Exercise increases endogenous urinary monoamine oxidase benzodiazepine receptor ligand inhibitory activity in normal children

Isatin, an endogenous MAO inhibitor, and a rat model of Parkinson's disease induced by the Japanese encephalitis virus

A single dose of isatin (indole-2,3-dione)(i.p.), an endogenous MAO inhibitor, significantly increased norepinephrine and 5-hydroxytryptamine concentrations in the rat brain and also significantly increased acetylcholine and dopamine (DA) levels in the rat striatum. Urinary isatin concentrations in patients with Parkinson's disease tend to increase according to the severity of disease. We have developed a rat model of Parkinson's disease induced by the Japanese encephalitis virus (JEV). The distribution of the pathological lesions of JEV-rats resemble those found in Parkinson's disease. Significant behavioral improvement was observed in JEV-rats after isatin, L-DOPA and selegiline administration using a pole test. Both isatin and selegiline prevented the decrease in striatum DA levels of JEV-rats. The increased turnover of DA (DOPAC/DA) induced by JEV was significantly inhibited by isatin, but not selegiline. These findings suggest that JEV-infected rats may serve as a model of Parkinson's disease and that exogenously administered isatin and selegiline can improve JEV-induced parkinsonism by increasing DA concentrations in the striatum.

Regional and molecular separation of the four bioactivities of 'tribulin'

The endocoid tribulin has four known bioactivities: monoamine oxidase A and B inhibitory activities (MAO-AI and MAO-BI) and peripheral and central benzodiazepine receptor binding inhibitory activities (PBR-I and CBR-I). Analysis of the four bioactivities in rat tissue reveals regional dissociation. Most notably liver was particularly rich in PBR-I yet contained no detectable MAO-AI. In addition we have succeeded in separating the four activities from human urine. MAO-AI and MAO-BI have greater retention on charcoal than PBR-I and CBR-I when eluted step-wise with aqueous methanol. MAO-AI can be separated from MAO-BI and in addition PBR-I can be separated from CBR-I by step aqueous methanol elution from Amberlite XAD-4. Hence we present two lines of evidence that, contrary to the original view, tribulin is composed of a number of distinct molecular components.

Determination of isatin in urine and plasma by high-performance liquid chromatography

A method for the detection and determination of isatin (indole-2,3-dione) in urine and plasma by high-performance liquid chromatography has been developed. It consists of a two-step purification using two different columns with UV detection. With this method, we have reconfirmed that isatin is present in human urine. We have also demonstrated that isatin is present in human plasma and that the isatin levels in spot urine samples reflect the plasma isatin levels. In the present report we describe a rapid and sensitive means of determining urine and plasma isatin for laboratories equipped with a high-performance liquid chromatography system.

Stressor predictability influences open field behavior, pain sensitivity and brain MAO inhibitory activity (tribulin) in the rat

The effects of predictable or unpredictable shocks on ambulation, pain sensitivity, plasma catecholamines and heart and brain monoamine oxidase (MAO) inhibitory activity were investigated in rats. Animals showed plasma catecholamines and heart MAO inhibitory activity sensitization irrespective of type of treatment, while differences between groups were observed when open field and hot plate tests and brain MAO inhibitory activity were considered. These effects parallel those observed using the classic triadic design leading to the helpless state. Our results suggest that predictability per se is able to generate this phenomenon.

The stress-induced reduction in monoamine oxidase (MAO) A activity is reversed by benzodiazepines: role of peripheral benzodiazepine receptors

1. The effect of benzodiazepine pretreatment on the stress-induced decrease in MAO activity in rat tissues using footshock as stress model was investigated. 2. Animals were injected with vehicle, Lorazepam (1.25 mg/kg), or Clonazepam (0.5 mg/kg) 2 hr before or with PK 11195 (0.45 mg/kg) 2.5 hr before being subjected to one session of 10 inescapable footshocks or to a sham session. At the end of the session animals were sacrificed and MAO A and B activities in hearts and brains were determined. 3. Pretreatment of the animals with both Lorazepam and Clonazepam abolished the decrease induced by footshock in MAO A activity in brain. Pretreatment with Lorazepam but not with Clonazepam abolished the stress-induced decrease in MAO A in the heart. Pretreatment with PK 11195 before Lorazepam reversed its effects in the heart but not in the brain. Neither footshock nor any of the drugs used had any effect on heart and brain MAO B. 4. Our results suggest that in the heart but not in the brain, peripheral benzodiazepine receptors play a role in the regulation of MAO A activity under stress conditions.

