The effects of peptide and nonpeptide antagonists of angiotensin II receptors on the noradrenaline uptake of different brain structures in rats with angiotensin II-induced increase of water intake.

Angiotensin II (ANG II) significantly increased noradrenaline (NA) uptake by cortical, hypothalamic and hippocampal synaptosomes thus activating noradrenergic neurotransmission. ANG II did not affect NA uptake by striatal synaptosomes. The interaction between AT1 receptors and noradrenergic neurons and the involvement of brain noradrenergic neurotransmitter system in ANG II-induced drinking in rats is suggested by the increase of NA uptake in hypothalamus and frontal cortex which are rich in AT1 receptors and are of importance for drinking behavior. The ANG II-receptor antagonists losartan, EXP 3174, sarmesin and saralasin decreased NA uptake in all brain regions studied as compared to the uptake in the same brain regions of ANG II-injected animals thus antagonising the effect of ANG II. There is no relationship between the inhibition of ANG II-induced water intake and the changes of NA uptake under the effect of the ANG II-receptor antagonists.

The effects of peptide and nonpeptide antagonists of angiotensin II receptors on the level of brain biogenic monoamines in rats with angiotensin II-induced increase of water intake.

The effects of peptide and nonpeptide angiotensin II (Ang II)-receptor antagonists (losartan, EXP-3174, saralasin and sarmesin) on the levels of the biogenic monoamines dopamine, noradrenaline and serotonin in the frontal cortex, striatum, hypothalamus and hippocampus of rats with Ang II-induced water intake were investigated. Ang II administered i.c.v. at a dose inducing drinking behavior in rats significantly changed the levels of biogenic monoamines. The latter were also significantly affected by the Ang II-receptor antagonists, as in most cases the drugs antagonized the effect of Ang II. Most pronounced were the effects of Ang II and Ang II-receptor antagonists on the dopamine levels. These levels were reduced to zero after Ang II in all brain structures studied. The drugs tested increased the dopamine levels, restoring their values to the values in vehicle-injected rats. Ang II-receptor antagonists exerted mosaic effects on noradrenaline and 5-HT (serotonin) levels depending on both--the type of biogenic monoamine and the brain structure. There was no relationship between the inhibition of Ang II-induced water intake and the changes in the levels of brain biogenic monoamines under the effect of the Ang II-receptor antagonists. These antagonists may play a role in the modulation of brain monoaminergic neurotransmitter systems.

The effects of peptide and nonpeptide angiotensin II-receptor ligands on the activity of brain monoamine oxidase in water-repleted rats.

The effects of i.c.v. administered peptide and nonpeptide ANG II-receptor ligands (losartan, EXP 3174, saralasin and sarmesin) on monoamine oxidase A (MAO-A) and MAO-B activities in the frontal cortex, striatum, hypothalamus and hippocampus of water-repleted rats were investigated. Alterations in MAO-A and MAO-B activities were found in different rat brain regions after ANG II which depended on the isoenzyme type and brain structure. MAO-A activity significantly increased in the frontal cortex and hypothalamus, brain regions containing AT1 receptors, mainly. MAO-A and MAO-B activities were affected differently by all studied ANG II-receptor ligands, which in most cases antagonized the effect of ANG II (losartan, an AT1-nonpeptide receptor antagonist being the most effective). There was no clearcut relationship between the inhibition of ANG II-induced water intake and the changes of MAO-A and MAO-B activities under the effect of the ANG II-receptor antagonists studied.

Effects of peptide and non-peptide antagonists of angiotensin II receptors on drinking behavior in rats.

The effects of the non-peptide selective angiotensin II AT1 receptor antagonist DuP 753 and its metabolite EXP 3174, of the peptide ANGII analogues saralasin and sarmesin and of the newly synthesized imidazole compound (1-methyl-4,5-diphenylimidazole) on ANGII-induced drinking in rats were investigated. The effect of the AT2 selective antagonist PD 123319 on ANGII-induced drinking in rats was also studied. DuP 753, EXP 3174, saralasin and sarmesin (peptides and non-peptides) dose-dependently inhibited ANGII-induced water intake. The ID50 values of these drugs showed the following order of potency: EXP 3174 > saralasin > sarmesin > DuP 753 indicating their ability to block central AT1 receptors. The imidazole compound increased ANGII-induced water intake suggesting its AT1 receptor agonistic properties. PD 123319 inhibited ANGII-induced water intake at a higher dose (64 nmol), allowing to assume AT1 receptor agonistic properties.

