Phenotypical Screening on Neuronal Plasticity in Hippocampal-Prefrontal Cortex Connectivity Reveals an Antipsychotic with a Novel Profile

Dysfunction in the hippocampus-prefrontal cortex (H-PFC) circuit is a critical determinant of schizophrenia. Screening of pyridazinone-risperidone hybrids on this circuit revealed EGIS 11150 (S 36549). EGIS 11150 induced theta rhythm in hippocampal slice preparations in the stratum lacunosum molecular area of CA1, which was resistant to atropine and prazosin. EGIS 11150 enhanced H-PFC coherence, and increased the 8−9 Hz theta band of the EEG power spectrum (from 0.002 mg/kg i.p, at >30× lower doses than clozapine, and >100× for olanzapine, risperidone, or haloperidol). EGIS 11150 fully blocked the effects of phencyclidine (PCP) or ketamine on EEG. Inhibition of long-term potentiation (LTP) in H-PFC was blocked by platform stress, but was fully restored by EGIS 11150 (0.01 mg/kg i.p.), whereas clozapine (0.3 mg/kg ip) only partially restored LTP. EGIS 11150 has a unique electrophysiological profile, so phenotypical screening on H-PFC connectivity can reveal novel antipsychotics.

Neuroprotective and anticonvulsant effects of EGIS-8332, a non-competitive AMPA receptor antagonist, in a range of animal models

BACKGROUND AND PURPOSE

Blockade of AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptors is a good treatment option for a variety of central nervous system disorders. The present study evaluated the neuroprotective and anticonvulsant effects of EGIS-8332, a non-competitive AMPA receptor antagonist, as a potential drug candidate.

EXPERIMENTAL APPROACH

AMPA antagonist effects of EGIS-8332 were measured using patch-clamp techniques. Neuroprotective and anticonvulsant effects of EGIS-8332 were evaluated in various experimental models, relative to those of GYKI 53405.

KEY RESULTS

EGIS-8332 inhibited AMPA currents in rat cerebellar Purkinje cells and inhibited the AMPA- and quisqualate-induced excitotoxicity in primary cultures of telencephalon neurons (IC(50)=5.1-9.0 microM), in vitro. Good anticonvulsant actions were obtained in maximal electroshock-, sound- and chemically-induced seizures (range of ED(50)=1.4-14.0 mg kg(-1) i.p.) in mice. Four days after transient global cerebral ischaemia, EGIS-8332 decreased neuronal loss in the hippocampal CA1 area in gerbils and rats. EGIS-8332 dose-dependently reduced cerebral infarct size after permanent middle cerebral artery occlusion in mice and rats (minimum effective dose=3 mg kg(-1) i.p.). Side effects of EGIS-8332 emerged much above its pharmacologically active doses. A tendency for better efficacy of GYKI 53405 than that of EGIS-8332 was observed in anticonvulsant tests that reached statistical significance in few cases, while the contrary was perceived in cerebral ischaemia tests.

CONCLUSIONS AND IMPLICATIONS

EGIS-8332 seems suitable for further development for the treatment of epilepsy, ischaemia and stroke based on its efficacy in a variety of experimental disease models, and on its low side effect potential.

Effects of EGIS-7625, a Selective and Competitive 5-HT2BReceptor Antagonist

Our aim was to specify the 5-HT(2) subtype selectivity of EGIS-7625 (1-benzyl-4-[(2-nitro-4-methyl-5-amino)-phenyl]-piperazine), a new 5-HT(2B) ligand, in receptor binding studies and characterize its pharmacology at 5-HT(2A), 5-HT(2B) and 5-HT(2C) receptors in in vivo experiments and in isolated organs, in vitro. EGIS-7625 had high affinity for recombinant human 5-HT(2B) receptors (pK(i) = 9.0) but much weaker affinity for 5-HT(2A) and 5-HT(2C) receptors (pK(i) = 6.2 and 7.7, respectively). In the classic 5-HT(2B) test, EGIS-7625 produced a concentration-related parallel rightward shift in the concentration-response relationship for the 5-HT-induced smooth muscle constriction in rat stomach fundus strips with a pA(2) of 9.4. On the other hand, EGIS-7625 was a weak competitive antagonist at 5-HT(2A) receptors as it shifted 5-HT-induced concentration-response curves to the right at high concentrations (pA(2) = 6.7) in rabbit pulmonary artery strips. The m-chlorophenylpiperazine-induced hypomotility and hypophagia was only partially attenuated by EGIS-7625 even at a dose of 30 mg/kg i.p. while mianserin, a non-selective 5-HT antagonist was almost fully effective in these tests at 3 mg/kg i.p., suggesting weak antagonistic effect of EGIS-7625 at neuronal 5-HT(2C) receptors, in vivo. In conclusion, EGIS-7625 is a potent, selective and competitive 5-HT(2B) antagonist that seems to be a good research tool for the separation of the functional roles of vascular 5-HT(2A) and 5-HT(2B) receptors.

