Methadone N-oxide in the rhesus monkey

Some properties of monoamine oxidase and a semicarbazide sensitive amine oxidase capable of the deamination of 5-hydroxytryptamine from porcine dental pulp

The deamination of 5-hydroxytryptamine, tryptamine and benzylamine by porcine dental pulp membrane preparations is brought about not only by monoamine oxidase, but also by a clorgyline (and deprenyl) resistant), semicarbazide sensitive enzyme. The semicarbazide sensitive enzyme was also inhibited by aminoguanidine, hydroxylamine and phenylhydrazine, but was not affected to any significant extent by incubation at 50 degrees for up to 100 min. There was, on the other hand, considerable inhibition of monoamine oxidase activity after incubation at this temperature. The semicarbazide sensitive enzyme neither metabolised, nor was inhibited by putrescine or cadaverine. Mixed substrate experiments indicated that 5-hydroxytryptamine and tryptamine interacted at the same catalytic centre on the semicarbazide sensitive enzyme.

Effect of lesions of raphe nuclei on the activity of catecholaminergic and serotonergic neurones in various brain regions of the rat in vivo

The dorsal raphe nucleus (DRN), the median raphe nucleus (MRN) and the B9 cell groups were lesioned separately. Then, the concentrations of 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), dopamine (DA), 5-hydroxytryptophan (5-HTP) and dopa were measured in various brain regions. The levels of the two latter compounds presumably reflect the activity of serotonergic and catecholaminergic neurones respectively under the experimental conditions. The findings suggest close functional interrelationships between the two types of neurones. Lesions of cell bodies in the DRN cause decreased activity of catecholaminergic neurones in the striatum, the brainstem, the hippocampus, and the hypothalamus. Lesions of the MRN cause increased activity of catecholaminergic mechanisms in the hypothalamus which may be explained by a functional disinhibition after destruction of the MRN. The other brain regions investigated are not affected. Lesions of the B9 cell group elicit increased activity of catecholaminergic neurones in the brainstem and hippocampus.