Repeated (isolation) stress increases tribulin-like activity in the rat

1. The effect of repeated isolation stress on MAO inhibitory activity (tribulin) in rat tissues as well as on plasma catecholamine levels was investigated. 2. Animals were subjected to a daily period of isolation (9 min) and sacrificed on days 1, 2, 4, and 5. 3. In brain and cerebellum the levels of both inhibitory activities were found to be significantly higher in animals sacrificed on days 1-2 than in either controls or animals sacrificed on days 4-5. 4. In heart and kidney the highest levels of both activities were found in animals sacrificed on days 4-5. 5. Plasma levels of dopamine on day 4 were significantly higher than those in controls or in any of the experimental groups. Plasma levels of epinephrine showed step-by-step increments from day 1 up to day 5, reaching statistical significance only on day 5. Plasma levels of norepinephrine were significantly increased on days 2, 4, and 5. 6. Under the experimental conditions of this study, we have shown a rapid and short-lasting increment of tribulin in the central nervous system. Its disappearance on days 4-5 could be related to adaptation to the novel situation. Changes in the peripheral tissues appeared later, and a similar adaptation was absent during the period of observation. 7. Tribulin would be related to the stressful situation not only as an anxiety-promoting agent but also in contributing to the maintenance of high levels of circulating catecholamines.

Tribulin in post-traumatic stress disorder

Tribulin (endogenous monoamine oxidase inhibitor/benzodiazepine receptor binding inhibitor) output was measured in the urine of 18 patients with post-traumatic stress disorder (PTSD) and 13 controls. The level of the two inhibitory activities was highly significantly correlated in the group as a whole. There was no difference between output of either inhibitor in patients and controls. However, when the PTSD group was subdivided according to various psychometric ratings, a pattern of output did emerge. Levels of both inhibitory activities were higher in agitated compared with non-agitated subjects, and lower in extroverts compared with introverts. This finding supports the view that tribulin output is raised in conditions of greater arousal.

Stress increases endogenous benzodiazepine receptor ligand-monoamine oxidase inhibitory activity (tribulin) in rat tissues

The presence of both MAO and benzodiazepine (BZ) receptor binding inhibitory activities in rat tissues has been reported previously. The two activities were similarly and unevenly distributed in the tissues. This dual inhibitory activity has been termed tribulin. We report here the effect of 1 1/2 hrs cold restraint stress on tribulin activity in rat tissues together with biochemical evidence to support the concept of a physiological role of tribulin. Stress induced a significant increment of both activities in heart and kidney while no significant changes were observed in the other tissues studied. Hearts and kidneys from stressed rats also showed a significant decrease of MAO activity, a significant increase of dopamine content and a significant decrease of the binding of 3H-Ro 5-4864 to peripheral BZ receptors. Scatchard analysis of the saturation curves carried out using 3H-Ro 5-4864 (0.4-10 nM) showed significant Bmax decreases in both organs. No significant change in either of these inhibitory activities was observed in the other tissues studied. These data provide support for a role of tribulin in the biochemical response to stress.

Urinary catecholamine metabolite and tribulin output during lactate infusion

Urinary output of homovanillic acid and 4-hydroxy-3-methoxymandelic acid was decreased both in patients with panic attacks and in normal controls during lactate infusion, whereas that of tribulin (an endogenous monoamine oxidase inhibitor and benzodiazepine receptor binding inhibitor) was increased. There was no change in urinary excretion of any of these compounds during saline infusion. These findings provide further evidence of a link between tribulin output and stress and anxiety in man and point to its possible in vivo action as a monoamine oxidase inhibitor.

Variations in the monoamine oxidase-inhibitory activity ("tribulin?") in pig's urine

Sandler and his colleagues (see Sandler, 1982) have demonstrated the presence of an endogenous inhibitor of the enzyme monoamine oxidase (MAO) and of benzodiazepine receptor binding in the urine and blood plasma of man and rat. The concentrations of this material increased under stress conditions and it has been named "tribulin". In the present experiments MAO-inhibitory activity was found in extracts of urine and plasma samples of domestic pigs. Evidence was obtained that the inhibitory activity was higher when pigs experienced slight discomfort. Thus it appears that pigs produce a substance similar to tribulin. It may become possible to use such MAO-inhibitory activity as an indicator in the assessment of interaction with the environment in pig husbandry.

Distribution of endogenous benzodiazepine receptor ligand-monoamine oxidase inhibitory activity (tribulin) in tissues

The distribution of monoamine oxidase inhibitor-benzodiazepine receptor binding inhibitor, extractable into ethyl acetate at pH 1, was examined in a range of rat tissues. Great variation in the activity of both inhibitors was found in the different tissues, the highest being present in superior cervical ganglion, and lowest in adrenal gland. There was a highly significant correlation between the distribution of the two activities in different tissues, supporting the concept that they both derive from the same molecule (tribulin). The level of inhibitory activity in some of the tissues was such that variations might conceivably play a significant role in vivo.