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Biomedical subjects

J R Leite

Publications and source records attributed to J R Leite.

32 records · Page 2Linked to original sources
PubMed1986

Pharmacology of lemongrass (Cymbopogon citratus Stapf). III. Assessment of eventual toxic, hypnotic and anxiolytic effects on humans.

A herbal tea (called an abafado in Brazil) prepared from the dried leaves of lemongrass was administered to healthy volunteers. Following a single dose or 2 weeks of daily oral administration, the abafado produced no changes in serum glucose, urea, creatinine, cholesterol, triglycerides, lipids, total bilirubin, indirect bilirubin, GOT, GPT, alkaline phosphatase, total protein, albumin, LDH and CPK. Urine analysis (proteins, glucose, ketones, bilirubins, occult blood and urobilinogen) as well as EEG and EKG showed no abnormalities. There were slight elevations of direct bilirubin and of amylase in some of the volunteers, but without any clinical manifestation. These results taken together indicate that lemongrass as used in Brazilian folk medicine is not toxic for humans. The eventual hypnotic effect of lemongrass was investigated in 50 volunteers who ingested samples of lemongrass and a placebo under double-blind conditions. The parameters (i.e. sleep induction, sleep quality, dream recall and rewakening) did not show any effect of lemongrass as compared to the placebo. Eighteen subjects with high scores of trait-anxiety were submitted to an anxiety-inducing test following taking lemongrass or placebo under double-blind conditions. Their anxiety levels were similar, indicating that the abafado of the plant does not have anxiolytic properties. It is concluded that lemongrass, one of the most popular Brazilian herbal medicines, used for its alleged CNS-depressant effects, is atoxic but lacks hypnotic or anxiolytic properties.

Administration, Oral↗
PubMed1983

Aminooxyacetic acid induced accumulation of GABA in the rat brain. Interaction with GABA receptors and distribution in compartments.

The effect of aminooxyacetic acid (AOAA, 90 mg/kg i.v.) on bicuculline, picrotoxin and 3-mercaptopropionic acid (3-MPA) induced convulsions and on GABA concentrations in cerebellum, whole brain and a synaptosomal fraction of whole brain was investigated. At various intervals after AOAA the rats were either injected with one of the convulsive drugs or sacrificed for analysis of the GABA concentration. AOAA caused a rapid initial (0-30 min) and a later slower increase of GABA in cerebellum and whole brain. In the synaptosomal fraction the GABA accumulation was delayed and less pronounced when compared to the whole brain. The bicuculline induced convulsions were markedly potentiated during the first hour but completely blocked from 2-6 h after AOAA. Picrotoxin showed a somewhat different pattern to bicuculline in the interactions with AOAA. The initial strong potentiation was not observed but the later phase of protection was present. In the interactions with 3-MPA, the effect of AOAA was always protective. The time to onset of convulsions was gradually increased during the first 30 min after AOAA. This protective effect remained practically unchanged up to 6 h after AOAA. However, once started, the convulsions were generally of the same duration and intensity. The results can be interpreted as GABA accumulating after AOAA stimulates GABA receptors to a degree more or less proportional to the whole brain GABA concentration and further that GABA synthetized in neurons is liberated, stimulates inhibitory bicuculline sensitive (predominant) and excitatory bicuculline insensitive receptors and is captured to a large extent by non-neuronal cells.

3-Mercaptopropionic Acid↗
PubMed1982

Effects of cannabidiol on behavioral seizures caused by convulsant drugs or current in mice.

In mice, running, clonic and tonic convulsions and lethality were assessed following transcorneal (electroshock) current or convulsant drugs, each administered alone and after cannabidiol (CBD) pretreatment. CBD prevented tonic convulsions caused by a convulsant current (CC) 99.99, and by the convulsant dose (CD) 99.99 values of gamma-aminobutyric acid (GABA) inhibitors, 3-mercaptoproprionic acid (3MPA), picrotoxin (PIC), isonicotinic acid hydrazine (INH), pentylenetetrazol (PTZ) and bicuculline (BIC). Rankorder potencies, based on the antitonic ED50 of CBD, were: 3MPA greater than PIC = current = PTZ = BIC. Further, CBD prevented 3MPA-induced lethality, but failed to prevent the occurrence of the other behavioral endpoints of the above treatments. CBD also failed to prevent convulsions and lethality caused by the CD 99.99 of strychnine, a glycine antagonist. The differential effects of CBD suggest that the cannabinoid acts to inhibit seizure spread in the CNS by an action on GABA, but not glycine, mechanisms.

