. Our results are as follows: (1) Lower concentrations of bopindolol (10–9 and 10–8 mol/l) and the active metabolite 18-502 (10–9 mol/l), propranolol (10–8 and 10–6 mol/l) and pindolol (10–8 mol/l) produced rightward shifts of concentration-response curves of isoprenaline. (2) Higher concentrations of bopindolol (10–7 mol/l) and 18-502 (10–8 and 10–7 mol/l) produced a reduced maximum response by isoprenaline. (3) Bopindolol (10–9–10–7 mol/l), 18-502 (10–9–10–7 mol/l) and propranolol (10–7 and 10–6 mol/l) did not recover to control levels at 180 min even after washout with buffers. In conclusion, bopindolol and 18-502 may slowly dissociate and act as noncompetitive β-antagonists rather than readily reversible β-AR antagonists. These effects may differ from those of propranolol and pindolol, although propranolol did not recover to control levels after washout with buffer.

This study was performed to assess the affinity of tamsulosin to the α1L- in addition to α1B-adrenoceptor (α1-AR) subtypes coexisting in the canine aorta using the radioligand binding assay. The antagonistic effects of this drug on contraction of the rat aorta were also assessed, and the results were compared with those obtained with prazosin, amosulalol, labetalol, ketanserin, clonidine and propranolol. The pKi value of tamsulosin to the α1L-subtype was lower than those of prazosin and HV-723, but higher than those of amosulalol, ketanserin and labetalol. The pKi value of tamsulosin for the α1B-subtype in the canine aorta was similar to that of prazosin. However, this drug showed a higher pKi value than amosulalol, HV-723, labetalol and ketanserin. On the other hand, the order of inhibition potencies for contraction of the rat aorta by phenylephrine was as follows: prazosin > tamsulosin > amosulalol > HV-723 > labetalol > ketanserin > clonidine > propranolol. Thus, although the affinity of tamsulosin to the α1B-AR subtype in the canine aorta was as high as that in the bovine prostate reported in our previous study, the affinity (pKi 7.87) of this drug to α1L-AR in the canine aorta was lower than that (pKi 8.99) in the bovine prostate. These observations suggested that the pharmacological potencies of tamsulosin in the aorta and prostate may be different.

1. The present study was designed to assess the displacement potencies of tamsulosin to 3H-prazosin bindings in two alpha1-adrenoceptor (AR) subtypes (alpha1H and alpha1L) in bovine prostate, rat heart and brain compared with those of amosulalol, labetalol, ketanserin, clonidine and propranolol. 2. The pKi values of tamsulosin to alpha1H and alpha1L subtypes in bovine prostate were 9.13 and 8.99 and these values were almost the same as those of prazosin. On the other hand, low pKi binding values of amosulalol, labetalol, ketanserin, clonidine and propranolol to these subtypes were observed. 3. Low pKi values of tamsulosin to alpha2- and beta-ARs and muscarinic and 5HT2 receptors in the rat brain were observed. 4. These results suggest that tamsulosin has high affinities to alpha1L-AR subtypes in bovine prostate and rat hearts as well as alpha1H-AR subtypes, implying an inhibitory effect of this drug on the contraction of the prostate.

The dissociating and/or residual inhibitory effects of bopindolol from β-adrenoceptors of atria strips pretreated with this drug which was then washed out with buffers on the responses to isoprenaline were determined and compared with those of propranolol, pindolol, atenolol, and the two active metabolites of bopindolol: 18-502 and 20-785. Low concentrations of bopindolol (10–9 to 10–8 mol/l) and the active metabolite 18-502 (10–9 mol/l) produced rightward shifts of the concentration-response curves. On the other hand, high concentrations of bopindolol (10–7 mol/l) and metabolite 18-502 (10–8 and 10–7 mol/l) produced a reduced maximum response by isoprenaline, suggesting that these nonparallel rightward shifts have pD2 values of 7.57 (bopindolol) and 7.67 (18-502), respectively, at 0 min after washout with buffers. Pindolol (10–7 mol/l) and propranolol (10–7 and 10–8 mol/l) also produced a rightward shift of isoprenaline response curves, and these concentration-response curves in guinea pig atria strips pretreated with pindolol (10–7 mol/l) and propranolol (10–6 mol/l) recovered to control levels. Neither of these drugs, however, reduced the maximum response by isoprenaline. A high concentration (10–5 mol/l) of atenolol was required for a rightward shift of the isoprenaline concentration-response curve, and this drug also did not reduce the maximum response. Thus, we conclude that bopindolol and metabolite 18-502 slowly dissociate and act as noncompetitive β-antagonists rather than easily reversible β-adrenoceptor antagonists.

