Site and mechanism of the colokinetic action of the ghrelin receptor agonist, HM01

BACKGROUND

It has been recently demonstrated that the ghrelin receptor agonist, HM01, caused defecation in rats that were treated to provide a model for the constipation of Parkinson's disease. HM01 significantly increased fecal output and increased Fos activity in neurons of the hypothalamus and hindbrain, but not in the spinal defecation center. Other ghrelin agonists act on the defecation center.

METHODS

Receptor pharmacology was examined in ghrelin receptor (GHSR1a) transfected cells. Anesthetized rats were used to investigate sites and mechanisms of action.

KEY RESULTS

HM01 activated rat GHSR1a at nanomolar concentrations and was antagonized by the GHSR1a antagonist, YIL781. HM01, intravenous, was potent to activate propulsive colorectal contractions. This was prevented by pelvic nerve section and by intravenous YIL781, but not by spinal cord section rostral to the defecation centers. Direct intrathecal application of HM01 to the defecation center at spinal level L6-S1 initiated propulsive contractions of the colorectum.

CONCLUSIONS & INFERENCES

HM01 stimulates GHSR1a receptors on neurons in the lumbosacral defecation centers to cause propulsive contractions and emptying of the colorectum. It has greater potency when given systemically, compared with other GHSR1a agonists.

New ghrelin agonist, HM01 alleviates constipation and L-dopa-delayed gastric emptying in 6-hydroxydopamine rat model of Parkinson's disease

BACKGROUND

Constipation and L-dopa-induced gastric dysmotility are common gastrointestinal (GI) symptoms in Parkinson's disease (PD). We investigated the novel ghrelin agonist, HM01 influence on GI motor dysfunctions in 6-hydroxydopamine (6-OHDA) rats.

METHODS

HM01 pharmacological profiles were determined in vitro and in vivo in rats. We assessed changes in fecal output and water content, and gastric emptying (GE) in 6-OHDA rats treated with orogastric (og) HM01 and L-dopa/carbidopa (LD/CD, 20/2 mg/kg). Fos immunoreactivity (ir) cells in specific brain and lumbosacral spinal cord were quantified.

KEY RESULTS

HM01 displayed a high binding affinity to ghrelin receptor (Ki: 1.42 ± 0.36 nM), 4.3 ± 1.0 h half-life and high brain/plasma ratio. 6-OHDA rats had reduced daily fecal output (22%) and water intake (23%) compared to controls. HM01 (3 and 10 mg/kg) similarly reversed the decreased 4-h fecal weight and water content in 6-OHDA rats. Basal GE was not modified in 6-OHDA rats, however, LD/CD (once or daily for 8 days) delayed GE in 6-OHDA and control rats that was prevented by HM01 (3 mg/kg acute or daily before LD/CD). HM01 increased Fos-ir cell number in the area postrema, arcuate nucleus, nucleus tractus solitarius, and lumbosacral intermediolateral column of 6-OHDA rats where 6-OHDA had a lowering effect compared to controls.

CONCLUSIONS & INFERENCES

6-OHDA rats display constipation- and adipsia-like features of PD and L-dopa-inhibited GE. The new orally active ghrelin agonist, HM01 crosses the blood-brain barrier and alleviates these alterations suggesting a potential benefit for PD with GI disorders.

Efficacy and safety of repeated dosing of netupitant, a neurokinin-1 receptor antagonist, in treating overactive bladder

AIM

NK-1 receptors in sensory nerves, the spinal cord and bladder smooth muscle participate in complex sensory mechanisms that regulate bladder activity. This study was designed to assess the efficacy and safety of a new NK-1 receptor antagonist, netupitant, in patients with OAB.

METHODS

This was a phase II, multicenter, double-blind study in which adults with OAB symptoms >6 months were randomized to receive 1 of 3 doses of netupitant (50, 100, 200 mg) or placebo once daily for 8 weeks. The primary efficacy endpoint was percentage change from baseline in average number of daily micturitions at week 8. Urinary incontinence, urge urinary incontinence (UUI), and urgency episodes were also assessed.

RESULTS

The primary efficacy endpoint was similar in the treatment groups (-13.85 for placebo to -16.17 in the netupitant 200 mg group) with no statistically significant differences between netupitant and placebo. The same was true for most secondary endpoints although a significant difference for improvement in UUI episodes and a trend for the greatest decrease in urgency episodes were seen in the netupitant 100 mg group. Netupitant was well tolerated with most treatment emergent adverse events (AEs) being mild. While the overall incidence of AEs increased with netupitant dose, there was no evidence for this dose dependency based on relationship to treatment, intensity, or time to onset.

CONCLUSIONS

The study failed to demonstrate superiority of netupitant versus placebo in decreasing OAB symptoms, despite a trend favoring netupitant 100 mg. There were no safety concerns with daily administration of netupitant over 8 weeks.

Effect of ghrelin and anamorelin (ONO-7643), a selective ghrelin receptor agonist, on tumor growth in a lung cancer mouse xenograft model

Purpose

Anamorelin (ONO-7643) is an orally active ghrelin receptor agonist in development for non-small cell lung cancer (NSCLC)-related anorexia/cachexia. It displays both orexigenic and anabolic properties via ghrelin mimetic activity and transient increases in growth hormone (GH). However, increasing GH and insulin-like growth factor-1 in cancer patients raises concerns of potentially stimulating tumor growth. Therefore, we investigated the effect of ghrelin and anamorelin on tumor growth in a murine NSCLC xenograft model.

Methods

Female nude mice (15–21/group) with established A549 tumors were administered ghrelin (2 mg/kg i.p.), anamorelin (3, 10, or 30 mg/kg p.o.), or vehicle controls daily for 28 days. Tumor growth, food consumption, and body weight were monitored. Murine growth hormone (mGH) and murine insulin-like growth factor-1 (mIGF-1) were measured in plasma.

Results

Tumor growth progressed throughout the study, with no significant differences between treatment groups. Daily food consumption was also relatively unchanged, while the percentage of mean body weight gain at the end of treatment was significantly increased in animals administered 10 and 30 mg/kg compared with controls (p < 0.01). Peak mGH levels were significantly higher in ghrelin- and anamorelin-treated animals than in controls, while peak mIGF-1 levels were slightly elevated but not statistically significant. All regimens were well tolerated.

Conclusions

These findings demonstrate that neither anamorelin nor ghrelin promoted tumor growth in this model, despite increased levels of mGH and a trend of increased mIGF-1. Together with anamorelin’s ability to increase body weight, these results support the clinical development of ghrelin receptor agonist treatments for managing NSCLC-related anorexia/cachexia.

