Discovery of a novel soluble form of monoamine oxidase in the rat brain

Novel neuroprotective effects with O-benzyl derivative of pralidoxime in soman-intoxicated rodents

Pharmacological properties of oxime reactivators, not related to its ability to regenerate or reactivate nerve agent-inhibited acetylcholinesterase located at nerve synapses, have been reported to be important in protecting against poisoning by the nerve agent soman. Such non-reactivation effects have thus far been associated only with bispyridinium oximes. This study investigated the possibility of creating similar non-reactivation therapeutic effects in the mono-pyridinium ring oxime, pralidoxime (2-PAM) through attachment of alkyl groups of increasing chain length to the oxime functional group. Of the 4 derivatives investigated, only the O-benzyl derivative displayed strong sedative effects in mice and mitigated the development of motor convulsions following soman challenge (1.8 x LD50, subcutaneous). Anticonvulsant effects of this compound were enhanced by co-administration of a non-anticonvulsant dose of atropine sulfate. Administration of equivalent amount of other O-derivatives of pralidoxime failed to elicit similar anticonvulsant actions. Electroencephalographic (EEG) and histopathological studies using the rat model, intoxicated with a lethal dose (1.6 x LD50, s.c.) of soman, confirmed O-benzyl derivative neuroprotective capabilities when used as a pretreatment drug. Microdialysis studies revealed that its neuroprotective effect is related to its ability to attenuate soman-induced increase in acetylcholine.

Effect of oral feeding of essence of chicken on the level of 5-hydroxyindole acetic acid in the cerebrospinal fluid of the rat

The effect of oral feeding of a commercial preparation of essence of chicken (Brand's Essence of Chicken, BEC) on the level of 5-hydroxyindole acetic acid (5-HIAA) in the cerebrospinal fluid (CSF) of the rat was investigated. BEC, when fed to the rat for a period of 3 days, significantly increased the CSF level of 5-HIAA in seven out of 12 animals studied. As the level of CSF 5-HIAA is taken as an indication of 5-hydroxytryptamine (5-HT) activity in the brain, it is possible that BEC increased brain 5-HT activity. This increase was not due to the ingestion of tryptophan, the primary precursor of 5-HT, because BEC contains undetectable level of tryptophan. The data indicate that by causing an increase in brain 5-HT activity, consumption of BEC may lead to the activation of 5-HT-dependent physiological process like sleep improvement, mood elevation, analgesia, facilitation of motor output and regulation of circadian rhythm. However, such a possibility remains to be further investigated.

Reduction of dihydroxyphenylacetic acid by a novel enzyme in the rat brain

A novel enzyme that converts dihydroxyphenylacetic acid (DOPAC) to dihydroxyphenylethanol (DOPET) was found to be present in the microdialysate of the rat brain. The enzyme, named DOPAC reductase, was inhibited by EDTA and stimulated by divalent cations like Zn2+, Mn2+, Co2+ and Cu2+. Its Km, pH optimum and temperature optimum were found to be 32 +/- 2 microM, 7.5 and 40 degrees, respectively. The equivalent acid metabolite of noradrenaline, 3,4-dihydroxymandelic acid, and the methoxylated acids of both noradrenaline and dopamine, 3-methoxy-4-hydroxymandelic acid and 3-methoxy-4-hydroxyphenylacetic acid, were found not to be substrates of DOPAC reductase. Thus, DOPAC reductase may be an enzyme that is specifically involved in the one-step conversion of DOPAC to DOPET in the central metabolism of dopamine.