This study was designed to further discriminate α1-adrenoceptor subtypes in rat aorta and prostate using functional experiments. Responses induced by phenylephrine were equilibrated in both tissues. The pA2 values and slope factors of several α1-antagonists were assessed using concentration-response curves. The antagonists used were prazosin, WB-4101, 5-methylurapidil (5-MU), HV-723, and tamsulosin. In addition, the effects of chloroethylclonidine (CEC) and nifedipine on phenylephrine-induced contractions were investigated. A high pA2 value for prazosin was observed in both tissues (aorta 9.84, prostate 9.19) and the ranking of each drug’s pA2 value is as follows: tamsulosin > prazosin > WB-4101 > HV-723 > 5-MU in the aorta, and tamsulosin > prazosin > 5-MU > WB-4101 = HV-723 in the prostate. A significant difference between the pA2 value of each drug except for tamsulosin in the aorta and in prostate was observed (p < 0.01). Inhibition of contraction by pretreatment with CEC was 83.9 ± 2.42% in the aorta, and 6.17 ± 0.94% in the prostate. On the other hand, inhibition of maximal response by pretreatment with nifedipine (1 µmol/l) was 35.1 ± 2.2% in the aorta and 24.5 ± 3.1% in the prostate. A good correlation between these pA2 values and pKi values for recombinant human α1b-adrenoceptor expressed in CHO cells (aorta) and α1a-subtypes of CEC pretreated rat hippocampus (prostate) were observed. In conclusion, these results suggest that: (1) the contraction of these two tissues is mediated by α1H-adrenoceptor with a high affinity for prazosin; (2) α1H-adrenoceptors correspond to α1b-(aorta) and α1a-subtypes (prostate), and (3) each α1-adrenoceptor subtype in the aorta and prostate may be α1b-(aorta) and α1a-subtypes (prostate), respectively.

The senescence-accelerated mouse (SAMP8) is a useful murine model of accelerated aging and learning deficiency. We examined bindings of [3H]pirenzepine, [3H]dizocilpine (MK-801), [3H]flunitrazepam, [3H]8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) and [3H]phorbol 12,13-dibutylate (PDBu) in SAMP8 brains, and compared them to those of SAMR1 (control). In the hippocampus of SAMP8 at 12 months, bindings of [3H]pirenzepine, [3H]MK-801, [3H]flunitrazepam, [3H]8-OH-DPAT and [3H]PDBu were significantly lower than those in SAMR1. In the cerebral cortex, bindings of [3H]pirenzepine, [3H]flunitrazepam and [3H]8-OH-DPAT were higher in SAMP8 than in SAMR1 at 12 months. [3H]PDBu binding was decreased in both the fractions of the membrane and cytosol in the hippocampus of SAMP8. The neurochemical findings presented here support behavioral and pharmacological findings that SAMP8 is a useful model of learning dysfunction and anxiety-deficiency. The usefulness of SAMP8 in studies on cognitive enhancers is also discussed.