Animals↗
PubMed1982

Effects of sodium barbitone on learning and memory-storage of an appetitive and an aversive task.

In order to test the effects of sodium barbitone on the acquisition and retention of an appetitively and an aversively reinforced behavior, mice were trained in a spatial discrimination Y-maze task. Learning was observed in both situations, with acquisition unimpaired by the drug. Sodium barbitone did, however, affect retention of both tasks in all groups treated with the drug before training. Results are discussed in light of the various modes of action of this drug, i.e., as an inhibitor of protein synthesis, as a blocker of catecholamine biosynthesis, with regard to its effects on paradoxical sleep and on gamma-amino-butyric acid (GABA).

Animals↗
PubMed1982

Anticonvulsant effects of the (-) and (+)isomers of cannabidiol and their dimethylheptyl homologs.

The anticonvulsant actions of the (-) and (+)isomers of cannabidiol and dimethylheptyl-cannabidiol were studied with the maximal electroconvulsive shock model in mice. The ratio of the times for hindlimb extension and fore limb flexion was recorded as an anticonvulsant index. All the cannabinoids were anticonvulsant. They also potentiated pentobarbitone sleeping time. The (+)isomer was more active than the (-)isomer. Possible mechanisms of actions on receptors or membranes are discussed.

Animals↗
PubMed1978

Effects of chronic ingestion and withdrawal of sodium barbitone on learning in rats.

Rats were submitted to three different manipulations: chronic ingestion of sodium barbitone, which was added to the drinking water; chronic administration of barbitone and subsequent withdrawal of the drug; and drinking water only. Both groups of experimental animals showed deficient acquisition in both shuttle-box avoidance and passive-avoidance response when compared to the control animals. Nevertheless, no impairment was observed in passive avoidance when the period of withdrawal was 15 days. Neither was impairment observed when the animals were tested in a T-maze or in another appetitive task. These results cannot be explained by differences in weight or fluid consumption.

Animals↗
PubMed1978

Effect of chronic administration and withdrawal of sodium barbitone on protein synthesis of rat brain.

After chronic administration of sodium barbitone to rats, a marked increase incorporation of [14C]-Leucine into isolated nerve endings was observed. Withdrawal of the drug resulted in a decreased incorporation with respect to values obtained with chronic ingesting animals. On the other hand chronic administration of the barbiturate produced a decreased incorporation in mitochondrial and microsomal fractions. These results are discussed in relation to the development of tolerance and abstinence syndrome to this drug.

Animals↗
PubMedDate not supplied

Physiological modifications and increase in state anxiety in volunteers submitted to the Stroop Color-Word Interference Test: A preliminary study.

For the experimental evaluation of new drugs with a potential anxiolytic effect, there are animal models that can accurately predict clinical activity. However, because of ethical factors, there are few experimental models that allow a reliable evaluation of the anxiolytic activity of drugs in studies performed with human beings. From among them, the Simulated Public Speaking and Stroop Color-Word Interference Test are notable although they are limited by the need to use subjective evaluation scales. The present study was aimed at making the determination of anxiolytic activity of drugs in normal volunteers less subjective by evaluating physiological as well as psychological alterations in subjects submitted to the anxiogenic situation of the Stroop Color-Word Interference Test. Twenty-four volunteers were submitted to the recorded version of Stroop Color-Word Interference Test, and psychological parameters (state anxiety) and physiological parameters (arterial pressure, heart rate, temperature, skin conductance, and frontal and forearm electromyograms) were evaluated before, during, and after the test. Significant differences in temperature, skin conductance and state anxiety of the volunteers were observed between the test situations. These results indicated that the Stroop Color-Word Interference Test can induce, beyond psychological alterations, some physiological alterations that could be used to make the evaluation of the anxiolytic activity of drugs more objective.

Adult↗
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

A study of the pharmacological actions of Dioclea grandiflora Martius ex Bentham.

Dioclea grandiflora Mart. ex Bent., known as Mucuna or Mucuna of stone, is a member of the Leguminosae family, popularly used for its possible effects on the Central Nervous System (CNS). Reports mention sedative, tonic, and also antiepileptic properties for this plant. In this paper a screening for CNS action was done with aqueous extracts of the seeds. This study was carried out using some animal models for the study of sedative, hypnotic, anxiolytic, anticonvulsive and neuroleptic activity. The results showed that Dioclea grandiflora Mart. ex Bent. demonstrates the general profile of a CNS depressant drug. However, the extract did not exhibit any of the specific profiles tested. Moreover, the results suggest a possible toxicity stemming from the popular or folk use of this plant.

Analysis of Variance↗