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Biomedical subjects

R J Mathew

Publications and source records attributed to R J Mathew.

At least 37 records · Page 2Linked to original sources
PubMed1992

Changes in middle cerebral artery velocity after marijuana.

Velocity of blood flow in the middle cerebral artery was measured with transcranial Doppler flowmeter before, during, and 1 hr after smoking a marijuana cigarette and a placebo cigarette during two separate visits to the laboratory. Ten healthy, right-handed male volunteers with a history of marijuana smoking took part in the study. The participants were drug-free for a minimum of 3 mo before the project. During the experiment, blood pressure, pulse rate, and end tidal levels of carbon dioxide were continually monitored. Marijuana smoking was associated with a significant increase in middle cerebral artery velocity. Although marijuana smoking was associated with increased pulse rate, the changes in blood velocity and pulse rate followed different time courses. Marijuana smoking was not associated with significant changes in blood pressure or end tidal carbon dioxide.

Adult↗
PubMed1992

Changes in cerebral blood velocity after intravenous diazepam.

Cerebral blood velocity (CBV) was measured with transcranial Doppler in 6 normal right-handed male volunteers before and for 50 min after an intravenous injection of 0.1 mg/kg of diazepam and normal saline during 2 separate visits to the laboratory. Blood pressure, pulse rate, end tidal levels of carbon dioxide and mood changes were quantified before and after the injections. Diazepam injection was associated with significant increases in fatigue and sleepiness. There were no significant changes in end tidal carbon dioxide, respiration, pulse rate, and blood pressure after the injection. Postdiazepam CBV was significantly lower following diazepam compared to CBV following placebo.

Adult↗
PubMed1992

Regional cerebral blood flow after marijuana smoking.

Regional CBF was measured with the 133Xe inhalation technique before and thrice after smoking marijuana of two strengths and placebo in 20 physically and mentally healthy male volunteers with a previous history of exposure to marijuana. They were drug-free at the time of the study. Blood pressure, pulse rate, end-tidal carbon dioxide, end-tidal carbon monoxide, and forehead skin perfusion were quantified during the CBF measurements. Blood samples were drawn for quantification of plasma levels of delta 9-tetrahydrocannabinol (THC) before and during the 2 h after smoking marijuana or placebo. Drug-induced intoxication and changes in mood were quantified with rating scales. Marijuana smoking was associated with bilateral CBF increase, which was maximal 30 min later. Greater CBF increases were seen in the frontal region and right hemisphere. No significant CBF changes were seen after placebo. Pulse rate and respiration increased significantly after marijuana but not placebo. Both marijuana and placebo smoking were associated with increased end-tidal carbon monoxide. CBF increase in both hemispheres correlated significantly with degree of intoxication, plasma levels of THC, and pulse rate.

Adult↗
PubMed1992

Middle cerebral artery velocity during upright posture after marijuana smoking.

Marijuana is known to cause symptoms suggestive of orthostatic hypotension such as dizziness and fainting during upright posture. We examined changes in cerebral blood velocity (CBV) and peripheral circulation during upright posture after smoking marijuana in 10 right-handed male subjects with a previous history of exposure to marijuana. The participants were physically and mentally healthy and drug-free for a minimum of 3 months before the experiment. Middle cerebral artery CBV, blood pressure and pulse rate were recorded during reclining position and standing, before and after smoking a high-potency marijuana cigarette or a placebo cigarette administered during 2 separate visits to the laboratory. The participants were questioned about dizziness during the upright position. Six of 10 subjects reported moderate to severe dizziness during standing after marijuana but not placebo. Subjects who experienced severe dizziness during standing showed marked decreases in blood pressure and CBV. Those who reported moderate dizziness showed reduction in CBV but not blood pressure. Subjects who reported mild dizziness after marijuana and after placebo smoking showed minimal changes in blood pressure and CBV. Cerebral ischemia during upright position after marijuana smoking may be caused by hypotension and impaired cerebral autoregulation.

Adult↗
PubMed1991

Evaluation of the effects of diazepam and an experimental anti-anxiety drug on regional cerebral blood flow.

In the normal brain, cerebral blood flow (CBF) and function are closely coupled. Thus, changes in brain function associated with drug-induced anxiety reduction should be accompanied by parallel CBF changes. Benzodiazepines such as diazepam have been reported to reduce CBF. It is unclear, however, if this CBF decrease is specifically a function of the anti-anxiety property of the drug. To examine the relationship between drug-induced anxiety reduction and CBF changes more closely, i.v. injections of an established anxiolytic agent and an experimental anti-anxiety drug were given to patients with generalized anxiety disorder. CBF and anxiety levels were measured before and 30 min after i.v. administration of diazepam (0.12 mg/kg), ondansetron (0.24 mg/kg), and normal saline during separate visits to the laboratory. The order of drug administration was randomized, and the injections were given under double-blind conditions. Diazepam but not ondansetron or saline reduced anxiety. Global CBF reduction was seen after diazepam, but no changes were found following the other two experimental conditions. The CBF values were adjusted for test-retest changes in carbon dioxide levels. Postdiazepam decreases in CBF and anxiety levels did not correlate.

