Rat mesencephalic neuronal cells cultured for different periods as a model of dopamine transporter ontogenesis.

Ventral mesencephalic neurons contained only low-affinity and sodium-independent binding sites of [3H]WIN 35,428 (marker of dopamine transporter) during the first 10 d in primary cultures. These sites were present in cytosol, and they are not very probably related to dopamine transporter. After 12 d in culture, membrane-bound, high-affinity, and sodium-dependent [3H]WIN 35,428 binding sites were detected. In membranes prepared from cells 14 d in culture, cocaine displaced [3H]WIN 35,428 binding with similar potency to that in striatal membranes of adult rat brain. The high-affinity [3H]WIN 35,428 binding sites in mesencephalic neuronal cell cultures are very probably related to dopamine transporter. The development of high-affinity [3H]WIN 35,428 binding sites in neurons cultured for different time periods could be a useful model of dopamine transporter ontogenesis.

Comparison of [3H]WIN 35,428 binding, a marker for dopamine transporter, in embryonic mesencephalic neuronal cultures with striatal membranes of adult rats.

In contrast to striatal membranes of adult rats, where high- (KD1 = 34 nM) and low- (KD2 = 48,400 nM) affinity binding sites for [3H]WIN 35,428 are present, in primary cultures of ventral mesencephalon neurons (CVMNs) only low-affinity binding sites were found (KD = 336,000 nM). The binding of [3H]WIN 35,428 in CVMNs prepared from rat embryos was reversible, saturable, and located in cytosol. Although dopamine (DA) uptake blockers inhibited [3H]DA uptake at nanomolar concentrations in CVMNs, the displacement of [3H]WIN 35,428 binding in CVMNs by DA uptake inhibitors required 100-8,000 times higher concentrations than were needed to displace [3H]WIN 35,428 binding in striatal membranes. Piperazine derivatives, e.g., GBR-12909, GBR-12935, and rimcazole, inhibited [3H]WIN 35,428 binding in CVMNs more effectively than did cocaine, WIN 35,428, mazindol, nomifensine, or benztropin. A positive correlation (r = 0.779; p < 0.001) was found between drug affinities for the striatal membrane sites labeled by [3H]WIN 35,428 and their abilities to inhibit DA uptake in CVMNs, whereas no correlation existed between the IC50 values of drugs that inhibited [3H]WIN 35,428 binding and [3H]DA uptake in CVMNs. The cytosolic [3H]WIN 35,428 binding sites may be a piperazine acceptor and may not be involved in the regulation of the DA transporter.

[Possibilities of therapeutic applications of neuronal calcium homeostasis]. / Moznosti terapeutického vyuzití zásahu do neuronální kalciové homeostázy.

The role of calcium as a second messenger which mediates the transmission of the signal and has an impact on cellular regulation of the majority of organs at all stages of development was confirmed during the past decade. In the submitted review the authors summarize mechanisms by which calcium exerts its regulatory function. At the same time the authors discuss the possible ratio of disorders in the above systems in various diseases in particular those of the central nervous system and possible pharmacotherapeutic interferences at different levels of transmission of the signal mediated by calcium. As in the mentioned area at the clinical level so far mainly calcium channel blockers were used, the authors summarize the use of these substances in the treatment of cerebral ischaemia, migraine, epilepsy and manic-depressive disease.

[What is next in the development of antidepressives?]. / Jak dál ve vývoji antidepresiv?

After some findings concerning the mode of action of antidepressants, it was possible to hypothesize the molecular basis of depressive disorders (monoamine hypothesis, receptor hypothesis). These informations made the preparation of drugs acting by a completely new mechanism. Possible an antidepressant effect was observed after the administration of GABA-ergic agonists, or agents influencing dopaminergic transmission, S-adenosylmethionine, and drugs influencing second messenger systems. As a consequence of these findings, the GABA-ergic hypothesis, hypothesis of endogenous ligand (barinine hypothesis is discussed in more detail), and second messenger hypothesis of affective disorders were formulated. Agents influencing second messenger systems and S-adenosylmethionine seem to be a promising field of future investigation.

[A comparative pharmacologic study of histamine H-1 antagonists]. / Farmakologická srovnávací studie histaminových H1-antagonistu.

In a representative group of 10 conventional antihistaminic agents, a comparison of their H1-antagonistic efficacy was carried out in a series of pharmacological tests. A very good correlation of findings obtained under in vivo conditions in guinea-pigs (tests of detoxication of histamine and histamine aerosol) and a test in rats, which examined the influence on local changes induced by histamine in the dermal region, was demonstrated. No statistically significant correlation of in vivo findings and receptor binding studies on membranes of the rat brain (displacement of (3H)-mepyramine) was found. The tests based on displacement of (3H)-mepyramine are usable primarily for the needs of screening research. The predictive value of pharmacological findings obtained under in vivo conditions is substantially higher.

