Effects Of Alaproclate Research Articles

Investigation into the effects in-vitro of the 5-hydroxytryptamine reuptake inhibitor, alaproclate, on carbachol-stimulated inositol phospholipid breakdown in the rat cerebral cortex.

The effect of alaproclate in carbachol-stimulated inositol phospholipid (PI) breakdown in rat cerebral cortical miniprisms has been investigated. Carbachol-stimulated PI breakdown was greatly enhanced by increasing the assay potassium concentration from 5.88 to 18.2 mM. Alaproclate, on the other hand, did not influence carbachol-stimulated PI breakdown over the concentration range tested (0-100 microM) at either assay [K+]. The elution pattern of the inositol phosphates from the Dowex-1 columns was also unaffected by alaproclate both in the absence and presence of carbachol. Thus, the potentiation by alaproclate of tremor and salivation induced by the muscarinic agonist oxotremorine in-vivo reported previously is not seen when muscarinic function is measured in-vitro using carbachol-stimulated PI breakdown.

NMDA receptor-mediated increase in cyclic GMP in the rat cerebellum in vivo is blocked by alaproclate and GEA-857.

The effects of alaproclate and GEA-857 (2-(4-chlorophenyl)-1,1-dimethylethyl 2-amino-3-methylbutanoate) on the production of cyclic GMP in the rat cerebellum in vivo induced by stimulation of N-methyl-D-aspartate (NMDA) receptors were studied. Alaproclate per se at a dose of 20 mg/kg subcutaneously, did not influence the basal cGMP level. The increase in cGMP induced by harmaline (20 mg/kg subcutaneously) was dose-dependently antagonized by alaproclate (5-40 mg/kg subcutaneously). S-(-)-Alaproclate was 2-5 times more potent than the R-(+)-enantiomer. GEA-857 which in contrast to alaproclate is a very weak 5-HT uptake inhibitor shared the ability of alaproclate to inhibit the effect of harmaline on cGMP accumulation with similar potency to S-(-)-alaproclate. Alaproclate at 15 mg/kg subcutaneously blocked the increase in cGMP in cerebellum caused by NMDA itself at 200 mg/kg subcutaneously. In contrast to alaproclate, the K+ channel antagonist, 4-aminopyridine, 5 mg/kg subcutaneously, produced per se an increase in cGMP levels in the rat cerebellum by 300% which was antagonized by the NMDA receptor antagonists, dizocilpine, phencyclidine and (+/-)-CCP, the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester and by alaproclate. Alaproclate. Alaproclate and GEA-857 antagonized seizures induced by NMDA, 200 mg/kg subcutaneously at doses similar to those antagonizing the harmaline- and NMDA-induced elevation of cerebellar cGMP. Neither alaproclate nor GEA-857 caused any behavioural effects typical for uncompetitive NMDA receptor antagonists except a slight increase in motor activity and sniffing. The effect of alaproclate on the NMDA receptor-mediated increase in cGMP in rat cerebellum in vivo might be due to blockade of the cation channel of the NMDA receptor complex previously observed in in vitro experiments and these compounds seems to belong to the group of low-affinity uncompetitive NMDA receptor antagonists that might have clinical interest.

Alaproclate effects on voltage-dependent K + channels and NMDA receptors: Studies in cultured rat hippocampal neurons and fibroblast cells transformed with Kvl.2 K + channel cDNA

The effects of alaproclate on voltage-dependent K + currents and N-methyl- d-aspartate (NMDA) and ψ -aminobutyric acid A (GABA A) receptor currents were investigated in cultured rat hippocampal neurons using whole-cell voltage clamp recording techniques. Alaproclate produced a concentration-dependent block of the sustained voltage-dependent K + current activated by depolarization from −60 to +40mV (IC 50, 6.9μM). At similar concentrations alaproclate also blocked the sustained voltage-dependent K + current in fibroblast cells transformed to stably express Kvl.2 K + channels. Analysis of tail currents and the voltage-dependence of the alaproclate block suggested an open-channel blocking mechanism. Alaproclate also produced a potent block of NMDA receptor currents in hippocampal neurons (IC 50, 1.1 μM), but did not affect GABA A receptor currents (concentrations up to 100μM). The alaproclate block of NMDA receptors occurred predominantly by an open-channel mechanism, although the drug was also able to block closed NMDA channels at a much slower rate. The interaction of alaproclate with NMDA receptors (activated by 10 μM NMDA) appeared to be governed by a first order binding reaction with forward and reverse rate constants of 6.7 × 10 3M −1, and 0.025 sec −1, respectively (at −60 mV). At depolarized potentials the alaproclate-induced block of the NMDA receptor current was strongly reduced, a result opposite to that seen with the voltage-activated K + currents, suggesting that the K + channel block may occur at a superficial internal site, whereas the NMDA receptor block occurs at a deep external site. ( + )-Alaproclate was a more potent blocker of K + currents than (-)-alaproclate, whereas a reversed stereoselectivity was observed for NMDA receptor current, supporting the view that alaproclate block of the two channel types occurs at structurally distinct binding sites.

