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Biomedical subjects

V Petkov

Publications and source records attributed to V Petkov.

At least 37 records · Page 2Linked to original sources
PubMed1990

[The effects on the learning process of 4 pyrrolidine derivatives and of cyticholine (experiments on rats in a water maze)].

The experiments were carried out on 104 male white rats and the effects of pyracetamat, aniracetamat and 2 newly synthesized pirolidine derivatives P-CL, P-p as well as of cytidin-diphosphat choline (cyticholine) were examined on training in a water maze. All investigated substances were administered immediately after morning training orally in a dose of 100 mg/kg for a period of 5 days. Ten trainings were undertaken each day twice. Two parameters were determined: time of stay of the rat in the water maze (in seconds) and the number of mistakes (entrance of blind canals). Pyracetamat and cyticholine improved training of rats while the other examined substances showed insignificant effect. A conclusion is made that chemically close nootropic drugs could be differentiated substantially in respect to spatial memory as well.

Animals↗
PubMed1988

Comparative studies on the effects of the nootropic drug adafenoxate and of the cerebral vasodilator flunarizine on arterial smooth muscles.

The effects of the nootropic drug adafenoxate and of the cerebral vasodilator flunarizine were studied on smooth-muscle preparations isolated from rabbits (perfused central ear artery and segments of the thoracic aorta). Both drugs tested did not change the smooth muscle tone. When applied extralumenally adafenoxate decreased the noradrenaline (NA)-evoked arterial contractions. Adafenoxate (especially in high concentrations) markedly relaxed the NA-contracted arterial preparations. The arterial contractions in response to low-frequency electrical stimulation (ES) were moderately potentiated by high concentrations of extralumenal adafenoxate, but were decreased by intralumenal administration of the drug. Administered prior to or after NA adafenoxate antagonized its contractile effects on the aortic segments (this effect was much pronounced when the smooth-muscle preparations were contracted by NA). Flunarizine exerted similar but less pronounced inhibitory effects on the NA- or ES-evoked contractions of the smooth-muscle preparations. The only essential difference between the two drugs tested was that extralumenal flunarizine inhibited the arterial contractions in response to ES. It is suggested that if adafenoxate exerts an antivasoconstrictory effect not only on the peripheral arteries but also on the cerebral blood vessels, this effect might play an important role for the realization of the nootropic action of this compound.

Animals↗
PubMed1987

On the mechanism of the smooth-muscle action of rosanol.

In vivo and in vitro experiments were performed to clarify some aspects of the mechanism of the smooth-muscle action of rosanol prepared from rose oil. On dogs (in vivo) and on isolated segments from guinea-pig ileum (in vitro) rosanol at high doses exerted a slight inhibitory effect on the activated gastrointestinal motility. The cholinolytic rosanol action proved in in vitro experiments, was found to play an essential role in the mechanism of its gastrointestinal motility-inhibiting effect. The present studies showed a pronounced antagonistic effect of rosanol on the KCl-increased Ca2+ level in rabbit aorta. It might be suggested that this effect of rosanol is also involved in the inhibitory action of rosanol on the activated gastrointestinal motility.

Animals↗
PubMed1986

Bulgarian traditional medicine: a source of ideas for phytopharmacological investigations.

Some data about the use of medicinal plants in Bulgarian traditional medicine in the Middle Ages and in modern times are presented and the results of 40-year-long experimental-pharmacological investigations on many medicinal plants used in Bulgarian traditional medicine are reviewed. In-depth discussion is presented on the investigations of garlic (Allium sativum L.), a plant widely used by Bulgarian people for treating different diseases. Data from studies on a large number of plants used for treatment of hypertension, infectious diseases and as diuretic and spasmolytic remedies are summarized.

Bacterial Infections↗
PubMed1984

GABAergic influence on the effects of elymoclavine on exploratory behaviour of rats in open field.

The GABAergic influence on the effects of the ergot alkaloid elymoclavine on exploratory behaviour of rats in open field was studied using pharmacological tools. GABA was found to reduce the elymoclavine-stimulated exploratory behaviour. The GABAergic antagonists picrotoxin and bicuculline reversed the influence of GABA on the elymoclavine effects. The indirect GABA mimetics nipecotic acid, aminooxyacetic acid, di-n-propylacetate and semicarbazide also reduced the behavioural effects of elymoclavine. The data suggest some role of different functional states of the GABA system and of the close relationship between GABA and DA in the brain in the effects of elymoclavine on exploratory behaviour.

Aminooxyacetic Acid↗
PubMed1984

Participation of serotoninergic, GABA-ergic and opiate mechanisms in the genesis of amphetamine stereotypy.