Characterization of the effect of ganstigmine (CHF2819) on amyloid precursor protein metabolism in SH-SY5Y neuroblastoma cells

We have investigated the effect of ganstigmine (CHF2819), a novel geneserine derived acetylcholinesterase (AChE) inhibitor, on the expression and metabolism of the amyloid precursor protein (APP) in neuroblastoma cell line SH-SY5Y. The rationale was based on the suggestion that cholinergic activity may also be involved in the regulation of APP metabolism. We studied the acute effect on APP metabolism following the secretion of sAPPalpha in the conditioned medium of cells. Following short term treatment (2h), ganstigmine promoted a slight increase in the release of sAPPalpha, the maximal effect approaching on average 1.5 fold baseline value. The data obtained in the long term experiments demonstrate that continuous inhibition of AchE obtained with 100 nM ganstigmine following an exposure of 24 hours did not influence APP isoforms expression. However, the compound appeared to increase the constitutive release of sAPPalpha, with a mechanism that is derived from an indirect cholinergic stimulation.

Cyclodextrins in oligonucleotide delivery

The aim of this contribution is to summarize recent findings on the potential use of cyclodextrins and their derivatives as carriers for oligonucleotide agents. Their peculiar properties could be exploited in such an emerging therapeutic area by virtue of their capability of interacting with cellular membranes, thus giving rise to improved cellular uptake. In particular, some specific derivatives could be considered as promising future excipients for the delivery of "naked" antisense and/or decoy oligonucleotides which are difficult to formulate with existing pharmaceutical excipients.

Anticonvulsant preclinical profile of CHF 3381: dopaminergic and glutamatergic mechanisms

Following intraperitoneal or oral administrations, CHF 3381 ([n-(2-indanyl)-glycinamide hydrochloride]) protected rats against maximal electroshock (MES) test seizures. As glutamatergic pathways play a pivotal role in epilepsy, to better characterize the molecular mechanisms of action of CHF 3381, the drug effects on the binding of the excitatory amino acid antagonist [3H]-MK-801 in the presence of n-methyl-D-aspartate (NMDA), spermidine, or the combination of both ligands, were studied. CHF 3381 inhibited the [3H]-MK-801 specific binding in a noncompetitive fashion in respect to NMDA and polyamines recognition sites. CHF 3381 failed to change the kinetic characteristic of glycine B receptors labeled with [3H]-glycine; in contrast, it significantly increased K(d) values when the receptors were labeled with the more specific compound [3H]-MDL 105,519. CHF 3381 antagonized dopamine (DA)-induced behavioral responses and inhibited, in a glycine-dependent manner, the NMDA-induced [3H]-DA release from rat striatal slices, but it failed to change either the kinetic characteristics of D1, D2, or D3 receptors in synaptic plasma membranes (SPM) or the [3H]-DA uptake from striatal synaptosomes. Moreover, in primary cell cultures of cortical neurons, this drug exhibited glycine-independent neuroprotective effects against glutamate-induced excitotoxicity. It is concluded that this compound could have a potential use in several disease states where a pathological high level of NMDA receptor activation is thought to occur.

Effects of ENA713 and CHF2819, two anti-Alzheimer's disease drugs, on rat amino acid levels

The effects of oral ENA713 and CHF2819 (0.5, 1.5 and 4.5 mg/kg), two novel acetylcholinesterase inhibitors, on extracellular concentrations of amino acids in rat hippocampus, were evaluated using in vivo microdialysis. ENA713, at 4.5 mg/kg, but not CHF2819, significantly decreased glutamate, taurine, arginine and citrulline levels, without affecting aspartate concentrations. These results suggest that the modulation of amino acidergic transmission could represent an additional mechanism of action in Alzheimer's disease for some acetylcholinesterase inhibitors.

Preclinical Evaluation of CHF3381 as a Novel Antiepileptic Agent

CHF3381 [n-(2-indanyl)-glycinamide hydrochloride] has been selected on the basis of a screening program as the compound displaying the highest anticonvulsant activity in the maximal electroshock seizure (MES) test and the best therapeutic index with reference to the rotarod test in mice and rats. In this study, the antiepileptic activity and the behavioural toxicity of CHF3381 were characterised in multiple model systems. CHF3381 effectively prevented MES-induced convulsions when administered i.p. (ED50, 24 mg/kg and 7.5 mg/kg) or p.o. (ED50, 21 mg/kg and 21 mg/kg) in both mice and rats, respectively. The time course of oral anti-MES activity in the rat was related to the brain concentration profile of unchanged CHF3381. Interestingly, the brain drug levels were about 4-5 times higher than in plasma. CHF3381 was very effective in mice against picrotoxin-, and i.c.v. N-methyl-D-aspartate (NMDA)-induced hind limb tonic extension (ED50 Approximately/=10 mg/kg), but was a weaker antagonist of 4-amynopyridine- and bicuculline-induced tonic seizures (ED50 approximately/=100 mg/kg), and ineffective against pentylentetrazole- and picrotoxin-induced clonic seizures. CHF3381 antagonised the behavioural effects and lethality of i.p. administered NMDA (ED50 = 57 mg/kg p.o.), indicating that the compound may act as a functional NMDA antagonist. In keeping with this idea, CHF3381 weakly displaced [(3)H]-TCP from binding to NMDA receptor channels (Ki, 8.8 microM). In the rat amygdala kindling model, CHF3381 was more efficient against kindling development than against kindled seizures (minimally active dose = 80 vs. 120 mg/kg i.p). Furthermore, it significantly increased the seizure threshold in kindled rats at relatively low doses (40 mg/kg i.p.). In contrast with MK-801-induced hyperactivity, CHF3381 moderately reduced the spontaneous locomotor activity in mice at anticonvulsant doses. Toxic effects on motor performance (rotarod test) were found at high doses only (TD50 approximately/= 300 mg/kg p.o., congruent with 100 mg/kg i.p. in both mice and rats). Furthermore, CHF3381 did not impair passive avoidance and Morris water maze responding in the therapeutic range of doses. Finally, the development of tolerance after repeated doses was negligible. These data indicate that CHF3381 exerts anticonvulsant and antiepileptogenic effects in various seizure models and possesses good therapeutic window, with scarce propensity to cause neurological side-effects.

