Localization of thiamine in cholinergic nerve terminals: a histofluorescence study in the electric organ ofTorpedo

Eder, Lorenza; Dunant, Yves

doi:10.1007/bf01260895

Cited by 6 publications

(5 citation statements)

References 11 publications

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“…The results presented in the present, as well as in previous, papers (Eder et al, 1978;Eder and Dunant, 1980) have demonstrated that thiamine, mainly in the form of phosphorylated esters, is present in a very high concentration in cholinergic nerve terminals. The vitamin can be taken up and phosphorylated by the tissue.…”

Section: Resultssupporting

confidence: 85%

“…35, 1287-1296 (1980). Eder et al, 1978) we reported that thiamine (vitamin B,) was present in high concentration in the Torpedo electric organ. The vitamin was found principally in nerve terminals and nerve branches in this tissue; isolated synaptosomes contained a very high amount of thiamine, 55% of it being in the form of triphosphate ester; in addition, the phosphorylation of thiamine exhibited marked changes when the tissue was driven in various functional states.…”

mentioning

confidence: 96%

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Thiamine and Cholinergic Transmission in the Electric Organ of Torpedo

Eder

Dunant²,

Loctin³

1980

Journal of Neurochemistry

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The electrogenic tissue of Torpedo was found to phosphorylate in vitro external [14C]thiamine by a saturable process. The rate of this metabolisaton was increased when acetate, an efficient precursor of acetylcholine (ACh) synthesis in this tissue, was added to the incubation medium, thus increasing the turnover of ACh. Nerve stimulation did not release significant amounts of the previously accumulated [14C]thiamine. Exogenous thiamine modified the size of the electroplaque potential (e.p.p.). At concentrations higher than 10(-3)M the nerve-electroplaque transmission was depressed after a transient increase of the e.p.p. Such a depression was due to a strong decrease of the ACh release. At concentrations equal to or lower than 10(-3)M, thiamine affected transmission in a rather complex fashion. ACh release was decreased or increased depending on concentration, time of application, and mode of stimulation. Oxythiamine, a structural antimetabolite of thiamine, affected the transmission in a very characteristic manner at 10(-5)M and higher concentrations. The amplitude of the e.p.p. was increased and, more strikingly, its duration was prolonged. These changes were not due to an inhibition of cholinesterase activity but to an enhancement of the evoked release of ACh either on single-impulse or repetitive stimulation. Another antimetabolite, pyrithiamine, had no effect on the transmission nor on ACh release. From this and our previous work, it is proposed that thiamine is involved, directly or indirectly, in the process of ACh release. The possible mechanisms of this involvement are discussed.

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Section: Resultssupporting

confidence: 85%

mentioning

confidence: 96%

Thiamine and Cholinergic Transmission in the Electric Organ of Torpedo

Eder

Dunant²,

Loctin³

1980

Journal of Neurochemistry

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“…Histochemical work has suggested that thiamine is mostly localized in nerves and nerve terminals in the electric organ (Eder et al, 1978). This suggestion has been supported by the present study, since thiamine, mainly in the form of TTP, was found in a very high concentration in isolated cholinergic synaptosomes.…”

Section: Presynaptic Localization Of Thiamine In Electric Organsupporting

confidence: 90%

“…On the basis of a histofluorescence investigation, it was suspected that most of the thiamine present in electric organ was associated with nerve trunks and nerve endings (Eder et al, 1978). This was examined biochemically, by comparing the thiamine and ACh content of nerve terminals isolated from this tissue.…”

Section: Thiamine In Isolated Cholinergic Synaptosomesmentioning

confidence: 99%

“…The electric organ of Torpedo marmorata was very suitable for this work, as it is provided with an homogenous, profuse, and purely cholinergic innervation (Feldberg et al, 1940). Preliminary experiments showed that the electric organ contains a very high amount of thiamine (Eder et al, 1976), and histofluorescence analysis revealed that most of the vitamin is associated with nerve trunks and nerve endings (Eder et al, 1978).…”

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confidence: 99%

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Thiamine and Cholinergic Transmission in the Electric Organ of Torpedo

Eder

Dunant²

1980

Journal of Neurochemistry

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The electric organ of Torpedo marmorata was found to contain as much as 120 +/- 24 nmol of thiamine per g of fresh tissue. The vitamin was distributed as nonesterified thiamine (32%), thiamine monophosphate (22%), thiamine diphosphate (8%), and an important proportion of thiamine triphosphate (38%). A high level of thiamine triphosphate was found in synaptosomes isolated from the electric organ. In contrast, the synaptic vesicles did not show any enrichment in thiamine, whereas they contained a marked peak of acetylcholine (ACh) and ATP. Thus thiamine seems to be very abundant in cholinergic nerve terminals; its localization is apparently extravesicular, either in the axoplasm or in association with plasma membrane. When calcium was reduced and magnesium increased in the external medium, the efficiency of transmission was diminished, owing to inhibition of ACh release; in a parallel manner the degree of thiamine phosphorylation was found to increase--this condition is known to modify the repartition of ACh between vesicular and extravesicular compartments. Electrical stimulation, which causes periodic variations of the level of ACh and ATP, also caused significant changes in thiamine esters. In addition, related changes of the vitamin and the transmitter were observed under other conditions, suggesting a functional link between the metabolism of thiamine and that of ACh in cholinergic nerve terminals.

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