Hereditary motor and sensory neuropathy--Lom, a novel demyelinating neuropathy associated with deafness in gypsies. Clinical, electrophysiological and nerve biopsy findings.

A previously unrecognized neuropathy was identified in Bulgarian gypsies, and was designated hereditary motor and sensory neuropathy-Lom (HMSNL) after the town where the initial cases were found. It was subsequently identified in other gypsy communities. The disorder, which is of autosomal recessive inheritance, was mapped to chromosome 8q24. It begins consistently in the first decade of life with gait disorder followed by upper limb weakness in the second decade and, in most subjects, by deafness which is most often first noticed in the third decade. Sensory loss affecting all modalities is present, both this and the motor involvement predominating distally in the limbs. Skeletal deformity, particularly foot deformity, is frequent. Severely reduced motor nerve conduction velocity indicates a demyelinating basis, which was confirmed by nerve biopsy. The three younger patients biopsied showed a hypertrophic 'onion bulb' neuropathy. The hypertrophic changes were not evident in the oldest individual biopsied and it is likely that they had regressed secondarily to axon loss. In the eight cases in which brainstem auditory evoked potentials could be recorded, the results suggested demyelination in the eighth cranial nerve and also abnormal conduction in the central auditory pathways in the brainstem. As no myelin genes are known to be located at chromosome 8q24, the disorder may involve a gene for a novel myelin protein or be due to an abnormality of axon-Schwann cell signalling.

Effects of angiotensin II on biogenic monoamine uptake in the brain of nonhypoxic and hypoxic mice.

The effects of angiotensin II (ATII) administered intacerebroventricularly (i.c.v.) at a dose of 0.5 microgram per mouse on dopamine (DA), noradrenaline (NA) and 5-hydroxytryptamine (5-HT) high-affinity uptake in mouse forebrain during hypoxia (asphyxic and hemic) were studied. The influence of hypoxia on biogenic monoamine uptake was also investigated. It was found that DA uptake increased, NA uptake decreased and 5-HT uptake was unchanged after asphyxic hypoxia. Hemic hypoxia had no effect on biogenic monoamine uptake. ATII did not affect uptake of biogenic monoamines in normoxic mice after asphyxic and hemic hypoxia. The results suggest that ATII increases the susceptibility of animals to hypoxia through alterations in the brain high-affinity monoamine uptake.

Effects of beta-adrenoceptor blocker pindolol, calcium antagonist verapamil and their combination on retention in step-down- and shuttle-box-trained rats and on brain biogenic monoamines.

The effects of the beta-adrenoceptor blocker pindolol and the calcium antagonist verapamil administered alone or in combination on retention in step-down- and shuttle-box-trained rats and on the biogenic monoamine levels in the frontal cortex and hippocampus were examined. The chronic oral treatment with pindolol impaired retention in step-down- and shuttle-box-trained rats, decreasing the dopamine (DA) and noradrenaline (NA) levels and increasing the serotonin (5-HT) levels in the cortex and hippocampus. Verapamil did not influence retention in step-down- and shuttle-box avoidance situation and the biogenic monoamine levels in the frontal cortex and hippocampus. It should, however, be noted that the chronic oral treatment with verapamil completely abolished the retention-impairing effect of pindolol, restoring to normal DA, NA and 5-HT levels. These findings might be of interest to clinical practice and suggest the necessity for using a combination of beta-blockers with Ca2+ antagonists in case of prolonged treatment of cardiovascular diseases.

Gene mapping in Gypsies identifies a novel demyelinating neuropathy on chromosome 8q24.

