Cellular accumulation of amines and amino acids in the central ganglia of a gastropod mollusc,Planorbis corneus: An autoradiographic study

1978 ◽  
Vol 7 (6) ◽  
pp. 759-776 ◽  
Author(s):  
J. D. Turner ◽  
G. A. Cottrell
Keyword(s):  
Amino Acids ◽  
Autoradiographic Study ◽  
Gastropod Mollusc ◽  
Cellular Accumulation ◽  
Planorbis Corneus

Problems associated with the use of tetraethylammonium to test for monosynaptic connexions

1975 ◽  
Vol 62 (3) ◽  
pp. 797-803
Author(s):  
M. S. Berry ◽  
V. W. Pentreath
Keyword(s):  
Nervous System ◽  
Transmitter Release ◽  
Gastropod Mollusc ◽  
Postsynaptic Response ◽  
Postsynaptic Potential ◽  
Planorbis Corneus

Several investigators of the molluscan nervous system have used TEA, injected into presynptic neurones, to determine whether the connexions made by these neurones are monosynaptic. The increase in spike duration produced by the TEA causes an increase in transmitter release, and hence an increase in the amplitude of the postsynaptic potential if the connexion is direct. If the connexion is indirect, the spike in an intercalated neurone will not be affected by the TEA, and the postsynaptic response will remain constant. Experiments described here show that TEA can cross electrotonic junctions in the gastropod mollusc Planorbis corneus. They also show that each TEA-prolonged presynaptic impulse may produce more than one postsynaptic impulse. A larger postsynaptic potential could therefore be produced by presynaptic injection of TEA in the case of an indirect connexion. This indicates that care must be taken when interpreting the results of experiments using TEA to test for monosynaptic connexions.

Further identification of multiple responses mediated by dopamine in the CNS of Planorbis corneus

1978 ◽  
Vol 56 (1) ◽  
pp. 7-18 ◽  
Author(s):  
J. F. MacDonald ◽  
M. S. Berry
Keyword(s):  
Neuroleptic Drugs ◽  
Intracellular Recordings ◽  
Excitatory Postsynaptic Potentials ◽  
Multiple Responses ◽  
Gastropod Mollusc ◽  
Postsynaptic Potentials ◽  
Synaptic Potentials ◽  
Inhibitory Postsynaptic Potentials ◽  
Planorbis Corneus ◽  
Synaptic Responses

Intracellular recordings from neurones, receiving monosynaptic contacts from a dopamine-containing (DA-containing) neurone in the central ganglia of the gastropod mollusc Planorbis corneus, revealed that there are at least three DA-mediated responses. These are 'fast' excitatory postsynaptic potentials (EfPSPs) (200 ms), 'slow' excitatory postsynaptic potentials (EsPSPs) (900 ms), and inhibitory postsynaptic potentials (IPSPs) (200–900 ms). Various combinations of these synaptic potentials were recorded from postsynaptic neurones: EsPSPs, EfPEPs, EsEfPSPs, or EfIPSPs. Neurones receiving such connections also responded appropriately to iontophoresized DA with a 'fast' depolarization (EfPSPs), a 'slow' depolarization (EsPSPs), or a hyperpolarization (IPSPs). These responses could be distinguished on the basis of function (excitation or inhibition), duration, rate of desensitization, and sensitivity to apomorphine, D-LSD, and tubocurarine. The neuroleptic drugs (DA antagonists) haloperidol, fluphenazine, and metoclopramide reduced both excitatory and inhibitory DA transmission. This investigation strongly supports the hypothesis that DA is the transmitter mediating multiple synaptic responses in Planorbis.

scholarly journals AUTORADIOGRAPHIC STUDY OF SUGAR AND AMINO ACID ABSORPTION BY EVERTED SACS OF HAMSTER INTESTINE

1965 ◽  
Vol 25 (2) ◽  
pp. 19-39 ◽  
Author(s):  
William B. Kinter ◽  
T. Hastings Wilson
Keyword(s):  
Amino Acids ◽  
Brush Border ◽  
Basal Membrane ◽  
Autoradiographic Study ◽  
Border Region ◽  
Transport Systems ◽  
Frozen Sections ◽  
Basal Pole ◽  
Everted Sacs

Autoradiographs were prepared from frozen sections of everted sacs of hamster jejunum which had been incubated in vitro with C14- or H3-labeled sugars and amino acids. When such tissue was incubated in 1 mM solutions of L-valine or L-methionine, columnar absorptive cells at tips of villi accumulated these amino acids to concentrations ranging from 5 to 50 millimoles per liter of cells. Quantitative data were obtained by microdensitometry of C14 autoradiographs. Similar, though less striking, results were obtained with the sugars: galactose, 3-0-methylglucose, α-methylglucoside, and 6-deoxyglucose. In all cases the marked "step-up" in concentration occurred near the brush border of the cell, and a "step-down" in concentration occurred at the basal pole of the cell. Known inhibitors of intestinal absorption, e.g., phlorizin in the case of sugars, blocked the concentrative step at the luminal border of the absorptive cell. It is inferred from these data that active transport systems for sugars and amino acids reside in the brush border region of the cell. Additional evidence suggests that the basal membrane of the cell may be the site of both a diffusion barrier and a weak transport system directed into the cell.

Intensification of the cellular accumulation of amino acids by pyridoxal

1953 ◽  
Vol 11 ◽  
pp. 303-304 ◽  
Author(s):  
Thomas R. Riggs ◽  
Barbara Coyne ◽  
Halvor N. Christensen
Keyword(s):  
Amino Acids ◽  
Cellular Accumulation
Sign in / Sign up

Export Citation Format

Share Document