In vivo bladder selectivity of imidafenacin, a novel antimuscarinic agent, assessed by using an effectiveness index for bladder capacity in rats

Imidafenacin (KRP-197) is a novel antimuscarinic agent for overactive bladder treatment. The inhibitory effect of imidafenacin on detrusor contraction has been adopted for assessing their bladder selectivity, but this is becoming less convincing as an effectiveness index. We, therefore, reevaluated the bladder selectivity of imidafenacin and other antimuscarinics using their effects on the bladder capacity as an effectiveness index. Bladder capacity was measured by intermittent cystometry in urethane-anesthetized rats. In the tissues related to antimuscarinic side effects, the inhibitory actions were measured each on salivary secretion by electrical stimulation of chorda tympani, on rhythmical contractions in colon, and on carbamylcholine-induced bradycardia. Imidafenacin, solifenacin succinate, tolterodine tartrate, and propiverine hydrochloride significantly increased the bladder capacity, with minimum effective doses of 0.003, 1, 0.03, and 3 mg/kg (i.v.), respectively. The antimuscarinics tested, except for propiverine hydrochloride, shared a common property of increasing bladder capacity at a dose which did not affect micturition pressure. The relative bladder selectivity of imidafenacin, solifenacin succinate, and tolterodine tartrate was 15-, 1.7-, and 2.5-fold higher over salivary gland; 150-, 1.9-, and 9.2-fold higher over colon; and 50-, 12-, and 4.6-fold higher over heart, respectively, than that of propiverine hydrochloride. Thus, imidafenacin shows the most highly selective for bladder over the tissues related to major antimuscarinic side effects, compared to the other three well-known antimuscarinics tested in the rat.

Ibudilast, a mixed PDE3/4 inhibitor, causes a selective and nitric oxide/cGMP-independent relaxation of the intracranial vertebrobasilar artery

Ibudilast, a mixed phosphodiesterase (PDE) 3/4 inhibitor, is a cerebral vasodilator widely used in Japan for treating post-stroke dizziness. However, little studies have been conducted on the vasorelaxant effects of PDE inhibitors in the vertebrobasilar artery associated with dizziness onset. The in vitro vasorelaxant properties of ibudilast were, therefore, investigated by comparing with known selective PDE inhibitors, using vertebrobasilar arteries. Vasorelaxant activities of PDE3, PDE4, PDE5 inhibitors, and ibudilast were assessed in 5-hydroxytryptamine precontracted ring preparations from rabbit intracranial and extracranial vertebrobasilar arteries. Ibudilast more selectively relaxed the intracranial than extracranial artery. Similarly, selective PDE3 and PDE4 inhibitors showed higher selectivity for intracranial arteries. Furthermore, like selective PDE4 inhibitor, the vasorelaxation by ibudilast accompanied by increase in cAMP levels was inhibited by the adenylyl cyclase inhibitor SQ22536 in intracranial arteries. Next, it was examined whether nitric oxide (NO)/cGMP signaling is involved in this vasorelaxation in intracranial arteries. The suppression of NO/cGMP signaling by an NO synthase inhibitor or a guanylyl cyclase inhibitor potentiated the vasorelaxion by a PDE3 inhibitor and reduced that by a PDE4 inhibitor, while either suppression of the signaling had little influence on that by ibudilast. These results suggest that ibudilast has the high vasoselectivity for intracranial artery based on a mixed PDE3 and PDE4-inhibition, and effectively relaxes intracranial arteries independently of NO/cGMP signaling because of its vasorelaxation compensated by either PDE3- or PDE4-inhibition depending on the state of NO/cGMP signaling change.

Design and synthesis of novel 7-heterocycle-6-trifluoromethyl-3-oxoquinoxaline-2-carboxylic acids bearing a substituted phenyl group as superior AMPA receptor antagonists with good physicochemical properties

We describe the design, synthesis, and physicochemical and biological properties of a novel series of 7-heterocycle-6-trifluoromethyl-3-oxoquinoxaline-2-carboxylic acids bearing a substituted phenyl group joined through a urethane or urea linkage to the heterocycle at the 7 position. Introduction of the trifluoromethyl group at the 6 position conferred good biological activity, including neuroprotective effects, as well as good physicochemical properties. In terms of alpha-amino-3-hydroxy-5-methylisoxazole propionate receptor (AMPA-R) affinity, a urea linkage was equivalent to a urethane linkage and a pyrrole ring at the 7 position reduced affinity in comparison with an imidazole ring. Among this series, compound 14h (KRP-199), which has a 4-carboxyphenyl group joined through a urethane linkage to a 7-imidazolyl heterocycle, was found to possess high potency and selectivity for the AMPA-R in vitro and to exhibit good neuroprotective effects in vivo. Furthermore, the compound showed good physicochemical properties, including stability to light and good solubility in aqueous solutions.