Production of blood cells is regulated by the interplay of various cytokines and bone marrow stromal cells. Recently, a ligand for the orphan receptor Mpl was identified as thrombopoietin (TPO), which specifically regulates megakaryocyte differentiation, and it was reported to be expressed mainly in liver and kidney. As it was found that thrombopoietin is also produced in bone marrow stromal cells, we studied further the roles of bone marrow stromal cells on megakaryocytopoiesis and platelet formation. The stromal cells stimulated growth and maturation of bone-marrow-derived megakaryocytes in the presence of thrombopoietin, and also supported growth of BaF3 cells expressing exogenous Mpl without thrombopoietin. Thrombopoietin induces drastic morphological change of megakaryocytes in bone marrow cells in vitro, ie, the formation of lengthy beaded cytoplasmic processes (proplatelet formation). However, when the purified megakaryocytes were cocultured with the stromal cells with or without thrombopoietin, most of the megakaryocytes adhered to the stromal cells and remained unchanged, while free megakaryocytes induced proplatelet formation. These observations indicated that the stromal cells in a hematopoietic microenvironment in bone marrow secrete thrombopoietin and stimulate proliferation and maturation of megakaryocytes, but the interaction of megakaryocytes with the stromal cells may suppress proplatelet formation.

To clarify the physiological roles of muscarinic acetylcholine (mACh) receptor subtypes, M1 and M2, on learning and memory, we examined the effects of three antagonists, atropine (non-selective), pirenzepine (M1 selective) and 11-[[2-[(diethylamino)methyl]-1-piperidinyl]acetyl]-5, 11-dihydro-6H-pyrido[2, 3-b][1, 4]benzodiazepine-6-one, AF-DX 116 (M2 selective), on step-through passive avoidance tasks in mice. During acquisition tests, mice were trained repeatedly until they achieved criterion latency (300 s). In all experiments, drugs or vehicles were intracerebroventricularly administered. Pre-training (5 min before) administration of atropine (1-40 nmol) and pirenzepine(10 and 40 nmol) shortened the response latency in retention tests at 14 d after acquisition training. Pre-test (5 min before) and post-training (immediately after the acquisition training) administration of atropine slightly but not significantly impaired retention scores. The administration of AF-DX 116 did not apparently affect the scores in any of tests. Thus, the M1 receptor subtype coupling systems seem to be more important in the acquisition-consolidation process rather than in the retrieval process.

The effects of the chronic administration of bopindolol on the binding characteristics of [3H]CGP12177 and [3H]prazosin to cardiac α1H-, α1L-, β1- and β2-adrenoceptor subtypes of spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) were compared with those of two other β-blockers, atenolol and propranolol. Bopindolol (1 and 3 mg/kg/d), atenolol (50 mg/kg/d) and propranolol (60 mg/kg/d) were given to 10-week-old SHR for 12 weeks. The changes in Kd and Bmax values of the myocardium of SHR treated without and with those drugs were assessed by Scatchard analysis, and the ratio and Bmax values of the β1- and β2-adrenoceptor subtypes were also calculated from displacemental curves using ICI 118, 551. The systolic blood pressure in SHR was dose-dependently lowered by the administration of dopindolol, and was also lowered by the administration of atenolol and propranolol. The Bmax values of β1- and β2-adrenoceptors were lowered by the administration of bopindolol (1 and 3 mg/kg/d) without any changes in the Kd values or the ratio of β1- and β2-adrenoceptors. Propranolol lowered 3-fold the affinity to the β-adrenoceptor. On the other hand, the Kd and Bmax values of α1H- and α1L-adrenoceptor subtypes (high and low affinity binding sites for [3H]prazosin) were not changed by these drugs. These findings suggest that bopidolol had a beneficial effect on β-adrenoceptors in the membranes of cardiac muscles of SHR, simplying that these effects may contribute to lowering hypertension.

The senescence-accelerated mouse (SAM-P/8) is known as a murine model of aging and memory dysfunction. In the hippocampus and cerebral cortex of P/8, the contents of glutamic acid and glutamine were significantly higher than those of normal strain R/1 during 2 and 14 months. High K + -evoked endogenous glutamic acid release from the slices of P/8 was increased in comparison with R/1 at 9 and 11 months. In addition, the B max of [ 3 H]dizocilpine (MK-801, channel blocker for N- methyl- d -aspartic acid receptor/channel) binding in the cerebral cortex was age-dependently decreased in P/8 but not in R/1. These results suggest that synaptic dysfunctions in the glutamatergic system occur in the CNS of SAM-P/8.