Adult↗
PubMed1991

Substance abuse and cerebral blood flow.

OBJECTIVE AND METHOD: This paper reviews acute and chronic effects of drugs of abuse on cerebral blood flow (CBF) and metabolism and their clinical significance. The most important source of information for the review is human research reports published in refereed journals. A few animal studies, book chapters, and abstracts that are especially relevant are also included. RESULTS: In humans, ethanol in small doses produces cerebral vasodilation; higher doses induce cerebral vasoconstriction. Chronic alcoholism is associated with reduced CBF and cerebral metabolism. Sedatives and antianxiety drugs lead to global reduction in CBF and cerebral metabolism. Caffeine, even in small doses, is a potent cerebral vasoconstrictor. Cerebral vasodilation is seen immediately after cigarette smoking, but chronic smokers show global reduction in CBF. Changes in CBF after marijuana smoking are variable; both increases and decreases are seen. Chronic marijuana smoking, however, seems to reduce CBF. Most inhalants and solvents are vasodilators; chronic abuse is accompanied by a decrease in CBF. A number of drugs of abuse, including ethanol, amphetamines, cocaine, nicotine, and caffeine-phenylpropanolamine combinations, increase the risk for stroke. Reduction in CBF associated with chronic use of ethanol, nicotine, inhalants, and solvents is at least partially reversible upon abstinence. CONCLUSIONS: Topics for future research include regional brain function, which mediates drug-induced mood changes (euphoria); CBF concomitants of psychological and physiological characteristics that increase addiction potential; changes in CBF that accompany withdrawal syndromes; mechanisms responsible for drug-induced stroke; and effects of functional and organic complications on CBF.

Adolescent↗
PubMed1990

Behavioral and cerebrovascular effects of caffeine in patients with anxiety disorders.

Caffeine is believed to induce anxiety in normal people and anxiety disorder patients and panic attacks in panic disorder patients. The drug is also known to reduce cerebral blood flow (CBF). Findings suggesting an anxiety-related cerebral vasoconstrictive factor have been reported. We examined the relationship between changes in anxiety and CBF induced by intravenously injecting 250 mg of caffeine (comparable to 2 cups of coffee) in 8 patients with generalized anxiety disorder, 9 patients with panic disorder and 9 normal controls. CBF measurements were also obtained before and after an injection of normal saline in another group of 9 normal volunteers. The anxiety disorder patients did not show any evidence of increase in anxiety and panic after caffeine. Both patients and controls who received caffeine but not normal controls who received saline showed significant CBF decrease. The CBF changes were unrelated to changes in mood, autonomic activity and carbon dioxide levels.

Adult↗
PubMed1990

Cerebral blood flow responses to inhaled carbon dioxide in schizophrenia.

Carbon dioxide (CO2) is a potent cerebrovasodilator; even mild changes in CO2 are associated with marked changes in cerebral blood flow (CBF). We measured CBF before and after 5% CO2 inhalation in 19 medicated patients with schizophrenia and 16 normal volunteers. Another group of 16 volunteers had 2 CBF measurements under resting conditions. Although both patients and controls showed marked CBF increase during CO2 inhalation, the CBF response was significantly less in the patients. Change in CBF per mm of CO2 was lower in the patients. The second group of controls did not show significant differences between the 2 resting CBF measurements.

Adult↗
PubMed1990

Chronicity and a low anteroposterior gradient of cerebral blood flow in schizophrenia.

Regional cerebral blood flow (CBF) was measured with the 133xenon inhalation technique in 27 patients with schizophrenia of less than 5 years' duration and in 27 patients with schizophrenia of more than 12 years' duration, under resting conditions. Similar measurements were also performed in 54 normal control subjects matched for age and sex. Patients with schizophrenia of long duration had lower anteroposterior gradients of CBF than patients with schizophrenia of short duration and matched control subjects. Covarying out age and end-tidal levels of CO2 did not alter the results.

Adult↗
PubMed1990

Anxiety and cerebral blood flow.