The neuroprotective activity of the glycine receptor antagonist GV150526: an in vivo study by magnetic resonance imaging

The neuroprotective activity of GV150526 (3-[2-(Phenylaminocarbonyl)ethenyl]-4,6-dichloroindole-2-carboxylic acid sodium salt), a selective glycine receptor antagonist of the NMDA receptor, has been evaluated by magnetic resonance imaging (MRI) in a rat model of middle cerebral artery occlusion. The aim of the work was to evaluate, using an in vivo method, whether GV150526 was able to reduce the extent of ischemic brain damage when administered both before and after (6 h) middle cerebral artery occlusion. GV150526 was administered at a dose of 3 mg/kg i.v. T2-weighted (T2W) and diffusion weighted (DW) images were acquired at 6, 24 and 144 h after the establishment of the cerebral ischemia. Substantial neuroprotection was demonstrated at all investigated time points when GV150526 was administered before the ischemic insult. The ischemic volume was reduced by 84% and 72%, compared to control values, when measured from T2W and DW images, acquired 24 h after middle cerebral artery occlusion. Administration of the same dose of GV150526, 6 h post-ischemia, also resulted in a significant (p < 0.05) neuroprotection. The ischemic volume was reduced by 48% from control values when measured from T2W images and by 45% when measured from DW images. No significant difference was found between volumes of brain ischemia obtained by either MRI or triphenyltetrazolium chloride staining. These data confirm the potential neuroprotective activity of the glycine receptor antagonist GV150526 when administered either before or up to 6 h after ischemia.

Biochemical and neurobehavioral profile of CHF2819, a novel, orally active acetylcholinesterase inhibitor for Alzheimer's disease

1,2,3,3a,8,8a-Hexahydro-1,3a,8-trimethylpyrrolo¿2,3-bĭndol-5-ol 2-ethylphenylcarbamate N-oxide hydrochloride (3aS-cis) (CHF2819) is a novel acetylcholinesterase inhibitor that produces central cholinergic stimulation after oral administration in rats. In vivo studies show that CHF2819 (0.5, 1.5, and 4.5 mg/kg p.o.) significantly increases acetylcholine levels in young adult rat hippocampus in a dose-dependent manner. Moreover, aged animals, which show a significant decrease in basal acetylcholine levels with respect to young adult rats, also exhibit a marked increase in the hippocampal concentrations of this neurotransmitter after the administration of CHF2819. This compound (1.5 mg/kg p.o.) significantly attenuates scopolamine-induced amnesia in a passive avoidance task. Furthermore, CHF2819 induces a significant decrease in dopamine levels and a significant elevation of extracellular concentrations of 5-hydroxytryptamine, whereas it does not modify norepinephrine and gamma-aminobutyric acid levels in the hippocampus of young adult rats. Functional observational battery screening demonstrates that CHF2819 (1.5 and 4.5 mg/kg p.o.) does not affect activity, excitability, autonomic, neuromuscular, and sensorimotor domains, as well as physiological end points (body weight and temperature). However, this compound induces involuntary motor movements (ranging from mild tremors to myoclonic jerks) in a dose-dependent manner. These findings suggest that the anti-amnestic properties of CHF2819, together with its stimulatory effect on cholinergic and serotonergic functions, might have a therapeutic potential mainly for the symptomatic treatment of Alzheimer's disease patients in which the cognitive impairment is accompanied by a depressive syndrome.

In vivo neurochemical effects of the acetylcholinesterase inhibitor ENA713 in rat hippocampus

Oral ENA713 (0.5, 1.5 and 4.5 mg/kg), an acetylcholinesterase inhibitor (AChEI), dose-dependently enhanced extracellular acetylcholine concentrations in the hippocampus of freely moving rats. This effect was paralleled by changes in both noradrenergic and dopaminergic transmission. In particular, ENA713 significantly decreased noradrenaline concentrations, whereas it significantly increased homovanillic acid levels, without affecting dopamine concentrations. Neither serotonin nor gamma-aminobutyric acid levels were modified by ENA713. These findings extend the neurochemical profile of ENA713 and suggest that it could be useful for the treatment of Alzheimer-type dementia which is associated with multiple neurotransmitter abnormalities in the brain.

4-Aminopyridine derivatives with antiamnesic activity

Acetylcholine (Ach) enhancement, useful in the treatment of Alzheimer's disease (AD), may be obtained by means of ion channel modulators such as 4-aminopyridine (4-AP). 4-AP is also the central ring of tacrine, the first drug approved for the treatment of AD. The synthesis and pharmacological activity of three 4-AP derivatives, prepared with the aim of improving their antiamnesic activity, is here described. In two of these compounds 4-AP is connected to 4-aminobutyric acid (GABA), whereas in the third it is connected to 2-indolinone, i.e., the skeleton of linopirdine, another Ach enhancing agent. The new compounds showed potent antiamnesic activity in comparison with piracetam.

Involvement of spinal NK1 and opioids receptors in modulating the inhibitory effect of capsaicin on micturition reflex in the acute spinalized guinea pig

PURPOSE

The aim of this work was to study the role of capsaicin-sensitive afferent fibers in modulating the micturition reflex at spinal level in urethane-anesthetized guinea pigs after spinal cord transection at level T3-T4.

MATERIALS AND METHODS

The intravesical effect of capsaicin was investigated in a series of cystometrograms performed in intact and spinalized animals.

RESULTS

In both intact and spinalized animals capsaicin, at 30 microM, induced a significant increase of volume threshold only, whereas at 100 microM it induced a complete inhibition of the spinal micturition reflex in 60% and 85% of the animals tested, respectively. This capsaicin inhibitory effect (CIE) was unaffected by intravenous phentolamine and propranolol (0.5 and 1 mg./kg., respectively), indomethacin at 100 nmoles intrathecally (i.t.), the CGRP receptor antagonist hCGRP8-37 (3 nmoles i.t.) and the NK2 receptor selective antagonist GR 94800 (1 nmol. i.t.). However, both naloxone (30 microg. i.t.) and the NK1 antagonist GR 82334 (10 to 20 nmoles i.t.) prevented CIE in the majority of spinalized animals.

CONCLUSIONS

These results suggest that CIE could be mediated by enkephalines released by dorsal root ganglion neurons through substance P release and subsequent activation of NK1 receptors in acutely spinalized guinea pigs.