The effects of alaproclate and p-chlorophenylalanine on cued navigation performance in rats.

The present study investigates the effects of a serotonin (5-HT) reuptake inhibitor, alaproclate, on water maze cued navigation performance in serotonin depleted and control rats. Treatment with p-chlorophenylalanine (PCPA), a serotonin synthesis inhibitor, (400 mg/kg/day x 3 i.p.) significantly depleted cerebral levels of both 5-HT (about 80% depletion) and its major metabolite 5-HIAA (about 90% depletion) for at least 7 days. PCPA treatment also slightly decreased cerebral noradrenaline and dopamine levels (16% and 22% reductions, respectively). PCPA treatment alone had no effect on the acquisition of the cued navigation version (visible platform) of the water maze task measured as the distance to find the escape platform, but it significantly increased swimming speeds of the rats. Alaproclate (20 mg/kg i.p.) increased escape distance and slightly decreased swimming speeds of the rats. The effects of alaproclate did not differ between PCPA and sham treated (arabic gum 400 mg/kg/day x 3 i.p.) rats. The results demonstrate that alaproclate induced cued navigation behavioral deficit is maintained after a marked depletion of cerebral serotonin.

Alaproclate increases the excitability of hippocampal CA1 pyramidal cells and blocks the slow after-hyperpolarization.

Effects of alaproclate, an antidepressive substance and 5-HT uptake blocker, was studied using intracellular and extracellular recording techniques. Possible effects on the excitability of CA1 pyramidal cells in slices from rat hippocampus were explored. Alaproclate increased the probability of firing to an orthodromic input, increased the membrane resistance and prolonged the action potential. Increased excitability was also observed in extracellular recording experiments. It is suggested that these effects are due to depression of potassium channels in the membrane.

Effects of alaproclate, potassium channel blockers, and lidocaine on the release of 3H-acetylcholine from the guinea-pig ileum myenteric plexus.

The guinea-pig ileum longitudinal muscle-myenteric plexus preparation, preincubated with 3H-choline or 3H-noradrenaline, was mounted in an organ bath and superfused with Tyrode's solution. Alaproclate (2-(4-chlorophenyl)-1,1-dimethyl 2-aminopropanoate) (0.01-0.5 mmol/l) reduced (IC50 = 0.1 mmol/l) and at about 0.5 mmol/l completely blocked the electrically evoked 3H-acetylcholine secretion. The depressing effect of alaproclate (0.2 mmol/l) was not counteracted by atropine (0.01, 1 or 10 mumol/l), hexamethonium (0.1 mmol/l), phentolamine (1 mumol/l) yohimbine (1 mumol/l), haloperidol (1 mumol/l), 8-phenyltheophylline (10 mumol/l), cyproheptadine (1 mumol/l), metitepine (1 mumol/l), bicuculline (10 mumol/l), picrotoxinin (0.1 mmol/l), forskolin (25 mumol/l), 3-isobutyl-1-methylxanthine (5 mmol/l), nifedipine (1 mumol/l), verapamil (1 mumol/l), dilitiazem (1 mumol/l), high calcium (6 mmol/l), high potassium (10 or 15 mmol/l), tetraethylammonium (2 mmol/l), 4-aminopyridine (0.5 mmol/l), apamin (0.5 mumol/l), barium (0.5 mmol/l) or quinine (0.1 mmol/l). Among the potassium channel blockers tested only quinine (at 0.5 or 1 mmol/l), in the same manner as lidocaine, reduced the evoked secretion of 3H-acetylcholine. The results are in agreement with the hypothesis that the effect of alaproclate on the evoked 3H-acetylcholine secretion is not mediated by a neurotransmitter receptor, or a potassium channel sensitive to tetraethylammonium, 4-aminopyridine, apamin, or barium or quinine, but is due to a local anaesthetic effect. In contrast to the evoked secretion, the spontaneous release of 3H-acetylcholine was enhanced by high concentrations of alaproclate (0.4-1 mmol/l). The mechanism underlying the effect of alaproclate on the spontaneous release remains to be established. Alaproclate (0.25 or 0.5 mmol/l) also enhanced the spontaneous release and reduced the electrically evoked 3H-noradrenaline secretion.