Founder effect and linkage disequilibrium have been successfully exploited to map single gene disorders, and the study of isolated populations is emerging as a major approach to the investigation of genetically complex diseases. In the search for genetic isolates ranging from Pacific islands to Middle East deserts, the 10 million Gypsies resident in Europe have largely escaped the attention of geneticists. Because of their geographical ubiquity, lack of written history and the presumed social and cultural nature of their isolation, Gypsies are construed as not meeting the criteria for a well defined founder population. Gypsy society has a complex structure with subdivisions and stratifications that are incomprehensible to the surrounding populations. Marginalization by the health care systems in most countries results in a lack of information on causes of morbidity and mortality and little is known about hereditary disorders or the population genetic characteristics of Gypsies. This study is the first example of mapping a disease gene in endogamous Gypsy groups. Using lod score analysis and linkage disequilibrium, we have located a novel demyelinating neuropathy to a narrow interval on chromosome 8q24. We show that the disease, occurring in Gypsy groups of different identity and history of migrations, is caused by a single mutation whose origin predates the divergence of these groups.

Effects of angiotensin II on brain monoamine oxidase activity in non-hypoxic and hypoxic mice.

The effects of angiotensin II (ATII) administered intracerebroventricularly (i.c.v.) at a dose of 0.5 microgram per mouse on the activity of monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B) in the forebrain of normoxic and hypoxic mice were studied. The influence of hypoxia (asphyctic and haemic) on MAO-A and MAO-B activity was also investigated. MAO-A activity was increased in haemic hypoxia; MAO-B activity increased in both asphyctic and haemic hypoxia. ATII increased MAO-A activity without affecting MAO-B activity under normoxic conditions. ATII increased MAO-A activity but decreased MAO-B in hypoxic (asphyctic) mice as compared to normoxic controls. The results suggest the role of MAO-A and MAO-B in the ATII-induced increase of susceptibility to acute hypoxia.

Effects of angiotensin II on brain monoamines in nonhypoxic and hypoxic mice.

The effects of angiotensin II (ATII) administered intracerebroventricularly (ICV, acute) and subcutaneously (SC, acute and chronic) on acute hypoxia (asphyctic and hemic), and on the forebrain concentrations of monoamines dopamine (DA), norepinephrine (NE), and serotonin (5-HT) in male mice were studied. ATII in both routes of administration exerted a decrease of the latency to hypoxia-induced convulsions. ATII slightly reduced the brain levels of DA and NE, and did not change those of 5-HT in hypoxic mice. ATII significantly reduced DA and 5-HT concentrations in nonhypoxic (normoxic) mice. Taken together, the results suggest that ATII-induced increase of susceptibility to hypoxia is accompanied by slight alterations in the brain monoamine metabolism.

In vitro and in vivo effect of the nootropic agent adafenoxate on the 5-HT1 sites in different rat brain structures.

1. The effect of the nootropic agent adafenoxate (a structural analogue of meclofenoxate) on the binding parameters of 5-HT1 receptors in vitro and in vivo in rat cerebral cortex, striatum, hippocampus and hypothalamus was studied. 2. The chronic (100 mg/kg per os for 7 days) adafenoxate treatment produced a significant (24.6%) decrease in the density of 5-HT1 sites in the hippocampus. 3. In vitro adafenoxate inhibited specific [3H]5-HT binding with equal potency in all the regions studied with IC50s in the microM range. 4. It is suggested that the decrease in the density of the 5-HT1 sites in rat hippocampus might contribute to the nootropic action of adafenoxate.

Biogenic monoamine uptake by rat brain synaptosomes during aging. Effects of nootropic drugs.

1. In experiments on young (3-5-month-old), adult (10-11-month-old) and old (21-22-month-old) rats, it was found that significant age-related changes occurred in the high-affinity uptake of dopamine (DA), noradrenaline (NA) and serotonin (5-HT) by cortical and striatal synaptosomes. 2. Changes in DA, NA and 5-HT uptake during aging are suggested to be neurochemical correlates of cognition and memory deficits that develops in senescence. 3. The in vitro effects of the nootropic drugs piracetam, aniracetam, meclofenoxate and adafenoxate on the DA, NA and 5-HT uptake by cortical and striatal synaptosomes from young rats were studied. Administered in increasing concentrations (1 x 10(-4) to 5 x 10(-3) M) these drugs inhibited monoamine uptake. 4. Adafenoxate proved to be a more potent monoamine uptake inhibitor than the other three drugs; it inhibited the uptake in the frontal cortex and striatum without selectivity for either monoaminergic system. It is suggested that adafenoxate affects cognition through the involvement of central neurotransmission and particularly through the inhibition of monoamine uptake systems.

