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Biomedical subjects

S Braz

Publications and source records attributed to S Braz.

8 recordsLinked to original sources
PubMed1991

Antiulcerogenic effects of two Maytenus species in laboratory animals.

Leaves of Maytenus species are commonly used in Brazil for the treatment of gastric ulcers, dyspepsias and other gastric problems. The present study evaluated the antiulcerogenic potential of a boiling water extract of equal parts of M. aquifolium and M. ilicifolia leaves against ulcer lesions induced by indomethacin and cold-restraint stress in rats. Ranitidine and cimetidine were used as reference drugs. The oral and intraperitoneal administration of the extract had a potent antiulcerogenic effect against both types of ulcers. The extract was shown to cause an increase in volume and pH of gastric juice of the animals with the pH effects comparable to those of cimetidine. The results tend to confirm the popular use of the plant.

Administration, Oral↗
PubMed1989

Behavioural manifestations elicited by apomorphine, influence of the route of administration.

In order to investigate the influence of the route of administration on behavioural effects induced by apomorphine (APO), 6 increasing doses were administered by intraperitoneal and by subcutaneous route to male Wistar rats. Dose-response curves for stereotypy, rearing, sedation, grooming, yawning and penile erection were calculated. The occurrence of stereotypy precluded other behavioural manifestations. APO was more potent when administered subcutaneously, with potency ratios between the routes of 10.4 for stereotypy, 4.6 for sedation, 6.8 for grooming, 11.8 for yawning and 7.5 for penile erection.

Animals↗
PubMed1988

Reversal of the increase in apomorphine-induced stereotypy and aggression in REM sleep deprived rats by dopamine agonist pretreatments.

REM sleep deprivation (REMSD) induces augmented responses to dopaminergic agonists. Prolonged administration of neuroleptics induces a similar state, probably by the production of supersensitivity of dopaminergic receptors. Such a supersensitive state could be induced by REMSD as a result of impairment of dopamine neurotransmission. In order to test this hypothesis, bromocriptine, nomifensine, amphetamine, L-dopa, imipramine and electroconvulsive shock (ECS) were administered to rats during REMSD, and aggressive and stereotyped behaviors were measured. Amphetamine and L-dopa pretreatment attenuated the increases in apomorphine-induced stereotypy and aggression in REMSD rats, but ECS selectively reduced apomorphine-induced aggression. The other drugs tested were ineffective on both behavioral tests. Such a selective action may reflect different effects of ECS on different dopaminergic systems such as those involved with stereotypy and aggression. The results suggest that REMSD induces an increase in dopaminergic sensitivity which may be reversed by pretreatment with some dopaminergic agonists.

Aggression↗
PubMed1987

Does REM sleep deprivation induce subsensitivity of presynaptic dopamine or postsynaptic acetylcholine receptors in the rat brain?

Yawning behavior was used to evaluate the sensitivity of presynaptic dopamine receptors and postsynaptic acetylcholine receptors of normal and REM sleep-deprived (REMSD) rats. The results show a lowering of the dose-response curve obtained with apomorphine and pilocarpine, as well as a shift to the right in the curve obtained with physostigmine. These results suggest that REMSD induces subsensitization of presynaptic dopamine receptors and/or postsynaptic acetylcholine receptors with different characteristics related to the mechanism of action of the cholinomimetic agent employed.

Animals↗
PubMed1986

REM sleep deprivation induces a decrease in norepinephrine-stimulated 3H-cyclic AMP accumulation in slices from rat brain.

Beta adrenergic sites in rat brain are reduced after repeated treatment with antidepressant drugs, with REM sleep deprivation (REMSd) having the same effect. This paper reports the effects of REMSd in the production of 3H-cyclic AMP in frontal cortical slices by NE challenge. Data presented in this paper report a marked decrease in 3H-cyclic AMP synthesis after REMSd, which is in accordance with previous results showing adrenergic receptor down-regulation following REMSd. Results are discussed in view of possible interaction with dopaminergic systems and depression management.

Adenylyl Cyclases↗
PubMedDate not supplied

Effect of carbamazepine on dopamine release and reuptake in rat striatal slices.

Carbamazepine has been shown to enhance dopaminergic agonist behavioral effects, but not to displace [3H]spiroperidol binding. To verify if carbamazepine acts presynaptically on dopaminergic neurons, reuptake and release of [3H]dopamine were measured in rat striatal slices in vitro. It was observed that carbamazepine blocked 20% of the reuptake of [3H]dopamine, while cocaine blocked 82% of the reuptake, compared with control. Carbamazepine released 62% and tyramine released 92% of the accumulated [3H]dopamine, compared with control. It was concluded that carbamazepine acts presynaptically on striatal neurons, mainly through enhancement of dopamine release. This finding can be related to some behavioral effects described for carbamazepine; however, the importance of its effects in epileptic and manic-depressive patients remains to be clarified.

Animals↗
PubMedDate not supplied

Modifications on dopaminergic and cholinergic systems induced by the water tank technique: analysis through yawning behavior.

Animals deprived of REM sleep by the water tank technique show an important decrease in frequency of yawning, induced by dopaminergic (apomorphine in low doses) and cholinergic (physostigmine and pilocarpine) agonists, if they are tested immediately after the 96 hr of deprivation. In order to understand the mechanisms underlying the effects of REM sleep deprivation on dopaminergic and cholinergic systems, we decided to test the animals after a recovery period of 24 hr. It was observed that apomorphine-induced yawning was still significantly reduced, whereas pilocarpine-induced yawning had returned to normal. The findings suggest that REM sleep deprivation alters dopaminergic and cholinergic systems in different ways: it seems that the interference on the dopaminergic system is prior and stronger than on the cholinergic system, thus its recovery demands more time.

Animals↗