Comparison of anticonvulsive and acute neuroprotective activity of three 2,3-benzodiazepine compounds, GYKI 52466, GYKI 53405, and GYKI 53655

GYKI 52466 [1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine], a non-competitive AMPA [alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate] and kainate receptor antagonist and its two analogues, GYKI 53405 [1-(4-aminophenyl)-3-acetyl-4-methyl-3,4-dihydro-7,8-methylenedioxy-5H-2,3-benzodiazepine] and GYKI 53655 [1-(4-aminophenyl)-3-methylcarbamyl-4-methyl-3,4-dihydro-7,8-methylenedioxy-5H-2,3-benzodiazepine] were investigated in two seizure models and in MgCl2 induced global cerebral ischaemia, as an acute neuroprotective model. The ED(50) values of GYKI 52466 for suppression of the tonic and clonic phases of sound-induced seizures were 3.6 and 4.3 mg/kg, respectively. The corresponding data for GYKI 53405 were 1.1 and 3.1 mg/kg, while ED(50) values of GYKI 53655 were 1.3 and 2.0 mg/kg, respectively. The inhibition of seizure evoked by maximal electroshock was also found to be remarkable: the ED(50) values of GYKI 52466 and its two analogues were 6.9, 2.6, and 2.2 mg/kg, respectively. All compounds prolonged the survival times in MgCl2 induced global cerebral ischaemia test in a dose-dependent fashion, with PD(50) (dose of 50% prolongation) values of 24.1, 8.3, and 8.2 mg/kg intraperitoneal, respectively. In audiogenic seizure model the duration of anticonvulsant action of 10 mg/kg GYKI 52466 and 5 mg/kg GYKI 53405, GYKI 53655 were examined, too. The effect of GYKI 52466 decreased to 50% after 2 h, while the analogues showed more than 80% seizure suppression 3 h after treatment. After 6 h the effect of GYKI 53655 decreased to zero, while the effect of GYKI 52466, remained on the 50% level.

Differential EEG effects of the anxiolytic drugs, deramciclane (EGIS-3886), ritanserin and chlordiazepoxide in rats

The influence of serotonergic and benzodiazepine type anxiolytic drugs on the cortical activation and sleep-wakefulness cycle were compared by evaluating the effects of ritanserin and deramciclane (EGIS-3886), two 5-HT2 receptor antagonists, and chlordiazepoxide on the electroencephalogram (EEG) in freely moving rats. Following drug administration (1, 3, and 10 mg/kg, PO for all drugs), EEG was continuously sampled for 6 h and power spectra were calculated for every 5 s to assess changes in slow wave activity and sleep phases. In a separate test, anticonvulsant effects of the drugs were examined in mice. Both deramciclane and ritanserin slightly increased total time spent in deep sleep (DS) and lengthened sleep episodes. In contrast, chlordiazepoxide had a strong inhibitory action on DS, sleep time being shifted to more superficial light sleep (LS). The incidence and length of the high voltage spindle (HVS) episodes characteristic for the motionless, awake rat were increased at the highest dose of both deramciclane and ritanserin, while it was decreased by chlordiazepoxide. In mice, chlordiazepoxide had a marked anticonvulsant effect, while deramciclane was moderately effective and ritanserin ineffective. In conclusion, the 5-HT2 receptor antagonist anxiolytic drugs seem to be superior compared to the benzodiazepine type anxiolytic drug, chlordiazepoxide, as ritanserin and deramciclane improved sleep quality by increasing sleep episode length and time spent in DS, while chlordiazepoxide enhanced sleep fragmentation and decreased DS.