Ginsenoside Rg1 inhibits the brain cAMP phosphodiesterase activity in young and aged rats.

1. The in vitro effect of ginsenoside Rg1 from Panax ginseng on the low- and high-KM cyclic AMP phosphodiesterase (cAMP PDE) activity in the frontal cortex, striatum, hypothalamus and hippocampus of young (4-5-month old) and aged (22-month old) rats has been studied. 2. Administered in increasing concentrations (from 5 x 10(-5) M up to 5 x 10(-4) M), ginsenoside Rg1 exerted a pronounced inhibitory effect on the low- and high-KM enzyme activity in all brain structures studied in rats of both age groups. 3. Ginsenoside Rg1 exhibited inhibitory potency similar to that of theophylline. 4. The present results provide evidence for the CNS effects of ginsenoside Rg1 through inhibition of the intracellular level of cAMP.

Adafenoxate abolishes the amnesia induced by neonatal 6-hydroxydopamine treatment in rats.

The effect of neonatal 6-hydroxydopamine (6-OHDA) treatment on learning and memory and on the levels of biogenic monoamines in some brain structures, as well as the influence of the nootropic drug adafenoxate on 6-OHDA effect was studied in shuttle box and step down trained rats. In mature rats injected with 6-OHDA postnatal, learning and retention were impaired and the noradrenaline (NA) level in the frontal cortex and hippocampus was decreased. Adafenoxate abolished the amnestic effect of 6-OHDA and restored the NA level to normal in the above-mentioned brain structures. This finding suggests the important role of the noradrenergic neurotransmitter system in 6-OHDA-induced amnesia and the favorable effect of adafenoxate on learning and memory impaired by 6-OHDA.

Impairment of learning and memory in shuttle box-trained rats neonatally injected with 6-hydroxydopamine. Effects of nootropic drugs.

The effect of neonatal 6-hydroxydopamine (6-OHDA) treatment on learning and retention and on the level of biogenic monoamines in some brain structures as well as the influence of the nootropic drugs--piracetam, aniracetam, meclofenoxate and fipexide on the 6-OHDA-induced effect was studied. Two- way active avoidance (shuttle box) was used. The levels of noradrenaline (NA), dopamine (DA) and serotonin (5-HT) in the frontal cortex, striatum, hypothalamus, hippocampus and pons were measured. In mature rats, injected with 6-OHDA (100 mg/kg s.c.) in the first 3 postnatal days learning and retention were impaired and the NA level in the frontal cortex and hippocampus was decreased. Piracetam (600 mg/kg), aniracetam (50 mg/kg), meclofenoxate (100 mg/kg) and fipexide (10 mg/kg) administered orally 5 days before and 5 days during training, abolished the amnestic effect of 6-OHDA and restored to control values the NA level in the frontal cortex and hippocampus. This finding suggests the important role of the noradrenergic neurotransmitter system in the 6-OHDA-induced amnesia, as well as in the favorable effect of the nootropic drugs tested on 6-OHDA-impaired memory processes.

Behavioral effects of stem-leaves extract from panax ginseng C.A. Meyer.

The behavioral effects of extracts from ginseng stem and leaves (GL), standardized with respect to the total saponines, and from ginseng roots (G115), standardized with respect to the content of ginsenosides were examined in experiments on rats with undisturbed memory and in rats with experimentally-impaired memory (electroconvulsive shock) using the methods for active avoidance (shuttle-box) and passive avoidance (step-down, step-through), the water-maze method and the method for studying exploratory behavior. On multiple administration G115 exerted favorable effects on learning and memory and on the higher nervous activity as a whole. These effects greatly varied with the dose and administration schedules, with the rat strain, with the rat's ability to perform adequately in any particular learning task, and with the behavioral method. The extract from the overground part of ginseng (GL) had, in the majority of cases, an effect weaker than that of G115 or was without effect at all. Based on previous and present results, we discuss the role of the changes in brain biogenic monoamines induced by the extracts for their mechanism of action.