Effects of alaproclate, oxotremorine and scopolamine on regional tissue levels of tachykinins and cholecystokinin in rat CNS

Effects of alaproclate, oxotremorine and scopolamine on regional tissue levels of tachykinins and cholecystokinin in rat CNS

Alaproclate Affects Membrane Ion Channels in GH3/B6 Pituitary Cells

Effects of alaproclate, an inhibitor of serotonin uptake, on the membrane of GH3/B6 clonal pituitary cells were studied using whole cell patch clamp recording techniques. Application of alaproclate (5 microM) depolarized the cell and increased the rheobase. Such treatment also increased the frequency of spontaneous firing. It is suggested that alaproclate decreases the potassium conductance in a manner similar to 4-aminopyridine and affects membrane calcium channels.

Alaproclate inhibits potassium currents and thereby enhances muscarinic stimulation in N1E-115 neuroblastoma cells

Effects of alaproclate, an inhibitor of the uptake of serotonin, on muscarinic cholinergic responses in N1E-115 neuroblastoma cells were studied using intracellular recording techniques. Application of carbachol activates an inward calcium channel, through an action on muscarinic receptors. The influx of calcium activates potassium channels. Alaproclate was found to block these potassium channels and thereby to prolong the muscarinic cellular response to carbachol. It is suggested that this is one mechanism by which alaproclate potentiates cellular responses to muscarinic cholinergic agonists.

Effects of subchronic treatment with imipramine, zimelidine and alaproclate on regional tissue levels of substance P-and neurokinin a/neurokinin B-like immunoreactivity in the brain and spinal cord of the rat

The effects of subchronic (14 day) treatment with the inhibitors at the uptake of monoamines, zimelidine, alaproclate and imipramine, on regional levels of substance P (SP) and other tachykinins in tissue in the central nervous system of the rat were studied by radioimmunoassay. In the ventral spinal cord, in which substance P is known to exist together with 5-hydroxytryptamine (5-HT), in the terminals of descending neurones, treatment with the selective inhibitors of the uptake of 5-HT zimelidine (2 × 10 μmol/kg p.o.) or alaproclate (2 × 10 μmol/kg or 2 × 20 μmol/kg) p.o.), increased the level of substance P-like immunoreactivity (SP-LI). The effect of alaproclate appeared to be dose-dependent. After treatment with imipramine (2 × 10 μmol/kg p.o.) only a tendency to increased levels of substance P-like immunoreactivity spinal cord was seen. Treatment with alaproclate, at the highest dose level, also elevated the concentration of neurokinin A/neurokinin B-like immunoreactivity (NKA/NKB-LI) in the ventral spinal cord. In the frontal cortex, in which separate monoaminergic and tachykinin-containing neurones interact, treatment with imipramine reduced the levels of SP-LI and NKA/NKB-LI, while treatment with alaproclate had the opposite effect. In the periaqueductal grey matter, treatment with zimelidine and alaproclate increased the levels of SP-LI and NKA/NKB-LI, while treatment with imipramine increased only the level of NKA/NKB-LI. In conclusion, subchronic treatment of rats with inhibitors of the uptake of monoamines induced changes in levels of tachykinin in frontal cortex, periaqueductal grey and spinal cord. The selective inhibitors of the uptake zimelidine and alaproclate, had similar effects on levels of tachykinin, while the inhibitor of the uptake of 5-HT and noradrenaline, imipramine induced changes in the frontal cortex, which were qualitatively different from the effects of zimelidine and alaproclate. Furthermore, the levels of different tachykinins were not always changed in parallel by the same treatment.

Effects of 5-hydroxytryptamine uptake blockers on the concentration in brain of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid in male rats, pro-oestrous rats and ovariectomized rats treated with oestrogen and progesterone.