Pharmacological characterization of thromboxane and prostanoid receptors in human isolated urinary bladder

1. Cumulative concentration-response curves (CRC) to prostaglandin E1 (PGE1), PGE2, PGD2 and PGF2alpha (0.01-30 microM) and to the thromboxane A2 (TXA2) receptor agonist U-46619 (0.01-30 microM) were constructed in human isolated detrusor muscle strips both in basal conditions and during electrical field stimulation. 2. All the agonists tested contracted the detrusor muscle. The rank order of agonist potency was: PGF2alpha > U-46619 > PGE2 whereas weak contractile responses were obtained with PGD2 and PGE1. Any of the agonists tested was able to induce a clear plateau of response even at 30 microM. 3. The selective TXA2 antagonist, GR 32191B (vapiprost), antagonized U-46619-induced contractions with an apparent pK(B) value of 8.27+/-0.12 (n = 4 for each antagonist concentration). GR 32191B (0.3 microM) did not antagonize the contractile responses to PGF2alpha and it was a non-surmountable antagonist of PGE2 (apparent pK(B) of 7.09+/-0.04; n = 5). The EP receptor antagonist AH 6809 at 10 microM shifted to the right the CRC to U-46619 (apparent pK(B) value of 5.88+/-0.04; n = 4). 4. Electrical field stimulation (20 Hz, 70 V, pulse width 0.1 ms, trains of 5 s every 60 s) elicited contractions fully sensitive to TTX (0.3 microM) and atropine (1 microM). U-46619 (0.01-3 microM) potentiated the twitch contraction in a dose-dependent manner and this effect was competitively antagonized by GR 32191B with an estimated pK(B) of 8.54+/-0.14 (n = 4 for each antagonist concentration). PGF2alpha in the range 0.01-10 microM (n = 7), but not PGE2 and PGE1 (n = 3 for each), also potentiated the twitch contraction of detrusor muscle strips (23.5+/-0.3% of KCl 100 mM-induced contraction) but this potentiation was unaffected by 0.3 microM GR 32191B (n = 5). 5. Cumulative additions of U-46619 (0.01-30 microM) were without effect on contractions induced by direct smooth muscle excitation (20 Hz, 40 V, 6 ms pulse width, trains of 2 s every 60 s, in the presence of TTX 1 microM; n = 3). Moreover, pretreatment of the tissue with 0.3 microM U-46619 did not potentiate the smooth muscle response to 7 microM bethanecol (n = 2). 6. We concluded that TXA2 can induce direct contraction of human isolated urinary bladder through the classical TXA2 receptor. Prostanoid receptors, fully activated by PGE2 and PGF2alpha are also present. All these receptors are probably located post-junctionally. The rank order of agonist potency and the fact that GR 32191B, but not AH6809, antagonized responses to PGE2 seem to indicate the presence of a new EP receptor subtype. Moreover, we suggest the presence of prejunctional TXA2 and FP receptors, potentiating acetylcholine release from cholinergic nerve terminals.

Middle cerebral artery occlusion alters neurotransmitter activities in ipsilateral and contralateral rat brain regions: an ex vivo voltammetric study

Differential pulse voltammetry with treated carbon fibre micro-electrodes has been successfully employed in in vivo analysis of neurotransmitter release and metabolism. This methodology has been now applied to ex vivo preparations (brain slices) in order to study diverse neurotransmitter activities in various brain regions ipsilateral and controlateral to a middle cerebral artery (MCA) occlusion performed in anaesthetised adult male rats. Data demonstrated that significant changes of voltammetric ascorbic acid levels related to the ischaemic state were monitored within the ipsilateral to MCA occlusion frontal cortex, striatum, nucleus accumbens and hippocampus which were the brain area studied. Furthermore, it appeared that voltammetric catecholaminergic and 5-hydroxy indolaminergic values measured within the nucleus accumbens controlateral to MCA occlusion differ significantly from the results monitored with the same technique in brain slices obtained from sham rats. In various studies, the brain regions contralateral to MCA occlusion are generally considered as control areas, however, the present data suggest that the nucleus accumbens contralateral to the MCA occlusion side is specifically affected by the ischaemic state.

Evidence against a permissive role of the metabotropic glutamate receptor 1 in acute excitotoxicity

Excitotoxicity has been proposed to contribute to neuronal loss in a broad spectrum of neurodegenerative conditions such as ischemia, hypoglycaemic coma or cerebral trauma. Excitotoxic neuronal injury appears to be mediated mainly by the over-activation of glutamate receptors, especially N-methyl-D-aspartate receptors, with subsequent excessive Ca2+ influx. Concurrent with the activation of glutamate-gated ion channels, metabotropic glutamate receptors (mGluR), which are G-protein coupled receptors, are also expected to be activated. Excessive stimulation of phospholipase C-coupled mGluR, mGluR1 and mGluRS, has been suggested to have neurotoxic consequences. However, the contribution of mGluR activation on excitotoxicity is still unclear and controversial. Here we report that, following ischemic and excitotoxic brain injuries, inactivation of mGluR1 does not prevent excitotoxic neuronal damage. Given the evidence that agonists at this group of mGluR promoted neuronal death in cerebrocortical cultures after oxygen-glucose deprivation or after N-methyl-D-aspartate exposure, our findings suggest that mGluR-mediated excitotoxicity is unlikely associated with mGluR1 but rather with other PLC-coupled mGluR.

The glycine antagonist GV150526 protects somatosensory evoked potentials and reduces the infarct area in the MCAo model of focal ischemia in the rat

The neuroprotective activity of the novel, selective glycine antagonist GV150526 was assessed in the middle artery occlusion (MCAo) model of focal ischemia. Postischemia administration of GV150526 (3 mg/kg i.v.) up to 6 h post-MCAo resulted in a significant reduction of the infarct volume measured histologically 24 h later. The neuronal protection by GV150526 was accompanied by functionally significant protection determined by somatosensory evoked potential (SEP) responses recorded from the primary somatosensory cortex of rats under urethane anesthesia. Experimental occlusion of the MCA 7 days prior to electrophysiological testing induced a clear reduction in the SEP amplitude. GV150526 (3mg/kg, i.v.) was able to protect SEP responses recorded from the hindpaw cortical field in two groups of animals treated either 1 (n = 9) or 6 h (n = 10) post-MCAo. SEP responses recorded from the forepaw cortical field, an area closer to the core of the ischemic damage, were significantly protected only in the group treated 1 h post-MCAo. Histological evaluation of the rat brain regions showed a correlated decrease in the ischemic area of GV150526-treated groups. The volumes of the ischemic brains of both GV150526 groups were statistically different from the MCAo group (P < 0.05). These findings demonstrate that GV150526 is able to prevent the ischemic damage assessed histologically and affect the functional correlates of the ischemia evaluated by the electrophysiological SEP measurements.

