Microspectrofluorimetric analysis of the formaldehyde induced fluorescence in midbrain raphe neurons.
The formaldehyde induced fluorescence in perikarya localized in the midbrain rephe nuclei was investigated using the Falck-Hillarp technique in combination with qualitative (spectral analysis) and quantitative microspectorfluorimetry. The spectral evidence obtained after various pharmacological and lesion experiments with the neurotoxic compounds 5,6-dihydroxytryptamine and 5,7-dihydroxytryptamine, strongly favours the view that the vast majority of the perikarya in the cell groups B-7, B-8 and B-9 (according to Dahlström and Fuxe) are 5-hydroxytryptamine neurons, defined as structures capable of synthesizing, metabolizing, and storing 5-hydroxytryptamine. The spectral data indicate that the 5-hydroxytryptamine neurons might contain in addition to 5-hydroxytryptamine another indolealkylamine, possibly tryptamine, in low concentrations. The perikarya were shown to be able to take up and accumulate exogenously administered 6-hydroxytryptamine provided that monoamine oxidase was inhibited. Quantitative microfluorimetric analysis disclosed that the tryptophan hydroxylase inhibitor p-chlorophenylalanine was unable to block effectively this enzyme in the 5-hydroxytryptamine perikarya, although acutely a partial blockade was observed. The 5-hydroxytryptamineerogenously to the action of p-chlorophenylalanine and this might be associated with different states of neuronal activity. The difference in potency of p-chlorophenylalanine as regards tryptophan hydroxylase inhibition in perikarya and in nerve terminals may be related to different properties of tryptophan hydroxylase in various parts of the neuron and/or to a high turnover of the enzyme in the perikarya.
D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000187:drug effects; D010134:Fenclonine / Q000494:pharmacology; D005453:Fluorescence; D005557:Formaldehyde / Q000494:pharmacology*; D006651:Histocytochemistry; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism; D008636:Mesencephalon / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011149:Pons / Q000187:drug effects; D051381:Rats; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000378:metabolism; D014365:Tryptophan Hydroxylase / Q000378:metabolism; D014747:Vinblastine / Q000494:pharmacology
D005557:Formaldehyde; D012701:Serotonin; D014747:Vinblastine; D014364:Tryptophan; D006916:5-Hydroxytryptophan; D014365:Tryptophan Hydroxylase; D010134:Fenclonine