Date of Award:

5-1-1977

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

Legrande C. Ellis

Committee

LeGrande C. Ellis

Committee

Warren C. Foote

Committee

Kent Van Kampen

Abstract

The radiochemical method for assay of monoamine oxidase developed by McCaman et al. (60) and modified by Urry and coworkers (85) was adapted for use in the rat cerebral cortex. Using this method it was confirmed that monoamine oxidase catabolism of serotonin in the rat brain is significantly inhibited by 10-5 M or greater pargyline and 10-8 M or greater clorgyline. Several pineal, neurohypophyseal, and synthetic substances were evaluated as monoamine oxidase inhibitors in the rat brain using the histochemical technique of Williams et al. (91). These substances included clorgyline, pargyline, arginine vasotocin, arginine vasopressin, Pro-Leu-Gly-NH2 , melatonin, and oxytocin. Monoamine oxidase catabolism of the substrates, tyramine and serotonin, was significantly inhibited by 10-5 M or greater concentrations of pargyline. Types 'A' and 'A' + 'B' enzyme activity for these two substrates showed a ten thousand-fold variation in sensitivity to clorgyline inhibition between animals. In contrast, circumventricular type 'C' monoamine oxidase sensitivity to clorgyline inhibition in the same rats was uniform. This enzyme form was only slightly sensitive to 10-4 M clorgyline when tyramine was the substrate, but it was completely inhibited at 10-4 M clorgyline when serotonin was the substrate. The overall formazan staining from types 'A' and 'B' monoamine oxidase activity varied in intensity between animals and was not proportional to type 'C' activity in the same brains. These data strongly indicate that type 'C' monoamine oxidase activity is controlled independently from types 'A' and 'B' and has different inhibitor sensitivities that are substrate dependent. The type 'C' enzyme form was not detectable in 20 out of 64 rat brains evaluated. Arginine vasotocin, arginine vasopressin, Pro-Leu-Gly-NH2, melatonin, and oxytocin with concentrations ranging from 10-3 M to 10-14 M exhibited no observable monoamine oxidase inhibiting activity when using the substrates, tyramine or serotonin.

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