The microvascular system in ischemic cortical lesions

In the rat, normal blood flow can be restored in the territory of the occluded artery after an arterial occlusion. This event has been attributed to changes in the collateral vessels supplying the territory of the occluded artery. Since only a limited amount of data is available about the plasticity of the microvascular system after a cortical ischemic lesion, in the present study we have evaluated whether the restoration of blood flow to normal levels in the territory of the middle cerebral artery after permanent ischemia is due only to flow through preexisting collateral vessels or also to the development of new microvessels. Middle cerebral artery occlusion was performed in 45 rats. After 24 h of ischemia, magnetic resonance imaging was used to select 16 rats with cortical lesions of similar size and location. After 2 weeks, vascular corrosion casts were obtained from 8 rats by injection of low-viscosity resin and observed by scanning electron microscopy. A correlative light and electron microscopy study was performed using the remaining 8 rats. Two different patterns of vascular modifications were found, one dorsal and one ventral to the lesion. The dorsal portion of the lesion was vascularized by collateral arteries originating from the anterior or posterior cerebral arteries. Collateral trunks showed a meandering course, mainly in the occipital pole. In the ventral portion of the lesion a complex microvascular system was found characterized by an intense vascular proliferation. The arterioles showed a parallel, candelabrum-like pattern with dichotomic branching. Contraction rings were frequently seen. The capillaries showed a sinusoid-like structure, with a large lumen and a continuous endothelium with many micropinocytotic vesicles. A peripheral ring-shaped venous sinus was composed of a network of flat vessels. These results give the first comprehensive description of the microvascular modifications in a focal model of infarct and suggest that the restoration of blood flow to normal levels described in the territory of the middle cerebral artery after permanent ischemia may be due not only to flow through collateral vessels but also to the development of a new vascular system originating mainly from branches of the middle cerebral artery before the occlusion point.

Pharmacological characterization of tachykinin NK2 receptors on isolated human urinary bladder, prostatic urethra and prostate

The contractile effect of two highly potent, selective and peptidase-resistant neurokinin (NK) 1 and NK2 receptor agonists, namely delta-Aminovaleryl-[L-Pro9, N-MeLeu10]substance P-(7-11) (GR 73632) and [Lys3, Gly8-R-gamma-lactam-Leu9]NKA-(3-10) (GR 64349), respectively, was investigated on smooth muscle strips dissected from specimens of human detrusor, prostatic urethra and prostate. Furthermore, the potencies of two peptidic NK2 receptor antagonists, GR 87389 L 659,837, in antagonizing GR 64349-induced contractions were compared in these three tissues. In human detrusor muscle the rank order of agonist potency was: [beta Ala8 (NKA-(4-10)] > GR 64349 >> NKA-(4-10) >> SP = GR 73632 >> SP-methylester. The NK2 receptor antagonist, GR 87389, antagonized GR 64349-induced contractions in a competitive manner, whereas L 659,837 was a noncompetitive antagonist. In the prostatic urethra the rank order of agonist potency was GR 64349 > NKA-(4-10) > SP > GR 73632, whereas in the prostate it was: GR 64349 >> [beta Ala8 (NKA-(4-10)] > NKA-(4-10) > SP; GR 73632 was ineffective up to 30 microM. In the prostatic urethra and in the prostate GR 87389 was a noncompetitive antagonist with a potency similar to that exhibited in the detrusor. On the contrary, L 659,837 appeared to be a competitive antagonist in the prostate and in the prostatic urethra, having approximately the similar potency in these two tissues. The selective NK3 agonist senktide was ineffective up to 30 microM in all three tissues. These results are discussed in the view of the proposed NK2 receptor subtypes and considering possible therapeutic implications in the treatment of urinary bladder disorders.

Induction of NADPH-diaphorase activity in the rat forebrain after middle cerebral artery occlusion

Induction of NADPH-diaphorase (NDP) following ischemic infarction was studied by means of histochemistry in the rat cerebral cortex 1,2,7, and 14 days after distal occlusion of the right middle cerebral artery (MCA). The fine structure of cells in the penumbra region of the necrotic center was also investigated. MCA distal occlusion resulted in ischemic lesion of the frontoparietal cortex of variable extent; NDP induction was detected in neurons, astrocytes, macrophages, and endothelial cells, with regional specificity and a temporal gradient. One, two, and seven days after MCA occlusion, weak NDP positivity was consistently induced in some pyramidal neurons in cortical areas neighboring the necrotic area; NDP induction was also seen in pyramidal neurons of the ipsilateral anterior cingulate and infralimbic cortices and in the tenia tecta. In addition, numerous NDP-positive pyramidal neurons were detected in the contralateral frontoparietal cortex after relatively large ischemic lesions. Two weeks after MCA occlusion, NDP induction in neurons was only evident in the deep cortical layers near the lesion. NDP histochemistry combined with glial fibrillary acidic protein immunofluorescence, performed 7 days after MCA occlusion, indicated that the astrocytes at the periphery of the necrotic area were hypertrophic and some of them were also NDP-positive. One and two days after MCA occlusion, numerous macrophages displaying NDP positivity of variable intensity were seen at the periphery of the necrotic area and in the external capsule of the ischemic cerebral hemisphere. Many endothelial cells in the cortex and subcortical white matter were consistently NDP-positive in all rats. Electron microscopic studies indicated that the area adjacent to the necrotic center was composed of fibrous astrocytes, with the morphological characteristics of proliferation, and numerous lysosome-filled macrophages. Altogether the present results suggest that focal cerebral ischemia may induce in different cell types nitric oxide synthase, which is equivalent to NDP in fixed tissue. The induction of nitric oxide synthase may be related to (1) blood-flow regulation at relatively early postischemic stages, which may decline when collateral circulation is established, and/or (2) cytotoxic or neuroprotective mechanisms.

Evidence for the presence of both pre- and postjunctional P2-purinoceptor subtypes in human isolated urinary bladder

