scholarly journals Metabolism of acetylcholine in the nervous system of Aplysia californica. II. Reginal localization and characterization of choline uptake.

1975 ◽  
Vol 65 (3) ◽  
pp. 275-291 ◽  
Author(s):  
M L Eisenstadt ◽  
S N Treistman ◽  
J H Schwartz
Keyword(s):  
Nervous System ◽  
Nervous Tissue ◽  
Aplysia Californica ◽  
Nerve Terminals ◽  
Choline Uptake ◽  
Physiological Conditions ◽  
High Affinity ◽  
Complicated Manner ◽  
Cholinergic Cell

The choline required for synthesis of acetylcholine is derived exogenously by Aplysia ganglia. Under physiological conditions choline was taken up primarlily by neuropile and nerves and not by cholinergic cell bodies. In addition, compared with their contents of choline acetyltransferase, those components of nervous tissue which contain nerve terminals and axons synthesized acetylcholine far more efficiently. Choline was accumulated by high and low affinity uptake processes; the high affinity process appeared to be characteristic of cholinergic nuerons (Swartz, J. H., M. L. Eisenstadt, and H. Cedar.1975. J. Gen. Physiol. 65:255). The two uptake processes were similarly affected by temperature with a Q10 of 2.8. Both were dependent on a variety of ions in a complicated manner. High affinity uptake seemed to be more dependent on Na+, showed greater inhibition by ouabain, and was selectively inhibited by oxotremorine. We found that the functional state of neurons did not alter uptake of radioactive choline by either process, nor did it change the conversion to radioactive acetylcholine.

scholarly journals Metabolism of acetylcholine in the nervous system of Aplysia californica. I. Source of choline and its uptake by intact nervous tissue.

1975 ◽  
Vol 65 (3) ◽  
pp. 255-273 ◽  
Author(s):  
J H Schwartz ◽  
M L Eisenstadt ◽  
H Cedar
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Nervous Tissue ◽  
Aplysia Californica ◽  
The Other ◽  
Michaelis Constant ◽  
High Affinity ◽  
The Central Nervous System

Although acetylcholine is a major neurotransmitter in Aplysia, labeling studies with methionine and serine showed that little choline was synthesized by nervous tissue and indicated that the choline required for the synthesis of acetylcholine must be derived exogenously. Aanglia in the central nervous system (abdominal, cerebral, and pleuropedals) all took up about 0.5 nmol of choline per hour at 9 muM, the concentration of choline we found in hemolymph. This rate was more than two orders of magnitude greater than that of synthesis from the labeled precursors. Ganglia accumulated choline by a process which has two kinetic components, one with a Michaelis constant between 2-8 muM. The other component was not saturated at 420 muM. Presumably the process with the high affinity functions to supply choline for synthesis of transmitter, since the efficiency of conversion to acetylcholine was maximal in the range of external concentrations found in hemolymph.

Acid-Sensing Ion Channels

2020 ◽  
Author(s):  
Stefan Gründer
Keyword(s):  
Nervous System ◽  
Ion Channels ◽  
Excitatory Synapses ◽  
Detailed Characterization ◽  
High Affinity ◽  
Acid Sensing Ion Channels ◽  
Long Time ◽  
Pathological Pain

Acid-sensing ion channels (ASICs) are proton-gated Na+ channels. Being almost ubiquitously present in neurons of the vertebrate nervous system, their precise function remained obscure for a long time. Various animal toxins that bind to ASICs with high affinity and specificity have been tremendously helpful in uncovering the role of ASICs. We now know that they contribute to synaptic transmission at excitatory synapses as well as to sensing metabolic acidosis and nociception. Moreover, detailed characterization of mouse models uncovered an unanticipated role of ASICs in disorders of the nervous system like stroke, multiple sclerosis, and pathological pain. This review provides an overview on the expression, structure, and pharmacology of ASICs plus a summary of what is known and what is still unknown about their physiological functions and their roles in diseases.

Characterization of a high-affinity choline uptake mechanism in the cestode Hymenolepis diminuta

1991 ◽  
Vol 69 (3) ◽  
pp. 369-377 ◽  
Author(s):  
Rodney A. Webb
Keyword(s):  
Hymenolepis Diminuta ◽  
Choline Uptake ◽  
Uptake Mechanism ◽  
Tissue Slices ◽  
High Affinity ◽  
Sodium Gradient ◽  
Sodium Dependent ◽  
Wet Weight ◽  
High Affinity Choline Transporter

Radiolabelled choline was taken up by tissue slices of the cestode Hymenolepis diminuta by a sodium-dependent and a sodium-independent mechansim. The sodium-dependent uptake was saturable, against a concentration gradient, displayed structural specificity, and was inhibited, in part, by hemicholinium-3. Kinetic analysis of the sodium-dependent choline uptake showed an apparent Kt = 2.0 μM and a Vmax = 0.146 pmol∙mg−1 wet weight tissue∙min−1, which is consistent with a high-affinity choline uptake (HAChU) mechanism. The rate of uptake or release of choline depended on the magnitude and direction of the sodium gradient, was diminished by high- or low-potassium, but was not chloride or sulphate dependent. A homoexchange mechanism for HAChU was not demonstrated. Evidence was obtained to suggest that HAChU or release of endogenous ACh is regulated by autoreceptors. The choline taken up by the HAChU mechanism was but slowly converted to ACh and other products.Key words: high-affinity sodium-dependent choline uptake, sodium-independent choline uptake, cestode tissue slices, choline metabolism, high-affinity choline transporter.

scholarly journals Identification and Characterization of a High-Affinity Choline Uptake System of Brucella abortus

2012 ◽  
Vol 195 (3) ◽  
pp. 493-501 ◽  
Author(s):  
C. K. Herrmann ◽  
L. Bukata ◽  
L. Melli ◽  
M. I. Marchesini ◽  
J. J. Caramelo ◽  
...  
Keyword(s):  
Brucella Abortus ◽  
Choline Uptake ◽  
Uptake System ◽  
High Affinity ◽  
Identification And Characterization
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