Cholinesterases in the Carotid Body of the Cat as seen with the Electron Microscope

Jones, J V; Ballard, Kathleen J.

doi:10.1038/newbio233146a0

Cited by 3 publications

(2 citation statements)

References 7 publications

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“…In the ensuing decades, numerous studies investigated the role of ACh in chemosensation and demonstrated that small quantities of cholinergic agonists and antagonists profoundly altered chemoreceptor discharge 20. Neurochemical investigations indicated that the metabolic machinery necessary for ACh synthesis, storage and inactivation appear to be associated with type I cells in the carotid body 2,3,23,24,31,35,36 and that afferent fibers of the CSN are nearly devoid of cholinergic activity23, 28. In addition, it has been demonstrated that an ACh-like substance is released upon stimulation of the organ in vitrol7, Is.…”

Section: Introductionmentioning

confidence: 99%

Localization and function of cat carotid body nicotinic receptors

et al. 1985

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Key words: acetylcholine --a-bungarotoxin --autoradiography --carotid body --dopamine release --nicotinic receptors Acetylcholine and nicotinic agents excite cat carotid body chemoreceptors and modify their response to natural stimuli. The present experiments utilized [125I]a-bungarotoxin ([125I]a-BGT) to localize within the chemosensory tissue the possible sites of action of exogenous and endogenous nicotinic cholinergic substances. In vitro equilibrium binding studies of intact carotid bodies determined a K d of 5.57 nM and a Bma x of 9.21 pmol/g of tissue. Chronic section (12-15 days) of the carotid sinus nerve (CSN) did not change the amount of displaceable toxin binding. In contrast, the specific binding was reduced by 46% following removal of the superior cervical ganglion. Light microscope autoradiography of normal, CSN-denervated and sympathectomized carotid bodies revealed displaceable binding sites concentrated in lobules of type I and type II cells. Treatment of carotid bodies with 50 nM a-BGT in vitro reduced by 50% the release of [3H]dopamine (synthesized from [3H]tyrosine) caused by hypoxia or nicotine, and also significantly reduced the stimulus-. evoked discharges recorded from the CSN. The data suggest (1) an absence of ct-BGT binding sites on the afferent terminals of the CSN and (2) that nicotinic receptors located within parenchymal cell lobules may modulate the release of catecholamines from these cells.

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Section: Introductionmentioning

confidence: 99%

Localization and function of cat carotid body nicotinic receptors

et al. 1985

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“…Biscoe & Silver (1966) combined their histochemical studies with nerve degeneration experiments in an attempt to localize the sites of enzyme activity more accurately at the light microscopical level but a study of the fine structural localization of the enzyme is necessary for a clearer understanding of its possible role in the carotid body. Preliminary results of this study have already been published elsewhere (Jones & Ballard, 1971).…”

Section: Introductionmentioning

confidence: 90%

The fine structural localization of cholinesterases in the carotid body of the cat

Ballard¹,

Jones²

1971

The Journal of Physiology

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1. The distribution of cholinesterases in the carotid body of the cat has been investigated with the electron microscope to obtain a clearer picture of the localization of the enzyme. This is of relevance to the possible role of acetylcholine as a transmitter in the carotid body. 2. Tissues were fixed for short periods and incubated by the method of Karnovsky for the fine localization of cholinesterases. 3. The enzyme was found in two main sites. Butyrylcholinesterase was present on the type II cell membrane while acetylcholinesterase was found in groups of peripheral axons. No intracellular enzyme was found. 4. It is concluded that acetylcholine may be a transmitter in the carotid body and that it may be partly destroyed by enzymic hydrolysis. A possible explanation for some of the anomalous pharmacological findings is suggested.

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Demonstration of choline acetyltransferase activity in the carotid body of the cat

Ballard¹,

Jones²

1972

The Journal of Physiology

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1. The distribution of choline acetyltransferase in the carotid body of the cat has been investigated with the electron microscope to determine sites of enzymic activity. This is of relevance to the possible role of acetylcholine as a transmitter in the carotid body. 2. Tissues were fixed for short periods and incubated by the method of Kasa, Mann & Hebb, for the fine structural localization of choline acetyltransferase. 3. The enzyme was found in the cytoplasm of the type I cells and seemed to be associated with vesicles. No enzyme was found in the large nerve endings synapsing with the type I cell. 4. Whole carotid bodies were assayed for their choline acetyltransferase activity and significant amounts were found. 5. It is concluded that acetylcholine may be a transmitter in the carotid body and that it is synthesized in type I cells. A possible mode of initiation of chemoreceptor afferent impulses is suggested.

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Cholinesterases in the Carotid Body of the Cat as seen with the Electron Microscope

Cited by 3 publications

References 7 publications

Localization and function of cat carotid body nicotinic receptors

Localization and function of cat carotid body nicotinic receptors

The fine structural localization of cholinesterases in the carotid body of the cat

Demonstration of choline acetyltransferase activity in the carotid body of the cat

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