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A Synaptosomal Preparation from the Guinea Pig Ileum Myenteric Plexus
Author(s) -
Briggs Clark A.,
Cooper Jack R.
Publication year - 1981
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1981.tb01705.x
Subject(s) - myenteric plexus , guinea pig , ileum , chemistry , neuroscience , anatomy , medicine , biology , endocrinology , biochemistry , immunohistochemistry
Abstract: Our interest in investigating the presynaptic modulation of acetylcholine release led to the development of a synaptosomal preparation from the guinea pig ileum myenteric plexus‐longitudinal muscle. A crude synaptosomal fraction (P 2 ) was obtained by homogenization and differential centrifugation. The preparation exhibited a specific uptake system for choline and for nor‐adrenaline (NA), but not for 5‐hydroxytryptamine (5‐HT). Synaptosomes were isolated from this P 2 fraction by an isoosmotic density gradient prepared from sucrose and metrizamide. The resultant synaptosomal fraction was enriched about sevenfold in both choline uptake and in choline acetyltransferase (ChAT). Choline was transported by a high‐affinity system with a K m of 6.5 × 10 −7 M and a V max of 41 pmol/mg protein/min. Electron microscopy confirmed the synaptosomal nature of the gradient fraction. Some synaptosomal profiles contained only small, translucent vesicles whereas others also contained large (approx. 100 nm diameter) electron‐opaque vesicles. The crude synaptosomal fraction synthesized acetylcholine (ACh) from exogenous choline and it released the synthesized ACh in a calcium‐dependent manner.