Neuroprotective effects of KCL-440, a new poly(ADP-ribose) polymerase inhibitor, in the rat middle cerebral artery occlusion model

It is reported that ischemic brain injury is mediated by the activation of poly(ADP-ribose) polymerase (PARP). In this study, we examined the pharmacological profile of KCL-440, a new PARP inhibitor, and its neuroprotective effects in the rat acute cerebral infarction model induced by photothrombotic middle cerebral artery (MCA) occlusion. In an in vitro study, KCL-440 exhibited potency with regard to inhibition of PARP activity, with an IC50 value of 68 nM. An in vivo pharmacokinetic study showed that the brain concentration of KCL-440 was sufficient to inhibit PARP activity during the intravenous infusion of KCL-440 at the rate of 1 mg/kg/h. KCL-440 at various doses or saline was administered for 24 h immediately after the MCA occlusion. Administration of KCL-440 led to a dose-dependent reduction in the infarct size at 24 h after MCA occlusion. Infarct sizes were 44.8% +/- 3.0% (n = 8), 40.5% +/- 1.1% (n = 8), 38.2% +/- 1.4% (n = 8), 35.1% +/- 2.1% (n = 8), 34.2% +/- 2.3% (n = 7), 32.6% +/- 1.9% (n = 8), and 31.0% +/- 2.1% (n = 5) at doses of 0, 0.01, 0.03, 0.1, 0.3, 1.0, and 3.0 mg/kg/h. When compared to the control group, a statistically significant difference was observed in the doses that were higher than 0.03 mg/kg/h. When the infusion of KCL-440 (1 mg/kg/h, n = 8) was started at 1 h after the MCA occlusion, a significant reduction in infarct size was observed; this was not observed when KCL-440 infusion was started 2 or 3 h after the MCA occlusion. Furthermore, increased poly(ADP-ribose) immunostaining was confirmed at the ischemic border zone 2 h after the MCA occlusion, and it was reduced by KCL-440 treatment. These results suggest that KCL-440 is a possible neuroprotective agent with high blood-brain barrier permeability and high PARP inhibitory activity.

Withdrawal from chronic morphine administration causes prolonged enhancement of immobility in rat forced swimming test

RATIONALE

Opiate-dependent subjects experience severe depression as one of the subjective symptoms during withdrawal. No experimental work, however, has focused on the ability of opiate-withdrawal to produce depression-like behavior in dependent animal. OBJECTIVES. We therefore investigated whether withdrawal from chronic morphine treatment affects immobility in forced swimming test in rats.

METHODS

Morphine was administered in a dose escalation fashion using doses ranging from 20 to 140 mg/kg twice daily for 14 days, followed by 1-6 days of withdrawal, and their duration of immobility was assessed.

RESULTS

After the last morphine treatment. an increase in immobility occurred late on day 3 and persisted to at least day 6 of withdrawal without any change in ambulatory activity.

CONCLUSIONS

The results suggest that the morphine withdrawal resulted in prolonged enhancement of depression-like behavior in drug-dependent laboratory animals.

Effects of indeloxazine HCl on kindled amygdaloid seizures in rats: comparison with the effects of phenytoin, diazepam, ethanol, and imipramine

The anticonvulsant effect of [(+/-)-2-[(inden-7-yloxy)methyl]morpholine (indeloxazine) HCl, a new cerebral activator, was investigated in rats against kindled seizures from the amygdala, an assumed model of secondarily generalized seizures in human. Indeloxazine (0.25-10 mg/kg, IP) dose-dependently depressed the kindled seizure and shortened the evoked amygdaloid afterdischarge. A high dose of indeloxazine (40 mg/kg, IP), however, induced generalized seizures. Comparison of the effects on the kindled seizures of indeloxazine to those of phenytoin, diazepam, ethanol, and imipramine revealed that the anticonvulsant actions of indeloxazine are similar to those of imipramine but not to those of phenytoin, ethanol, and diazepam. The results suggest that indeloxazine may exert its action through the monoaminergic system in the brain.

A new type of antiserum to thyrotropin-releasing hormone; detection of new TRH-immunoreactive cell groups in rat hypothalamus

We produced a new type of antiserum to thyrotropin-releasing hormone (TRH) in rabbits. The immunogen is TRH-BSA, the production of which is based on the formation of an amide bond using carbodiimide (EDC). The specificity of the antiserum was assessed by enzyme immunoassay (EIA) and immunohistochemistry. When using the anti-TRH serum for immunohistochemistry in rat hypothalamus, new magnocellular groups were detected in the ventrolateral parts of the posterior hypothalamus and the dorsal parts of the third ventricle. Colchicine treatment was found not to be necessary to visualize perikarya containing TRH.

A new dopaminergic terminal plexus in the ventral horn of the rat spinal cord. Immunohistochemical studies at the light and electron microscopic levels

It has been thought that the ventral motor column in the rat spinal cord is virtually free of dopaminergic fibers. However, a new dopaminergic terminal plexus was visualized at all spinal levels in the ventral horn using electron as well as light microscopic immunohistochemistry.