[The ability of NMDA glutamate receptor blockers to prevent a pentylenetetrazole kindling in mice and morphological changes in the hippocampus].

We investigated in mice the relationship between convulsions and morphological changes of hippocampal neurons that arise in the development of pentylentetrazol (PTZ)-induced kindling. The kindling was caused by of 35 mg/kg PTZ i.p. 3 times a week for a month. By the end of this period, 70% of the mice responded to the injections of PTZ with pronounced clonic or tonic-clonic seizures. The hippocampal slices (layer stratum pyramidale, CA1, Nissl's stain) obtained from mice exhibiting seizures revealed a large number of modified cells (24.7 +/- 2.1%). These hyperchromic neurons have been characterized by a decrease of the size cell body, there was a loss of turgor, the body cells shrink, and dendritic spines curl. Part of the cells took the shape of elongated neck. Such modified the dark type of neurons contained only 2.3 +/- 2.3% in the hippocampus of intact mice, and 30% of the mice resistant to the convulsive action ofPTZ during the period of observation. The expression of protein NeuN (Fox3) in hippocamal neuron including the hyperchromic once suggests that neurons on the whole did not die and were relatively viable. Preventive administration of NMDA receptor blockers (0.5 mg/kg, memantine 0.1 mg/kg or IEM-1958 1 mg/kg, s.c.) 30 minutes prior to PTZ reduced the proportion of mice which exhibited PTZ kindling from 70% to 40%. The modified neurons were observed in which the PTZ kindling due to the blocker presence did not develop, i.e., the same as in intact mice. Contrary, 24.0 +/- 5.6% of hyperchromic neurons were found in the hippocampal slices from mice manifested seizures, despite the co-administration of NMDA blockers. The data obtained indicate that modified neurons are the result of seizures suffered by the animals in the course of PTZ kindling, and that the blockade of NMDA glutamate receptors can suppress manifestations of seizures and the accompanying morphological changes of hippocampal neurons.

Involvement of ionotropic glutamate receptors in the appearance of arecoline tremor in mice.

Administration of the muscarinic cholinoreceptor agonist arecoline (6 mg/kg, s.c.) to mice induced long-lasting tremor. The ability of non-competitive antagonists of ionotropic glutamate receptors to suppress the onset of tremor was studied. These antagonists, i.e., adamantane and phenylcyclohexyl derivatives, selectively blocked NMDA-type receptor channels (monocations) or both NMDA-and AMPA-type channels (dications). Both types of blocker weakened arecoline tremor, though the dose-response relationships were different for mono-and dications. The effects of dications appeared only at low blocker doses (0.0001-0.01 micromol/kg) but gradually disappeared on dose elevation. These data lead to the conclusion that the mechanism of pathogenesis of arecoline tremor predominantly involves NMDA-type receptors. Moderate blockade of AMPA-type receptors could potentiate the preventive effect of mixed-action antagonists (anti-NMDA+anti-AMPA), though predominance of blocking action against AMPA-type receptors prevented this effect.

[Involvement of ionotropic glutamate receptors in the genesis of arecoline-induced tremor].

The muscarinic agonist arecoline (6 mg/kg, subcutaneously in mice) induced a long-lasting tremor. The inhibitory potency of non-competitive antagonists of ionotropic glutamate receptors has been studied. These antagonists are the derivatives of adamantane and phenylcyclohexyl. A part of them: monocationic compounds, selectively block the NMDA-receptor channels, their dicationic analogues affecting both channels of the NMDA- and the AMPA-glutamate receptors. Monocationic blockers effectively reduced the arecoline-evoked tremor and their potency correlated with ability to block the NMDA-receptor channels. Dicationic blockers revealed protective effect only in low range doses (0.0001-0.01 microM/kg). Further increase of the dose reduced or completely abolished this effect. This suggests that the NMDA-receptors are involved in the genesis of arecoline-evoked tremor. The only moderate blockade of the AMPA-receptors potentiates the drug blocking action but the prevalent blockade of these receptors impedes the effect on arecoline-evoked tremor.

Effects of ionotropic glutamate receptor channel blockers on the development of pentylenetetrazol kindling in mice.

Experiments on mice were performed to study the ability of monocationic and dicationic adamantane and phenylcyclohexyl derivatives to prevent the development of kindling induced by i.p. administration of pentylenetetrazol (Corasol, 35 mg/kg). The monocationic phenylcyclohexyl derivative IEM-1921 effectively slowed the development of kindling, this being seen over a wide range of doses (0.0001-0.1 micromol/kg). A monocationic adamantane derivative (memantine), also a selective non-competitive blocker of NMDA receptors, produced a similar effect at doses 100 times higher. The anticonvulsive activity of the dicationic phenylcyclohexyl derivative IEM-1925, which could block both types of glutamate receptors, differed from the activity of the monocationic derivative by having a more complex dose-response relationship. Thus, the development of kindling was suppressed by essentially the same doses as needed for the monocation IEM-1921 (0.001 micromol/kg). However, on reducing the dose by a factor of 10 (0.0001 micromol/kg), IEM-1925 facilitated the development of kindling. This difference in the prophylactic activities of selective NMDA receptor blockers and substances able to block both NMDA and AMPA receptors provides evidence that the mechanism of kindling involves both types of ionotropic glutamate receptor and the effects of compounds depend not only on the ratio of the contributions of these receptors, but also on the kinetic characteristics of the blocking action.