In experiments on rats it has been observed that the intensity of amphetamine-induced (6 mg/kg s.c.) stereotypy is reduced by the blockers of the serotonin (5-HT), GABA- and opiate receptors, respectively danitracene (3 mg/kg i.p.), picrotoxin (2 mg/kg i.p.) and naloxone (10 mg/kg s.c.). Applied 24 hours after the serotonin depletor para-chlorophenylalanine (PCPA--300 mg/kg i.p.), amphetamine induced more pronounced but earlier disappearing stereotypy. Also more intensive but longer was the stereotypy induced by apomorphine (2.5 mg/kg i.p.) applied after PCPA. The stimulator of the serotonin receptors quipazine (10 mg/kg i.p.) potentiated amphetamine stereotypy and eliminated haloperidol catalepsy (1 mg/kg i.p.). The blocker of the cholinergic receptors atropine (30 mg/kg i.p.) increased and prolonged amphetamine stereotypy. In the interpretation of the results obtained an attempt is made to substantiate the thesis that dopamine (DA) released under the effect of amphetamine by the nigrostriatal terminals, acts at least partially not as inhibitory, as it is usually accepted, but as excitatory transmitter. It is considered that the results obtained show that DA released from the nigrostriatal pathway exercises its typical inhibitory influence on the striatum, by stimulating 5-HT, GABA and opiate neurons situated in nucleus caudatus. The ostensibly contradictory results from the experiments with PCPA to the proposed hypothesis are explained with the development of sensitization of the 5-HT receptors.

Amphetamine↗
PubMed1984

On the pharmacology of the ergot alkaloid elymoclavine.

Pharmacological investigations of the ergot alkaloid of the group of clavines, elymoclavine, isolated from Claviceps sp. cp. II showed the following results: The LD50 for mice for 24 h was 350 (228-535) mg/kg and for rats 145 (81-258) mg/kg. Elymoclavine induced a dose-dependent stereotypy (doses of 2 to 10 mg/kg) in rats and mice which was antagonized by haloperidol and pimozide. It prevented the development of haloperidol catalepsy in rats and produced rotations contralateral to the striatal lesions with 6-OHDA which were antagonized by pimozide and partly by cyproheptadine. Elymoclavine, like bromocriptine, decreased the plasma level of prolactin. Furthermore, elymoclavine increased the exploratory activity of rats in open field; this effect was antagonized by haloperidol and was essentially influenced by many substances acting on different transmitter systems (NA, DA, GABA). Elymoclavine inhibited the picrotoxin and electroshock convulsive seizures but potentiated the pentylenetetrazol ones in mice as these effects were differently influenced by pimozide, haloperidol, 5-HTP, atropine and phentolamine. 100 and 250 micrograms/kg of elymoclavine produced a considerable and persisting decrease of the blood pressure in anaesthetized cats. At 1 X 10(-6) M, without producing any per se effect, elyoclavine decreased the contractile effects of acetylcholine, nicotine, BaCl2 and PGE1 as well as the field electrical stimulation-induced contractions in an isolated segment from guinea-pig ileum. The observed effects of elymoclavine are mainly due to its dopaminergic agonist action. It seems, however, that influences on other transmitter receptors also underlie the mechanism of action of this ergot alkaloid.

Animals↗
PubMed1984

On some central effects of elymoclavine.

The pharmacological investigation of the ergot alkaloid of the group of clavines elymoclavine isolated from Claviceps sp. cp. II showed the following: LD50 for mice for 24 hours was 350 (228 divided by 535) mg/kg and for rats--145 (81 divided by 258) mg/kg; elymoclavine induced a dose-dependent stereotypy in rats and mice which was antagonized by haloperidol and pimozide; it prevented the development of haloperidol catalepsy in rats and produced rotations contralateral to the striatal lesions with 6-OHDA which were antagonized by pimozide and partly by cyproheptadine. Elymoclavine increased the exploratory activity of rats in open field as this effect was antagonized by haloperidol and was essentially influenced by many substances acting on different transmitter systems (NA, DA, GABA). Elymoclavine inhibited the picroroxin and electroshock convulsive seizures but potentiated the pentylenetetrazol ones in mice as these effects were differently influenced by pimozide, haloperidol, 5-HT, atropine and phentolamine. The observed effects of elymoclavine are mainly due to its DAergic agonistic action. It seems, however, that influences on other transmitter receptors also underlie the mechanism of action of this ergot alkaloid.

Animals↗
PubMed1984

Experimental pharmacological study of three species from genus Salvia.