Effect of deramciclane, a new 5-HT receptor antagonist, on cholecystokinin-induced changes in rat gastrointestinal function

Recent studies suggested that serotonin receptors may be involved in modulating the actions of cholecystokinin (CCK) in the gastrointestinal tract. The present work was designed to compare the effects of deramciclane, a recently developed serotonin-2 (5-HT2A/2C) receptor antagonist, and lorglumide, a CCK(A) receptor antagonist, on exogenous and endogenous CCK-induced pancreatic enzyme secretion and pancreatic growth, as well as on the emptying of the stomach and the gallbladder. Pancreatic secretory function was tested while CCK release was evoked by diversion of bile-pancreatic juice in rats. Adaptive growth of the pancreas was induced by chronic intragastric administration of camostate, a potent synthetic trypsin inhibitor in rats. Gastric emptying of a noncaloric test meal was investigated in response to intraduodenal intralipid infusion, also in rats. In fasted mice, gallbladder emptying was examined in response to intragastric egg yolk administration. In rats, diversion of bile-pancreatic juice from the duodenum stimulated pancreatic amylase secretion. This action was blocked by deramciclane and by lorglumide. Pancreatic hypertrophy and hyperplasia induced by chronic camostate administration was also suppressed by both the serotonin- and the CCK-receptor antagonists. Intraduodenal administration of intralipid induced a significant delay in gastric emptying. This effect was inhibited by both deramciclane and lorglumide in rats. In mice, intragastric administration of egg yolk elicited an accelerated release of bile from the gallbladder. Prior treatment with either deramciclane or lorglumide abolished this response. Lorglumide was able to inhibit the functional responses elicited by exogenous CCK administration in both pancreas, stomach and gallbladder, while deramciclane was not effective under such circumstances. Our data show that deramciclane inhibited the effects of CCK on pancreatic, gastric and gallbladder function when its endogenous release was stimulated, but did not alter the effects of exogenously administered peptide. These results suggest that serotonin, primarily via 5-HT2A receptors, may modulate CCK-mediated gastrointestinal functions in rats.

[Neurologic tests in children having recovered from leukemia]

56 long-term survivors of childhood ALL have been investigated with CT and neuro-psychological methods. At the CT examination we found that 45.4% of the cured patients had alterations. Short-term memory, attention, visual-motor coordination and IQ were found to be slightly impaired in this group. Nevertheless they didn't influence the social integration and educational achievement of long-term survivors of ALL.

Possible involvement of the dopaminergic system in the mode of action of the potential antidepressant trazium esilate

Trazium esilate (EGYT-3615) is structurally an as-triazino isoquinolinium salt which showed considerable activity in pharmacological tests characteristic for antidepressants (antagonism of tetrabenazine, potentiation of yohimbine, behavioral despair). The compound exhibited minimal sedative effect. Some findings suggest that it influences the central dopaminergic system. The drug potentiated actions of amphetamine such as stereotypy and hypermotility. It differentially blocked the hypothermic and the stereotypy inducing action of apomorphine. Trazium esilate also inhibited the cataleptic state provoked by bulbocapnine in mice. In higher dose it decreased the plasma prolactin level in rats. The compound potentiated the effect of norepinephrine on isolated vas deferens of the rat. Trazium esilate is a weak displacer on a1-, a2- and D2-receptors, however, it induced a2-receptor desenzitization after repeated treatment. It had no influence on rat brain cortical noradrenaline and striatal dopamine release evoked by high K+ concentration, but it increased the spontaneous dopamine outflow in rat striatum. The compound also elevated the striatal dopamine and DOPAC levels both after acute and chronic treatment.

EGYT-2509 a novel neuroleptic agent without extrapyramidal and endocrine side effects

The dibenzodioxazocine derivative EGYT-2509 was effective in neuropsychopharmacological tests characteristic for neuroleptics and antiparkinsonian drugs. It interacted with dopaminergic compounds similarly to chlorpromazine and haloperidol, but in certain tests it showed different activity. Similarly to chlorpromazine and haloperidol it inhibited the lethal effect of amphetamine in grouped mice. The apomorphine-induced stereotypy was potentiated by lower, and antagonized by higher doses of EGYT-2509. The compound did not show cataleptogenic activity and even antagonized the catalepsy evoked by bulbocapnine. The in vitro potency of EGYT-2509 to block dopamine-mediated inhibition of prolactin release was weaker by three orders of magnitude than that of haloperidol. In preliminary human studies it did not affect the plasma prolactin level. It is concluded that EGYT-2509 is a new potential antipsychotic agent with minimal risk of extrapyramidal and endocrine side effects.