1. In order to characterize P2-purinoceptor(s) in human urinary bladder the contractile effects of ATP and its slowly-hydrolyzable analogues alpha, beta-methylene ATP (alpha, beta-MeATP) and beta, gamma-methylene ATP (beta, gamma-MeATP) were investigated on human detrusor strips taken from patients undergoing cystectomy for bladder carcinoma. 2. Serial concentration-response curves (SCRC) for ATP, alpha, beta-MeATP and beta, gamma-MeATP were constructed with an interval of 25 min between two successive doses to avoid tachyphylaxis. ATP (10 microM-10 mM) induced a phasic contraction, which was very rapid in onset. The dose-response curve to ATP appeared not to be monophasic: at the lower concentrations (10-300 microM) the curve was shallow, whilst at high concentrations (1-10 mM) the curve was steeper. The magnitude of the response obtained at the highest concentration tested (10 mM) was only 21.1 +/- 2.8% (mean +/- s.e. mean; n = 4) of the KCl (100 mM)-induced contraction. 3. alpha, beta-MeATP (0.3 microM-1 mM) and beta, gamma-MeATP (10 microM-1 mM) elicited a phasic contraction with a time course similar to that exhibited by ATP. The magnitude of the response obtained at the highest concentration tested (1 mM) was 70.3 +/- 6.3% for alpha, beta-MeATP (n = 10) and 27.9 +/- 4.5% for beta, gamma-MeATP (n = 8) of KCl (100 mM)-induced contraction. The rank order of potency was alpha, beta-MeATP > beta, gamma-MeATP > ATP. A plateau of response could not be achieved by any of these agonists. 4. The P2-purinoceptor antagonist, suramin (10-300 microM), dose-dependently antagonized only the lower part of alpha,beta-MeATP dose-response curve. Data were analysed in terms of dose-ratio estimated at two levels of response (10% and 35% of KC1 100 mM-induced contraction). At 10% of KCl response the Schild plot slope was 0.98 and the estimated pKB was 5.85, whereas using the dose-ratio at the 35% level of the KCl response, the Schild plot was not linear suggesting an interaction of alpha,beta-MeATP with a heterogeneous receptor population.5. The putative P2-purinoceptor antagonist, Coomassie Brilliant Blue G (CB-G) at 0.3 and 1 l micro M(n = 5), shifted to the left the alpha,beta-MeATP SCRC. The response at the highest concentration of agonist was potentiated, being equal to 78.8 +/- 11.7% of the KCl (100 mM) response (n = 5). CB-G at 0.3 microM also shifted to the left the beta,upsilon-MeATP SCRC and significantly potentiated the response at 1 mM up to 46.3 +/- 5.6% of KCl 100 mM response (n = 4).6. Pretreatment with terodotoxin (TTX) at 1 microM shifted to the left the alpha,beta-MeATP SCRC but the response to the highest concentration of the agonist was not potentiated, being 73.6 +/- 9.9% of the KCl(100 mM) response (n = 5). TTX (1 micro M) shifted to the left the beta,upsilon-MeATP SCRC and significantly potentiated the response at 1 mM (61.6 +/- 3.1% of KCl response; n = 4).7. The NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) at 100 micro M did not modify the SCRC to either alpha, beta or beta,upsilon-MeATP.8. We conclude that in human detrusor muscle there is a heterogeneity of purinoceptors. The complex antagonism exhibited by suramin suggests the presence not only of Ph-purinoceptors but also of another contractile P2-purinoceptor subtype insensitive to suramin. Moreover, the activity of CB-G and TTX seems to support the existence of a prejunctional P2-purinoceptor subtype inducing the release of one or more inhibitor neurotransmitters.

Overexpression of BCL-2 in transgenic mice protects neurons from naturally occurring cell death and experimental ischemia

Naturally occurring cell death (NOCD) is a prominent feature of the developing nervous system. During this process, neurons express bcl-2, a major regulator of cell death whose expression may determine whether a neuron dies or survives. To gain insight into the possible role of bcl-2 during NOCD in vivo, we generated lines of transgenic mice in which neurons overexpress the human BCL-2 protein under the control of the neuron-specific enolase (NSE) or phosphoglycerate kinase (PGK) promoters. BCL-2 overexpression reduced neuronal loss during the NOCD period, which led to hypertrophy of the nervous system. For instance, the facial nucleus and the ganglion cell layer of the retina had, respectively, 40% and 50% more neurons than normal. Consistent with this finding, more axons than normal were found in the facial and optic nerves. We also tested whether neurons overexpressing BCL-2 were more resistant to permanent ischemia induced by middle cerebral artery occlusion; in transgenic mice, the volume of the brain infarction was reduced by 50% as compared with wild-type mice. These animals represent an invaluable tool for studying the effects of increased neuronal numbers on brain function as well as the mechanisms that control the survival of neurons during development and adulthood.

A further analysis of the contraction induced by activation of cholecystokinin A receptors in guinea pig isolated ileum longitudinal muscle-myenteric plexus

The activity of a selective cholecystokinin (CCK)-A receptor agonist, N-acetyl derivative of A71623 (Ac-Trp-Lys(epsilon-N-[2-methylphenylamino-carbonyl]) -Asp-(NMe)Phe-NH2) was investigated in the guinea pig isolated ileum longitudinal muscle myenteric plexus. NAA caused both a phasic and tonic contraction at all concentrations tested (1-1000 nM). The selective CCK-A antagonist L-364,718 (Devazepide) antagonized both types of contraction with a pKB of 10.10 and 9.95, respectively. The CCK-B selective antagonist L-365,260 ((3R(+)-2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1, 4-benzodiazepine-3yl)-N-(3-methylphenyl)-urea) was inactive up to a concentration of 30 nM. Atropine at 300 nM and 1000 nM reduced the maximal response of NAA by only 17% and 50%, respectively. The selective neurokinin (NK)-1 antagonists GR 82334 ([D-pro9[Spiro-gamma-Lactam] Leu10, Trp11]-Phys (1-11)9) at 300 and 1000 nM and (+-) CP-96,345 [(2S, 3S)-cis- 2-(diphenylmethyl)-N- [(2-methoxyphenyl)-methyl] -1-azabici-clo [2.2.2]octan-3-amine] at 10 nM were inactive or partially active. When atropine and GR 82334 or (+/-) CP-96,345 were combined, they produced a dose-dependent synergistic inhibition of both phasic and tonic contractions induced by NAA. The selective NK-3 receptor agonist senktide induced both phasic and tonic contractions that were blocked by tetrodotoxin. In the presence of atropine and GR 82334, both 300 nM, a synergistic depression of the response to senktide similar to that observed for the agonist NAA was disclosed.(ABSTRACT TRUNCATED AT 250 WORDS)

ADP beta S induces contraction of the human isolated urinary bladder through a purinoceptor subtype different from P2X and P2Y

The classification of purinergic receptors is seriously hampered by the lack of specific antagonists. Furthermore, there is increasing evidence that other purinoceptor subtypes may exist that are different than the relatively well characterized P2X, P2Y, P2Z and P2T. Human isolated urinary bladder was reported to contract in response to challenge with alpha,beta-methylene adenosine 5'-triphosphate (alpha,beta-MeATP) and adenosine 5'-triphosphate (ATP), probably through activation of P2X purinoceptors. In this work, we tried to classify the purinoceptors subtypes present in human detrusor muscle by using adenosine 5'-[beta-thio]diphosphate (ADP beta S), alpha,beta-MeATP, 2-methylthio adenosine 5'-triphosphate (2-MeSATP), ATP and uridine 5'-triphosphate (UTP). We also examined the activity of two putative P2 antagonists (p-chloromercuribenzensulfonic acid [PCMBS] and Reactive Blue 2 [RB-2]). The agonist rank order of potency was alpha,beta-MeATP = ADP beta S > 2-MeSATP > ATP >> UTP. Cumulative responses to alpha,beta-MeATP induced a very rapid desensitization, but responses to alpha,beta-MeATP and ADP beta S, both at 100 microM, were additive. PCMBS antagonized ADP beta S-induced contractions with a pKB of 6.49, but it was inactive against alpha,beta-MeATP. The putative P2Y antagonist RB-2 had no effect against ADP beta S-induced contraction. We conclude that human detrusor muscle contains two contractile purinoceptor subtypes. One is activated by alpha,beta-MeATP and is probably the P2X subtype; the other is activated by ADP beta S and appears to be different from those accepted by the current classification. The similarity between our results and those obtained by other investigators is discussed.

