AbstractAntisense oligodesoxynucleotides were used to determine whether the mediatophore proteolipid is necessary for the Ca2+‐dependent release of the neurotransmitter acetylcholine.Xenopus laevisoocytes were injected with poly(A)+mRNAs extracted from the electric lobes ofTorpedo marmorata.The electric lobes contain an homogeneous population of cholinergic neurons homologous to motoneurons. Addition of antisense probes hybridizing to the mediatophore 15 kDa subunit inhibited the expression of both the mediatophore proteolipid in oocyte membranes and the Ca2+‐dependent acetylcholine release. Expression of other neuronal functions such as synthesis of 14Cacetylcholine from 14Cacetate was not inhibited. Another antisense probe specific for the sequence of a related proteolipid cDNA (the 15 kDa subunit of the chromaffin granule protonophore) was used as a control. It did not hybridize with theTorpedomediatophore mRNA and, injected in addition to electric lobe mRNAs, it did not inhibit either mediatophore expression or acetylcholine release. We showed in addition that the mRNA primed oocytes did not contain a vesicular pool of acetylcholine. It was concluded (i) that the mediatophore proteolipid is essential for Ca2+‐dependent acetylcholine release and (ii) that the cytosolic pool of neurotransmitter seems to be preferentially used in this s
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