[Effects of blockade of ionotropic glutamate receptors on the development of pentylenetetrazole kindling in mice].

Effects of mono- and dicationic derivatives of adamantane and phenylcyclohexyl on the petyleneterazole-induced (35 mg/kg i. p.) kindling were studied in the experiments on mice. Monocationic derivative of phenylcyclohexyl IEM-1921, effectively retarded the development of kindling beginning the dose 0.0001 microM/kg. Memantine: derivative of adamantane (derivative of adamatane) produced the same effect with 100-fold increased dose. Dicationic derivative ofphenylcyclohexyl: IEM-1925, is able to block equally the open channels of both NMDA and subtype of Ca-permeable AMPA receptors. Its effect on kindling differed markedly from selective NMDA antagonists (IEM-1921 and memantine) in more complicated dose-dependence. The retardation of kindling IEM-1925 was induced at 0.001 microM/kg. On the contrary, a 10-time lower dose: 0.0001 microM/kg, facilitated the development of kindling. The observed difference in the activity of selective NMDA antagonists and the drugs combining anti-NMDA and anti-AMPA potency indicates that both types of ionotropic glutamate receptors are involved in the mechanism of petyleneterazole-induced kindling. The integral effect of channel blockade evoked by drugs seems to be dependent not only upon the ratio of the receptor types but on the kinetics of drug action, too.

Quest for agonist and antagonist selectivity at muscarinic receptors in guinea-pig smooth muscles and cardiac atria.

Potencies of 11 muscarinic agonists in eliciting contraction of smooth muscle in guinea-pig ileum, trachea, urinary bladder and uterus and in inhibiting the rate of contractions of cardiac atria were compared. While acetylcholine (ACh) was the most potent agonist on the ileum, uterus and cardiac atria, cis-L(+)-dioxolane was equally as potent as ACh on the ileum and more potent on the urinary bladder and trachea. Compared to ACh, methylfurmethide, oxotremorine, acetoxybut-2-inyl-trimethylammonium and cis-L(+)-dioxolane acted weakly on the atria. Aceclidine, arecoline and acetyl-beta-methylcholine displayed selectivity for the urinary bladder and pilocarpine for the tracheal and urinary bladder smooth muscles. Oxotremorine had very low activity on the uterus. The stereoselectivity of muscarinic ACh receptors (mAChRs) for cis-L(+)-and cis-D(-)-dioxolane was low in the urinary bladder and uterus and high in the ileum and trachea. Most antagonists showed little selectivity between different organs, but S(-)-phenylcyclohexylglycoloyl choline was 6 times more active on the urinary bladder than on the ileum and AF-DX 116 was 12-30 times more active on the atria than on the smooth muscles. Among the N-alkyl derivatives of benzilylcholine, the octyl derivative as 400 times more active on the ileum than on the atria, while among the N-alkyl derivatives of QNB, the N-decyl derivative was 41 times more active on the ileum. The observed differences in the potency of various agonists and their stereoisomers on different smooth muscles cannot be explained by differences in the accessibility of receptors or in receptor reserve.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of the neuromuscular blocking drug atracurium with muscarinic acetylcholine receptors.

On isolated rat heart atria, atracurium competitively antagonized the negative chronotropic effect of methylfurmethide, shifting the concentration-response curve to the right without diminishing the agonist's maximal effect; Kd calculated from dose ratios was 3.0 mumol/l. On the longitudinal muscle of rat ileum, atracurium antagonized the effect of methylfurmethide in a non-competitive manner; at 50 mumol/l atracurium, the maximum response to methylfurmethide was diminished by about 50%. Atracurium antagonized the binding of (3H)quinuclidinyl benzilate [3H)QNB) to muscarinic binding sites in the atria, ileal longitudinal muscle and cerebellum with IC50 values of 5-8 mumol/l, and in brain cortex of 25 mumol/l. Atracurium was little efficient, however, in antagonizing the binding of N-(3H-methyl) scopolamine [3H)NMS) to muscarinic binding sites. Complete blockade was not achieved at concentrations up to 1 mmol/l. Concentrations required to diminish the binding by 50% were 10 - 1000 times higher for (3H)NMS than for (3H)QNB. Atracurium brought about the dissociation of (3H)QNB-receptor complexes, but its effect was considerably stronger at a concentration of 30 mumol/l than at 1 mmol/l. Atracurium slowed down the dissociation of (3H)QNB-receptor complexes observed after the addition of atropine. The effects of atracurium on the dissociation of (3H)NMS-receptor complexes were similar to those on (3H)QNB-receptor complexes, but a high concentration of atracurium (1 mmol/l) produced a transient increase in (3H)NMS binding preceding its subsequent dissociation. Although the observations of the antagonism by atracurium of the effect of methylfurmethide on the heart atria, and of the inhibition of the specific binding of (3H)QNB to the atria, ileal smooth muscle, cerebellum and brain cortex are compatible with the assumption of a competitive interaction, the discrepancy between the effects of atracurium on the binding of (3H)QNB and (3H)NMS indicates that atracurium does not bind to the same binding site as (3H)QNB and (3H)NMS. It appears that most effects of atracurium on muscarinic receptors are allosteric and that both negative and positive cooperatives play a role in interactions between atracurium and muscarinic ligands.