The relationship between anxiety and cerebral blood flow (CBF) is of considerable clinical and research significance. Although a considerable amount of information is available on mechanisms through which anxiety may influence CBF, this topic has not received much attention in psychiatry. Earlier techniques for the measurement of CBF were cumbersome and invasive. With the advent of noninvasive techniques, study of CBF in psychiatric disorders, including anxiety, became easier, and a number of such studies have been conducted. In this article the literature on psychophysiological and clinical aspects of changes in CBF associated with anxiety is reviewed.

Anxiety Disorders↗
PubMed1989

Hyperfrontality of regional cerebral blood flow distribution in normals during resting wakefulness: fact or artifact?

Earlier studies with two-dimensional measurement techniques consistently found higher frontal flow in normal subjects during resting wakefulness. However, this finding could not be confirmed by several laboratories with the more modern and technologically more sophisticated three-dimensional measurement techniques. This discrepancy can have strong implications for psychiatric research in which both types of techniques are frequently used. This article reviews the existing literature, discusses possible reasons for the discrepancy, and evaluates evidence from other sources on the activity of the frontal lobe during wakefulness.

Arousal↗
PubMed1989

Sex roles and regional cerebral blood flow.

Several investigators have reported higher resting cerebral blood flow (CBF) in females as compared to males. The relationship between sex roles as quantified by Bem's Sex Role Inventory and CBF was evaluated in 106 right-handed, physically and mentally healthy, drug-free volunteers. CBF was measured noninvasively with the 133xenon inhalation technique. The CBF values correlated inversely with age and positively with carbon dioxide levels, confirming previous reports. Females obtained significantly higher CBF values than males; the differences tended to be most obvious in frontal regions. Males and females who scored high on femininity showed higher CBF as compared to low-femininity subjects even after the effect of sex was covaried out. High masculine sex role tended to be associated with lower CBF, but the effect was less clear.

Adult↗
PubMed1989

Regional cerebral blood flow changes associated with amyl nitrite inhalation.

Regional cerebral blood flow (CBF), mood states and somatic symptoms were measured before and after inhalation of amyl nitrite in 10 physically healthy volunteers with a prior history of using volatile nitrites for recreational purposes. CBF was measured with the same technique, under identical laboratory conditions, in an equal number of normal volunteers. During CBF measurements, blood pressure, pulse rate, respiratory rate and end-tidal levels of carbon dioxide were monitored. The amyl nitrite group and the control group were compared on CBF, rating scale scores and physiological indices via analysis of variance. Amyl nitrite inhalation was associated with significant global increases in CBF, while the control group did not show any change. Pulse rate increase was the only physiological change associated with administration of the drug. Subjects who received the drug reported significant decrease in anger, fatigue and depression and increased palpitation, breathing difficulty, dizziness and headache. Changes in the rating scale scores, physiological indices, and somatic symptoms after amyl nitrite did not correlate with regional CBF change.

Administration, Inhalation↗
PubMed1989

Acute changes in cerebral blood flow associated with marijuana smoking.

Cerebral blood flow (CBF) was measured in experienced (ES) and inexperienced (IS) marijuana smokers with the 133xenon inhalation technique before and after smoking both a high-potency marijuana cigarette and a placebo marijuana cigarette. CBF was measured twice under resting conditions in a control group. Mood states before and after marijuana smoking were quantified with the Profile of Mood States (POMS). Analyses of POMS factors after smoking marijuana revealed IS had an increase in anxiety while ES had a decrease. IS also had a significant increase in depression and decrease in vigor, but neither variable changed in the ES. After marijuana, CBF decreased in IS, but in ES, it increased in comparison with the 2 control runs. In both IS and ES, CBF changes following placebo administration were similar to those associated with marijuana smoking. However, in IS, the marijuana-induced CBF decrease was significantly higher than that associated with placebo. There were no statistically significant differences between the CBF increase seen after placebo and marijuana in ES. Anxiety, anger, fatigue, confusion and depression had significant negative correlations with CBF while vigor correlated positively, but the anxiety factor was the only one to account for a significant percentage of the change (parital correlation) in hemispheric CBF.

Adult↗
PubMed1989

Changes in cerebral blood flow and mental state after amphetamine challenge in schizophrenic patients.

Changes in regional cerebral blood flow and behavioral and physiological indices were monitored after intravenous administration of d-amphetamine sulfate and placebo in groups of patients with schizophrenia and normal volunteers. Amphetamine administration was associated with decreased anxiety, emotional withdrawal, depressed mood, blunted affect and increased excitement in the patients. Subjects who received amphetamine showed significant increases in systolic and diastolic blood pressure and reduction in end-tidal carbon dioxide. Post-amphetamine cerebral blood flow was decreased equally in both patients and controls. The blood flow change, however, did not show any regional variations.

Adult↗