Age-related changes of the effects of a group of nootropic drugs on the content of rat brain biogenic monoamines.

1. The changes in the levels of brain biogenic monoamines (BMAs) after chronic (7 days) treatment with piracetam, aniracetam and structural analogues of aniracetam (p-H, p-F, p-Cl, p-P and m-D) were studied in young and old rats. 2. An age-related significant decrease in the BMA content was established in old rats. 3. Most of the investigated compounds increased the level of one or other BMA in one or other of the brain structures studied. This elevation was predominantly established in old rats. 4. The present results and those from previous behaviour studies show that elevation of one or more of the BMA levels in one or more brain regions plays a beneficial role in the realization of their effects on the processes of learning and memory.

Memory effects of a group of newly-synthesized pyrrolidine derivatives with putative nootropic effect.

The original pyrrolidine derivatives with putative nootropic effect: para-chloro-phenoxyacetyl-2-pyrrolidinone (Mf-P), 1-adamantanyl-2-pyrrolidinone (A-P), 2-oxo-1-pyrrolidine-3,7-dimethylxanthine (A-T) and para-benzoyl-1,4-dipyrrolidinone (p-P), were studied. Toxicological screening performed on mice demonstrated the low toxicity of the compounds. Five- or seven-day oral administration of the substances to rats in a dose of 100 mg/kg weight facilitated the learning process and improved the memory of the rats with most of the conditioned-reflex methods used. Application of Mf-P to 2- and 24-month-old rats for 8 days induced changes in the levels of some biogenic monoamines in the brain structures studied. The results obtained, as well as the results of other studies in this laboratory, show that the pyrrolidine derivatives studied, which can be considered to be original new aniracetam analogues, improve the memory process. This effect varies strongly depending on the regime of application of the compounds studied, on the memory capacity of the experimental animals and on the experimental method used. The changes in the brain neurotransmission induced by the substances studied play an essential role in their mechanism of action.

Age-related changes of cyclic AMP phosphodiesterase activity in rat brain regions and a new phosphodiesterase inhibitor--nootropic agent adafenoxate.

1. The low- and high-KM cyclic AMP phosphodiesterase (cAMP PDE) activity in cerebral cortex, striatum, hypothalamus and hippocampus of young (4-5-month-old) and aged (22-month-old) rats has been studied. 2. A significant rise in the high-KM cAMP PDE activity in the cerebral cortex, hypothalamus and hippocampus in aged rats has been found. 3. The activity of the low-KM cAMP PDE does not change during senescence in all the brain structures studied. 4. In a series of increased concentrations (from 5 x 10(-4) to 1 x 10(-5) M) adafenoxate inhibits low- and high-KM cAMP PDE in most of the brain structures studied in both age groups. 5. The present results provide evidence for realization of the CNS effects of adafenoxate through inhibition of cAMP PDE activity and regulation of the intracellular level of cAMP.

Effect of angiotensin II on the Vogel conflict paradigm and on the content of dopamine and noradrenaline in rat brain.

Experiments on male rats were conducted to test the effect of the octapeptide angiotensin II (AT II), introduced intracerebroventricularly (i.c.v.), on a conflict paradigm (drink-foot shock conflict procedure) and on the levels of dopamine and noradrenaline in the hypothalamus and hippocampus during that test. AT II was found to cause substantial reduction of the number of punished responses (biphasically and dose-dependently: the lower dose (0.1 microgram) and the high dose (5 micrograms) have a stronger effect than the moderate doses), which implies a proconflict or anxiomimetic effect. At the same time AT II (1 microgram) caused a substantial reduction of the dopamine level in the hypothalamus and hippocampus. The explanation of the AT II-induced changes in the conflict behaviour (anxiogenic action) is sought in its interaction with the AT II receptors (binding sites) in the brain structures (hypothalamus, hippocampus, etc.), participating in that behaviour, as well as in its modulating effect on the DA-ergic transmission in these structures.