[The peptide activator of cyclic nucleotide phosphodiesterases: its effect on muscle contractile activity]. / Peptid--aktivator fosfodiésteraz tsiklicheskikh nukleotidov: vliianie na sokratitel'nuiu aktivnost' myshts.

The presence of the peptide activator of cyclic nucleotide phosphodiesterase, which has been discovered previously in rat and calf myometrium, was studied in different rat tissues. The peptide was shown to present only in muscle tissues, except for intestinal tissue. In physiological experiments the peptide stimulated the contraction of rat uterine smooth muscle and diaphragmatic muscle. Phosphodiesterase inhibitors reduced this effect of the peptide. It is suggested that the effects of peptide are related to the changes in cyclic nucleotide levels in consequence of phosphodiesterase activation. Peptide did not change the activity of uterine adenylate cyclase.

A new non-depolarizing myorelaxant with high activity and specificity.

The curare-like activity and mode of action of tercuronium (p,p"-bistriethylammonium-p-terphenyl dibenzen-sulphonate) have been investigated in experiments with cats, rabbits, mice and pigeons as well as with rat phrenic diaphragm preparations. The curare-like activity of tercuronium was higher than that of tubocurarine and was close to that of pancuronium bromide. The curare-like activity of tercuronium was higher than that of tubocurarine and was close to that of pancuronium bromide. The neuromuscular blocking doses (ED95) of tercuronium, (+)-tubocurarine and pancuronium in cats, for example, were 0.08 microM/kg, 0.4 microM/kg and 0.04 microM/kg respectively. The time of development and duration of action were similar to those of (+)-tubocurarine and pancuronium. Tercuronium is a nondepolarizing myorelaxant. In experiments with cats the antagonism of neostigmine (0.1 mg/kg) to tercuronium was more pronounced than in the case of (+)-tubocurarine, pancuronium or gallamine. Tercuronium affected neither the arterial pressure nor the heart rate when given in neuromuscular blocking doses. Tercuronium did not block transmission through autonomic ganglia and had no atropine-like action. Only a 10-fold increase in the dose of tercuronium produced the ganglion blocking effect in cats. Under artificial respiration, cats and rabbits tolerated tercuronium in a dose 200 times exceeding its myoparalytic dose. It is concluded that tercuronium is distinguishable from (+)-tubocurarine by its high neuromuscular blocking activity as well as by its specificity and more pronounced neostigmine antagonism.

[Tercuronium, a new nondepolarizing myorelaxant with high activity and selective action]. / Terkuronii--novyi nedepoliarizuiushchii miorelaksant s vysokoi aktivnost'iu i izbiratel'nost'iu deistviia.

Tercuronium is p',p"-bis-triethylammonium-p-terphenyl dibenzosulfonate. As a curarelike agent tercuronium is 4--8 times as potent as (+)-tubocurarine. The time of the development and lasting of the blocking effect of tercuronium is approximately the same as that of (+)-tubocurarine. In a blocking dose tercuronium does not exert any effect either on the vegetative ganglia or arterial blood pressure. Partial blocking of the transmission through the vegetative ganglia as well as an insignificant and short-term drop of arterial blood pressure are recorded after intravenous injection of 10 myoparalytic doses of tercuronium. The antagonism of neostigmine against tercuronium was more pronounced than against (+)-tubocurarine, pancuronium and gallamine.

[Action of polymethylene-bis-quaternary compounds on the muscarinic and nicotinic cholinoreceptors]. / Deistvie nekotorykh polimetilen-bis-chetvertichnykh soedinenii na muskarinovye i nikotinovye cholinoretseptory.

The action of compounds with general formula (formula: see text) on the frog heart ventricle, cat blood pressure, guinea pig ileum and frog rectus abdominis was studied. With dioxolane radicals (type F-2268) a strong muscarinomimetic action on the cat arterial blood pressure and guinea pig ileum was observed, with maximum marked action at n = 10, which was more pronounced at an even than at odd number of methylene groups. On the frog heart the compounds with an odd number of "n" elicited an atropine-like action. The compounds with pentyl radicals produced no effect on blood pressure and a weak cholinolytic effect on the frog heart. On the ileum they exhibited a cholinomimetic effect. All compounds studied acted as noncompetitive cholinolytics on the frog rectus.