Evidence for purinergic neurotransmission in human urinary bladder affected by interstitial cystitis

Detrusor specimens were obtained from 5 patients affected by interstitial cystitis (IC) and 5 patients with bladder carcinoma (controls). Muscle strips were prepared for in vitro pharmacological studies. In all detrusor strips taken from IC patients, an important portion of the electrically-induced contraction was atropine-resistant. In contrast, atropine-resistance was never observed in control detrusors. H1 and H2 antagonists did not affect noncholinergic contractile response which, conversely, was abolished following desensitization to alpha, beta methylene ATP (APCPP). Detrusor muscle from patients affected by IC exhibited an increase in sensitivity to APCPP and a decrease in sensitivity to acetylcholine with respect to control detrusor. Taken together these results are consistent with the presence of a purinergic neurotransmission in parasympathetic nerve terminals of the urinary bladder affected by IC, probably as a consequence of alterations in the innervation and/or electrical coupling between smooth muscle cells. The sensitivity of IC detrusor muscle to histamine was much lower than that of control detrusor, suggesting a desensitization of histamine receptors present in the bladder wall of IC patients.

Further studies on the effects of selective neurokinin agonists upon the activation of micturition reflex in rats. Evidence for a dual NK-1 receptor mediated excitatory and inhibitory activity

The ability of SP and some selective agonists for NK-1, NK-2 and NK-3 receptor subtypes to interfere with the micturition reflex after intra-arterial (i.a.) or intracerebroventricular (i.c.v.) administration was investigated in the urethane anaesthetized rat. When administered i.a. SP, the selective NK-1 agonist GR 73632 and the selective NK-2 agonists GR 64349 were equipotent to activate micturition reflex, both the tonic or rhythmic bladder contractions. GR 73632 but not GR 64349-induced activation of micturition reflex was antagonized in a dose-dependent manner by the selective NK-1 antagonist GR 82334. After i.c.v. administration SP, GR 73632 and the selective NK-1 agonist [Sar9,Met(0(2))11]-SP but not GR 64349 inhibited saline-induced activation of rhythmic bladder contractions; the order of potency was GR 73632 > [Sar9,Met(0(2))11]SP >> SP. Also the inhibitory effect of GR 73632 was dose-dependently affected by GR 82334. In the two models the selective NK-3 agonist senktide both after i.a. or i.c.v. administration induced neither excitatory or inhibitory activity. These findings suggest that neurokinins activate at the peripheral level the micturition reflex by an interaction at NK-1 and NK-2 receptor subtypes. In addition, NK-1 receptors appear to modulate, at the central level, the inhibition of the micturition reflex.

Analysis of the CCKB receptor antagonism of virginiamycin in guinea-pig ileum longitudinal myenteric plexus

1. Virginiamycin, a macrolide reported to bind selectively to CCKB/gastrin receptors has been studied in a functional test, namely cholecystokinin-induced contraction of guinea-pig ileum myenteric plexus (LMMP). 2. Virginiamycin (1-10 microM) antagonized the selective CCKB agonist cholecystokinin tetrapeptide (CCK-4). The antagonism appeared not to be competitive as the highest concentration (10 microM) caused a reduction of its maximal effect. An apparent pA2 of 6.64 +/- 0.06 (s.e.) could be estimated if this depression was ignored. The selective CCKB antagonist, L-365,260 (0.01-0.3 microM) antagonized competitively the CCK-4 induced contraction and a pKB of 8.60 +/- 0.16 (s.e.) was estimated. 3. The combined dose-ratio analysis for virginiamycin, tested at 3 and 10 microM in association with 0.03 and 0.1 microM L-365,260, respectively, resulted in observed log dose-ratios of 1.39 and 1.53. That was consistent with both antagonists acting on the same receptor in LMMP. 4. These data, represent the first evidence of the antagonism of virginiamycin in a functional assay and they support the hypothesis of homogeneity between CCKB receptors in the CNS and in peripheral tissues.

Evidence for two cholecystokinin receptors mediating the contraction of the guinea pig isolated ileum longitudinal muscle myenteric plexus

In guinea pig isolated ileum longitudinal muscle myenteric plexus, cholecystokinin octapeptide (CCK-8S) produced a rapid (phasic) contraction followed by a slower tonic phase. The tetrapeptide derivative CCK-4 and pentagastrin elicited only the phasic response up to 10(-6) M, whereas the tonic phase was also apparent at higher concentrations. The rank order of potency for the effect of agonists on the tonic and phasic responses were CCK-8S much greater than gastrin greater than CCK-8US congruent to pentagastrin greater than CCK-4 and CCK-8S greater than gastrin congruent to pentagastrin greater than CCK-4 greater than CCK-8US, respectively. Phasic responses of CCK-8S and CCK-4 were sensitive to atropine, whereas the tonic response could be completely abolished with the neurokinin-1 antagonist GR82334. The CCK-A receptor antagonist L-364,718 up to 10(-7) M had little effect on the phasic contracture of CCK-4. The CCK-B/gastrin receptor antagonist L-365,260 had no effect on the CCK-8S phasic response up to 10(-7) M, but antagonized the phasic response induced by low concentrations of CCK-4 in a competitive manner with an estimated pKB of 8.51. This value is close to that of 8.53 found in a guinea pig cortical binding assay. Both the second phase of the CCK-4 phasic concentration response curve (CRC) and the tonic contraction were insensitive to L-365,260.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacological analysis of 5-hydroxytryptamine effects on electrically stimulated human isolated urinary bladder