Superoxide dismutase (SOD) activity,malondialdehyde (MDA) content and monoamine oxidase B (MAO-B) activity were measured in the brain, liver and kidney of a normal aging strain (R/1) and an accelerating aging strain (P/8) senescence-accelerated mice (SAM) at 9-10 months of age, and the effects of facteur thymique sérique (FTS) were examined. The activity of Cu,Zn-SOD in the kidney and MAO-B in the liver was significantly low and high in SAM-P/8 compared to SAM-R/1. FTS enhanced the activity of Mn-SOD and Cu,Zn-SOD in the kidney of SAM-P/8 and Cu,Zn-SOD activity in the brain of both SAM-P/8 and SAM-R/1. It decreased the activity of MAO-B in the liver and the contents of malondialdehyde (MDA) in the brain and kidney of SAM-P/8. Thus, FTS affects the biochemical factors related to senescence in SAM-P/8, a particular senescent animal model, and may thus possibly be effective as an anti-senescent medicine.

Bopindolol, a non-selective antagonist of beta 1- and beta 2-adrenoceptors (ARs), has been found by pharmacological, molecular biological techniques and molecular modeling to have several unique properties. Bopindolol produces sustained blockade of beta 1- and beta 2-ARs, has intrinsic sympathomimetic as well as membrane stabilizing actions, inhibits renin secretion, and interacts with 5-HT receptors. Also, our recent molecular modeling studies identified possible interaction sites between bopindolol and beta-AR subtypes. The reviewed studies support our findings that bopindolol is non-selective for beta 1- and beta 2-ARs, has low affinity for beta 3-AR subtype and has pharmacological properties that are likely to be beneficial in the treatment of cardiovascular diseases.

We investigated the characteristics of beta-adrenoceptors (beta-ARs) in rat white adipose tissues (WAT) with a radioligand receptor binding assay using (-)-[3H]-CGP12177. Scatchard analysis revealed that there are high- and low-affinity sites for (-)-[3H]-CGP12177 in WAT. The (-)-[3H]-CGP12177 bound to a high-affinity site was displaced by 1 microM propranolol. The rank of pKi values of catecholamines for the site was isoproterenol > epinephrine > norepinephrine. By contrast, BRL37344A, BRL35135A and SR59230A, beta 3-selective agonists had high affinity for the low-affinity site of (-)-[3H]-CGP12177, whereas (-)-[3H]-CGP12177 bound to a low-affinity site was completely displaced by 100 microM bupranolol but not 1 microM propranolol. The pKi values of the catecholamines (isoproterenol, norepinephrine, epinephrine) for this site were very low. In addition, the correlation between the pKi values of various beta-agonists for the low-affinity site of rat WAT and those obtained from rat cloned beta 3-ARs was significant, but those of human cloned beta 3-ARs were not. Consequently, the results suggested that the high- and low-affinity sites were beta 2-ARs and beta 3-ARs in rat WAT, respectively.

The senescence accelerated mouse (SAM) is known as a murine model of aging and memory dysfunction. In the cerebral cortical membranes of male 9-month-old SAM mice, the B max values of [ 3 H]rauwolscine and [ 3 H]nitrendipine binding, and the values of both K d and B max of [ 3 H]TCP binding in the accelerated aging strain SAM-P 8 were significantly increased compared with the values in the control strain SAM-R 1 . In hippocampal membranes, however, the B max values of [ 3 H]quinuclidinyl benzilate and [ 3 H]nitrendipine binding were significantly decreased in SAM-P 8 compared with those in SAM-R 1 . These results suggest that muscarinic acetylcholine receptors, α 2 -adrenoceptors, N- methyl- d -aspartate receptor channels and L-type Ca 2+ channels are changed in cerebral cortex and hippocampus in SAM-P 8 at 9 months.