Fifteen extracts isolated from three species of genus Salvia were studied: two from Salvia officinalis, seven from Salvia triloba and six from Salvia verbenaca. Their effects on the blood pressure of cats and spontaneously hypertensive rats were examined. The smooth-muscle effects of the extracts were studied on isolated segments of guinea-pig ileum. The effects of some of the extracts on hexobarbital anaesthesia were investigated. Applied intravenously and duodenally, aqueous-alcohol extract of Salvia officinalis causes moderate but prolonged lowering of the blood pressure in cats. Decoction of Salvia triloba also possesses a similar effect (in experiments on spontaneously hypertensive rats). Most of the extracts isolated from Salvia officinalis and Salvia triloba inhibit to various degrees smooth-muscle contractions induced by acetylcholine, histamine, serotonin and BaCl2, whereas extracts of Salvia verbenaca usually potentiate them. Substances isolated from Salvia triloba prolong hexobarbital sleep. Future studies of substances isolated from Salvia officinalis and Salvia triloba are promising with a view to their spasmolytic and hypotensive actions. There exist marked interspecies differences in the pharmacological effects of biologically active substances isolated from genus Salvia.

Anesthesia↗
PubMed1983

Neurotransmitted effect of prostaglandin F2 alpha in isolated cat jejunum.

Prostaglandin F2 alpha (PGF2 alpha) (1 nM-0.1 microM) increased the amplitude of the spontaneous phasic contractions and produced tonic contraction of the isolated longitudinal muscle from the cat jejunum. The amplitude of the electrically-induced contractions increased by PGF2 alpha (1 nM-10 nM) in a dose-dependent degree. PGF2 alpha decreased the inhibitory effect of indomethacin (30 microM) on the contractile response to electrical stimulation. Hexamethonium did not influence the PGF2 alpha effect on the electrically-induced contractions but inhibited the PGF2 alpha-produced tonic contractions. The contractile effect of PGF2 alpha depended on the number of impregnated nerve cells and terminals preserved in the preparations long after dissection. The data suggest that PGF2 alpha increases the acetylcholine release and that there is a "stepwise" action of PGF2 alpha on the transmitter release from the postganglionic or preganglionic cholinergic terminals depending on the PGF2 alpha concentration and leading to phasic or tonic smooth-muscle contractions.

Acetylcholine↗
PubMed1983

Effects of the tripeptides TRH, MIF and MAF on the cerebral dopaminergic system.

Some central effects of the tripeptides TRH (thyroliberine), MIF (melanostatine or C-terminal fragment of oxytocine) and MAF (C-terminal fragment of gastrine) have been studied in experiments on mice and rats. Upon intraperitoneal administration in mice, TRH and MIF exercise central stimulating effects: they reverse the reserpine-induced decrease in the rectal temperature, ptosis of the eyelids, hypomotility, decreased content of the cerebral homovanillic acid (HVA); they antagonize haloperidol catalepsy and the increased HVA concentration). The tripeptides potentiate apomorphine stereotypy in rats, when injected in the striatum. The results obtained characterize TRH and MIF as drugs which are capable of activating the cerebral dopaminergic receptors by antagonizing the effects of reserpine and haloperidol, MAF--as a substance acting similar to the dopaminergic receptor blockers. Consequently, the cerebral dopaminergic system is an important unit for the realization of the central effects of these low-molecular peptides.

Animals↗
PubMed1983

On the effects of diazepam, hyoscine and oxotremorine on acetylcholine release from the cerebral cortex.

The amount of acetylcholine (ACh) released in perplex cylinders filled with 0.5 ml eserinized Ringer solution and placed on the exposed rat cerebral cortex was determined every 10 min. For the purpose bioassay on leech dorsal muscle was used. ACh was calculated in pmoles/cm2 min-1. It was found that diazepam decreased by 30 per cent, hyoscine increased by 36 per cent and oxotremorine also decreased by 24.5 per cent the ACh output from the cerebral cortex. Hyoscine counteracted to a considerable extent the diazepam-induced inhibition of ACh output, but oxotremorine did not potentiate the inhibitory effect of diazepam on ACh output, in some cases it even prevented it. It could be assumed that the effects of hyoscine and oxotremorine result to a considerable extent from their action on presynaptic autoinhibitory muscarinic receptors. However, it is also possible for the effects of oxotremorine to be important influences on the cortical cholinergic mechanisms, mediated by adrenergic structures. The results obtained suggest a definite role of the cerebral cholinergic system in the mechanism of action of the benzodiazepine derivative diazepam.

Acetylcholine↗