The aim of this study was to determine the effect of 5-hydroxytryptamine (5-HT) uptake blockade on 5-HT turnover by measuring the concentrations of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in brain with the aid of high performance liquid chromatography and electrochemical detection. The indoleamines were measured in the anterior hypothalamus (AH), posterior hypothalamus (PH) and raphe nuclei 30 min after the i.v. injection of either alaproclate (30 mg/kg) or zimelidine (20 mg/kg). The effect of alaproclate was studied in male rats, pro-oestrous female rats, rats ovariectomized and injected s.c. with 20 micrograms oestradiol benzoate (OB) on dioestrus and at 12.00 h of the next day (presumptive pro-oestrus) with 2 mg progesterone (model 1) and rats ovariectomized 3-4 weeks before an s.c. injection of 20 micrograms OB followed 72 h later by an s.c. injection of 2 mg progesterone (model 2). Alaproclate caused a significant decrease in the 5-HIAA/5-HT ratio in the AH and PH of the brain of male rats, in the PH and raphe nuclei in pro-oestrous rats and model 1, and in the raphe nuclei alone in model 2. Zimelidine had no effect on the 5-HIAA/5-HT ratio in any area in model 2. In male rats the injection of parachlorophenylalanine produced a marked reduction in the brain concentrations of 5-HT and 5-HIAA, but the 5-HIAA/5-HT ratio was unchanged by a subsequent injection of alaproclate. None of the pharmacological agents affected significantly the brain concentrations of noradrenaline, dopamine or dihydroxyphenylacetic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of alaproclate on the pupillary responses to tyramine, phenylephrine and pilocarpine in depressed patients.

Nine depressed patients were treated with alaproclate, a selective 5-HT uptake inhibitor, for 3 weeks in a dose of 400 mg daily. The pupillary responses to tyramine, phenylephrine, and pilocarpine eye drops were measured on consecutive days before, after 1 week and after 3 weeks of treatment. The tyramine-induced mydriasis was unaffected by alaproclate, suggesting that it does not significantly inhibit the reuptake of noradrenaline. The pilocarpine-induced miosis and the phenylephrine-induced mydriasis were both enhanced after 1 week but not after 3 weeks of treatment. This suggests that alaproclate acutely increases the responsiveness of postsynaptic muscarinic and alpha 1 adrenoceptors.

Serotonergic potentiation of muscarinic agonist evoked tremor and salivation in rat and mouse.

The dose-effect of oxotremorine upon the onset, duration and magnitude of tremor and salivation was studied in both mice and rats. The threshold doses of oxotremorine (SC) for eliciting tremor were above 50 micrograms/kg in mice and above 150 micrograms/kg in rats and the threshold doses for eliciting salivation were above 75 micrograms/kg in mice and above 200 micrograms/kg in rats. Alaproclate, a nontricyclic 5-HT uptake inhibitor, when injected 30 min prior to the administration of the cholinergic agonist, produced a dose-dependent enhancement of tremor and salivation in both rats and mice. Alaproclate itself did not produce these effects in the absence of a muscarinic cholinergic stimulant such as oxotremorine, arecoline or the acetylcholine esterase inhibitor physostigmine. Both salivation and tremor could be fully blocked by atropine at any dose of the cholinergic stimulant and of alaproclate used. The potentiating effects of alaproclate on salivation and tremor could also be blocked by two serotonin receptor antagonists, metitepine and danitracen, but not by metergoline or cinanserin. Other compounds which inhibit the uptake of 5-HT such as fluoxetine, citalopram, norzimeldine, zimeldine and the non-tricyclic antidepressant, iprindol, did not enhance the cholinergic agonist induced tremor or salivation under the same conditions as did alaproclate. It is suggested that alaproclate exerts the potentiating effect at a hitherto undefined serotonergic receptor site.

Test-specific effects of the 5-HT reuptake inhibitors alaproclate and zimelidine on pain sensitivity and morphine analgesia.

The effects of the specific 5-HT uptake inhibitors alaproclate and zimelidine, the 5-HT releasing compound p-chloroamphetamine (PCA) and the specific NA uptake inhibitor desipramine on pain sensitivity were examined in male rats using the hot-plate and tail-flick methods. The effects of alaproclate and zimelidine on 5-HT uptake mechanisms in the hypothalamus and spinal cord were also studied. Alaproclate, zimelidine, PCA and desipramine produced hypoalgesia in the hot-plate but not in the tail-flick test. Naloxone (1 mg/kg) failed to block the hypoalgesia produced by alaproclate and PCA in the hot-plate test. Zimelidine but not desipramine pretreatment blocked the analgetic action of PCA in the hot-plate test. Alaproclate significantly enhanced morphine analgesia in the hot-plate test but did not affect morphine analgesia in the tail-flick test. In contrast, zimelidine tended to enhance and significantly prolonged morphine analgesia in the tail-flick test but did not affect morphine analgesia in the hot-plate test. Zimelidine inhibited 5-HT uptake with equal potency in the hypothalamus and spinal cord, while alaproclate produced a greater inhibition of 5-HT uptake in the hypothalamus. These findings show test-specific effects after enhancement of central 5-HT neurotransmission. It is suggested that various aspects of pain sensitivity and morphine analgesia may involve different 5-HT pathways in the brain and spinal cord. Moreover, 5-HT pathways in the forebrain may mediate analgesia of a non-opiate type.