Tetrahydropapaveroline and salsolinol alter45Ca2+ efflux within perfused hippocampus of unrestrained rats |
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Authors: | R D Myers T H Privette R L Hornsby H S Swartzwelder |
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Institution: | (1) Departments of Pharmacology and Psychiatric Medicine, School of Medicine, East Carolina University, 27858 Greenville, NC;(2) UNC School of Medicine, 27514 Chapel Hill, NC;(3) Present address: VA Medical Center, 27701 Durham, NC |
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Abstract: | The kinetics of45Ca2+ efflux were examined at circumscribed sites in the perfused hippocampus of the freely moving rat with either one of two tetrahydroisoquinoline (TIQ) products, tetrahydropapaveroline (THP) or salsolinol. Guide tubes for unilateral push-pull perfusion were implanted stereotaxically to rest just above sites within the dorsal hippocampus. Upon recovery from surgery, a tissue site in the hippocampus was prelabeled with 1.0 l of45Ca2+ (2.0 Ci) injected through the indwelling guide tube. After 16–20 hr had elapsed, successive push-pull perfusions of the site were carried out with an artificial cerebrospinal fluid (CSF), at 5.0 min intervals and at a rate of 20 l/min, in order to obtain a control washout curve of declining radioactivity. On the fifth of a series of 5.0 min perfusions, either THP or salsolinol was added to the perfusion medium in a concentration of 10 or 100 ng/ l. Then the hippocampal site was perfused again with control CSF for the collection of an additional three samples. Although THP in both of the test concentrations generally augmented the efflux of45Ca2+, the temporal course and magnitude of the enhancement depended on the anatomical site of the perfusion. In the more rostral hippocampal planes of AP 3.0 and AP 4.0, THP caused a delayed efflux of the cation, after the perfusion of THP had been discontinued, in nearly half of the loci reactive to the TIQ. Similarly, salsolinol enhanced significantly the efflux of45Ca2+ in a concentration-dependent manner during the interval of its perfusion within the hippocampal plane of AP 3.0. These results suggest that both THP and salsolinol can affect differentially the kinetics of45Ca2+ efflux and that these differences are contingent on the circumscribed anatomical site of push-pull perfusion. It is envisaged that a part of the neurochemical effects of the two TIQs when acting centrally are mediated by membrane mechanisms involving Ca2+ transport, metabolism or other cellular activity of the cation. |
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Keywords: | Calcium tetrahydropapaveroline (THP) salsolinol push-pull perfusion amine-aldehyde adduct tetrahydroisoquinoline (TIQ) |
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