1. 5-Hydroxytryptamine (5-HT) is able to potentiate the contractions induced by electrical field stimulation of pieces of human isolated urinary bladder. On the basis of available selective 5-HT agonists and antagonists, we have further investigated the receptors involved and their site of action. 2. 5-HT produced a concentration-dependent increase of the contractile response to electrical field stimulation from 0.1 nM to 1 microM. At higher concentrations (up to 100 microM) the effect decreased. These activities were mimicked by a variety of 5-HT agonists, for which the following rank order of potency was found: 5-HT greater than alpha-methyl 5-HT greater than 5-methoxytryptamine greater than 5-carboxamidotryptamine greater than 2-methyl 5-HT much greater than GR 43175. In addition the gastro-prokinetics agents metoclopramide, cisapride and the 5-HT3 antagonist ICS 205-930 behaved as 5-HT agonists, their EC50 values being 2.3, 0.3, and 0.5 (microM) respectively. 3. The 5-HT potentiating effect was resistant to antagonism by ondansetron (1 microM) and cyanopindolol (1 microM), selective 5-HT3 and 5-HT1A/1B antagonists respectively. The 5-HT2 antagonists ketanserin (1 microM), spiperone (1 microM) and methysergide (1 microM) also showed a weak inhibitory activity. Methiothepin (0.1-1 microM) antagonized only the inhibitory effect of 5-HT. Metoclopramide (0.1-1 microM), cisapride (0.01-0.1 microM) and ICS 205-930 (0.3-3 microM) all produced a rightward displacement of the 5-HT response curve with concomitant reduction of the maximum response. The pA2 values calculated were 7.4, 8.5 and 7.0 respectively. The antagonism of metoclopramide was receptor specific and was not apparently related to interactions with dopaminergic activity since domperidone showed no antagonism of 5-HT, and metoclopramide, itself, did not antagonize the potentiating effect of prostaglandin F2a.4. The receptor involved in the potentiating effect of 5-HT may be located prejunctionally because 5-HT did not potentiate responses to acetylcholine (ACh) or electrical field stimulation with the parameters of direct muscle excitation. Also, since the 5-HT potentiating effect was blocked by atropine, it may be attributed to a release of ACh.5. This study suggests that in the human urinary bladder 5-HT causes two opposite effects on the contractile response to electrical field stimulation. A potentiating effect at low concentrations due to an interaction with an atypical receptor, different from the classical 5-HT1, 5-HT2 or 5-HT3 subtypes and an inhibitory effect at greater concentrations probably due to an interaction with 5-HT1-like receptors. The possibility that this atypical receptor possesses some characteristics of those found in other isolated preparations like guinea-pig ileum, rat oesophagus and mouse embryo colliculi neurones is discussed.

Antispasmodic effects of flavoxate, MFCA, and REC 15/2053 on smooth muscle of human prostate and urinary bladder

The antispasmodic effects of the flavone compounds flavoxate hydrochloride, 3-methylflavone carboxylic acid (MFCA), and REC 15/2053 (and in the case of the detrusor, oxybutynin), on the human detrusor, prostatic adenoma, prostatic capsule, and bladder neck, were studied by the in vitro isometric method. All the compounds inhibited, in different orders of potency, potassium-induced contractions of the tissues. Flavoxate showed a slightly greater activity than the other two compounds in the prostatic and bladder neck tissues. However, REC 15/2053 displayed greater activity in the detrusor than in the other tissues. The relaxant effect on the prostatic tissues suggests a potential use for these compounds in benign prostatic obstruction.

Effects of some antidepressants on the volume-induced reflex contractions of the rat urinary bladder: lack of correlation with muscarinic receptors affinity

It has been suggested that tricyclic antidepressants such as imipramine, might exert their anti-enuretic action by a blockade of muscarinic receptors in the detrusor muscle of the urinary bladder. We have therefore investigated the effects of two tricyclic (imipramine and nortriptyline) and three atypical (citalopram, amineptine and mianserin) antidepressants on the micturition reflex and muscarinic receptors in rats. The micturition reflex pathway was monitored indirectly by recording the rhythmic intravesical pressure waves which occurred when the bladder was distended and maintained under constant saline-volume. The activity of the antidepressants was correlated to their potencies as antagonists of [3H]QNB binding to rat brain (mainly M1 receptors) and bladder (mainly M2 receptors) membranes, as well as antagonists of carbachol-induced contractions of rat bladder strips. Only imipramine and citalopram dose dependently inhibited the voiding contractions, whereas nortriptyline, imipramine and mianserin (in order of potency) were active both in binding studies and as competitive antagonists of carbachol-induced bladder contractions, but were inactive in inhibiting the micturition reflex. The present data seem to suggest that affinities for muscarinic receptors are unrelated to the inhibition of micturition reflex.

Receptor binding studies of the flavone, REC 15/2053, and other bladder spasmolytics

The new flavone derivative REC 15/2053, a compound with spasmolytic activity on the lower urinary tract, was examined for its in vitro interaction with alpha- and beta-noradrenergic receptors, dopaminergic, muscarinic, serotoninergic, and opiate receptors, and calcium-channel binding sites labeled with 1,4-dihydropyridines from normal rat brain. All the investigated receptors are directly or indirectly involved in the nervous control of the lower urinary tract functions. The activity of REC 15/2053 on these receptors was studied in comparison to the most common drugs used in the management of urinary bladder disorders such as flavoxate, emepronium bromide, oxybutynin, terodiline, and imipramine. REC 15/2053 showed only weak binding to [3H]nitrendipine sites (IC50 = 14 microM) and muscarinic receptors (IC50 = 18 microM), whereas flavoxate was slightly active only at muscarinic receptors (IC50 = 12.2 microM). Emepronium bromide, oxybutynin, and terodiline were active only at muscarinic receptors, with IC50 values of 236, 5.4, and 588 nM, respectively. Oxybutynin showed a weak affinity to [3H]nitrendipine binding sites (IC50 = 44.4 microM). Imipramine was active at alpha 1-adrenergic and muscarinic receptors (IC50 = 248 and 653 nM, respectively). The activity of REC 15/2053 at muscarinic receptors and 1,4-dihydropyridine binding sites seems too low to account for its mechanism of action.

Pharmacological activities of the main metabolite of flavoxate 3-methylflavone-8-carboxylic acid

The pharmacological properties of 3-methylflavone-8-carboxylic acid (MFCA), the main metabolite of flavoxate, have been studied in vitro and in vivo. MFCA did not display antispasmodic activity on isolated organs contractions induced by histamine, acetylcholine or CaCl2, nor did it exhibit significant affinity for the rat brain alpha- and beta-adrenergic, serotoninic, muscarinic, D2, opiate and Ca2+ receptors. However, it showed a remarkable phosphodiesterase (PDE) inhibiting activity. Moreover in vivo studies indicate an interesting activity of MFCA which inhibited the rat urinary bladder voiding contractions, increased bladder volume capacity and decreased micturition pressure in the rat cystometric recordings. The activity of MFCA in the two in vivo experimental models, probably related to cAMP-PDE inhibitory properties, suggests that flavoxate's therapeutical potential might be partially sustained by its main metabolite.