[Different localization of L-type and N-type activated calcium channels in the brain tissue cells in rabbits]

Postsynaptosomal, microsomal (HMF), and synaptosomal fractions were isolated from rabbit brain tissue according to two different protocols. The binding of 1,4-dihydropyridines and transport of 45Ca2+ indicated the presence of L-type of voltage operated calcium channels (VOCC) in the postsynaptosomal and microsomal membranes. The 200 kD protein, which bound 1,4-dihydropyridines and transported 45Ca2+, was identified as alpha-subunit of L-type VOCC. The authors further showed that after centrifugation of synaptosomal proteins into sucrose density gradient the fraction of proteins which sedimented in 1.10(1) mol/l sucrose was able to bind 125I-omega-conotoxin GVIA. The separation of these proteins in 6% PAGE resulted in proteins of Mw from 40 to 200 kD. The 170 kD protein extracted from PAGE bound omega-conotoxin along with 45-65 kD proteins, which are supposed to be subunits of the neuronal acetylcholine receptor. (Fig. 6, Ref. 15.).