Binding characteristics of the dopamine agonist/antagonist [3H]terguride (transdihydrolisuride) in the rat striatum.

The binding properties of [3H]terguride were studied in various regions of the rat brain. The highest density of [3H]terguride binding sites was found in the striatum and tuberculum olfactorium. In the striatum, the binding was saturable, stereoselective and of a high affinity. There was a good correlation between the inhibition of [3H]terguride and [3H]spiperone bindings by various dopaminergic agents. Drugs with affinity to another type of receptors did not displace [3H]terguride binding in the striatum; only SCH 23390 was effective. The experiments indicate a certain affinity of the ligand to D-1 receptors. Nevertheless, [3H]terguride appears to have an affinity to D-2 receptors in the striatum and, thanks to its dopamine agonistic/antagonistic profile, would be useful in the further study of dopamine receptors.

The use of striatal dopaminergic supersensitivity for the evaluation of drugs with possible antidyskinetic properties.

An animal model of tardive dyskinesia was used for the evaluation of potential antidyskinetic properties of the neuropeptide L-Prolyl-L-Leucyl-glycinamide (PLG) and related drugs: cyclo[glycine-(1-amino-1-cyclopentane) carbonyl]--c(CPC-Gly) and cyclo[alanine-(1-amino-1-cyclopentane) carbonyl]--c(CPC-Ala). Dopaminergic supersensitivity was induced by repeated administration of the neuroleptic drug isofloxythepin. Isofloxythepin (5 mg/kg/day po) after the withdrawal increased Bmax of 3H-spiperone striatal binding sites, significantly decreased HVA level in the striatum and induced tolerance to the cataleptic effects challenged by perphenazine. PLG, c(CPC-Gly) and c(CPC-Ala) counteracted supersensitive responses of isofloxythepin. The use of c(CPC-Gly) and c(CPC-Ala) in the prevention of tardive dyskinesia is proposed.

Induction of dopaminergic supersensitivity after a single dose of the neuroleptic isofloxythepin.

The development of dopaminergic supersensitivity was evaluated, after single oral administration of the long-acting neuroleptic drug isofloxythepin, in nigrostriatal and tuberoinfundibular system in the rat. Isofloxythepin (5 mg/kg orally) increased concentration homovanillic acid (HVA) in the striatum for up to 24 h after administration, whereas a significant decrease below control values was found after 4-5 days. A similar biphasic effect appeared in behavior, since there was an enhancement of apomorphine stereotypy 4-5 days after administration of isofloxythepin (5 and 10 mg/kg orally). Both findings agree with the hypothesis of development of nigrostriatal dopaminergic supersensitivity at long intervals after isofloxythepin. On the other hand, the increase in prolactin (PRL) secretion induced by isofloxythepin indicated only the blocking action of this drug on dopamine receptors in the tuberoinfundibular system, and provided no evidence for tuberoinfundibular dopaminergic supersensitivity after neuroleptic treatment. It is concluded that a single dose of isofloxythepin is capable of inducing dopaminergic supersensitivity in the nigrostriatal system, but not in the tuberoinfundibular system.

Pharmacological properties of a potent neuroleptic drug octoclothepin.

Octoclothepin, 8-chloro-1-(4-methylpiperazino)-10,11-dihydrodibenzo (b,f) thiepin, is a very potent neuroleptic drug with pronounced central antidopaminergic and antiserotonin actions. In most animal experiments, its plharmacological profile resembles that of perphenazine. Octoclothepin reveals an intensive central depressant action in a series of observational and instrumental procedures in rodents. Its active oral doses are within the range of 0.54 to 2.2 mg kg-1 in mice and of 0.1 to 4.8 mg kg-1 in rats. Octoclothepin possesses high cataleptogenic and anti-apomorphine activities in rats; it is able to exert full protection against apomorphine-induced emesis in dogs after the dose of 0.1 mg kg-1 s.c. Octoclothepin reduces some actions and toxicity of d,l-amphetamine and phenmetrazine in rodents. In the rat corpus striatum, octoclothepin in doses of 0.5 and d1.5 mg kg-1 s.c. reduces the DA level and raises the HVA and DOPAC levels significantly. Octoclothepin has antihistamine, antiserotonin and antianaphylactoid actions, it exhibits a high protection against the lethal action of adrenaline and noradrenaline in mice and rats, respectively. Acute toxicological data in mice, rats, rabbits and dogs are given. Clinical antipsychotic effectiveness of octoclothepin has been verified in a large population of psychiatric patients.