title: Acetylcholine release and choline uptake by cuttlefish (Sepia officinalis) optic lobe synaptosomes.
abstract: Acetylcholine (ACh), which is synthesized from choline (Ch), is believed to hold a central place in signaling mechanisms within the central nervous system (CNS) of cuttlefish (Sepia officinalis) and other coleoid cephalopods. Although the main elements required for cholinergic function have been identified in cephalopods, the transmembrane translocation events promoting the release of ACh and the uptake of Ch remain largely unsolved. The ACh release and Ch uptake were quantitatively studied through the use of in vitro chemiluminescence and isotopic methods on a subcellular fraction enriched in synaptic nerve endings (synaptosomes) isolated from cuttlefish optic lobe. The ACh release evoked by K+ depolarization was found to be very high (0.04 pmol ACh.s(-1).mg(-1) protein). In response to stimulation by veratridine, a secretagogue (a substance that induces secretion) that targets voltage-gated Na+ channels, the release rate and the total amount of ACh released were significantly lower, by 10-fold, than the response induced by KCl. The high-affinity uptake of choline was also very high (31 pmol Ch.min(-1).mg(-1) protein). The observed ACh release and Ch uptake patterns are in good agreement with published data on preparations characterized by high levels of ACh metabolism, adding further evidence that ACh acts as a neurotransmitter in cuttlefish optic lobe.
authors.affiliation: CESAM, Departamento de Biologia, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: M Alexandra
authors.initials: MA
authors.lastname: Nunes
authors.forename: Sofia
authors.initials: S
authors.lastname: Santos
authors.forename: J Miguel
authors.initials: JM
authors.lastname: Cordeiro
authors.forename: Paulo
authors.initials: P
authors.lastname: Neves
authors.forename: Virgília S
authors.initials: VS
authors.lastname: Silva
authors.forename: António
authors.initials: A
authors.lastname: Sykes
authors.forename: Fernando
authors.initials: F
authors.lastname: Morgado
authors.forename: Yves
authors.initials: Y
authors.lastname: Dunant
authors.forename: Paula P
authors.initials: PP
authors.lastname: Gonçalves
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002794:Choline / Q000378:metabolism*; D009899:Optic Lobe, Nonmammalian / Q000187:drug effects / Q000378:metabolism*; D011189:Potassium Chloride; D049833:Sepia / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism*; D014701:Veratridine / Q000494:pharmacology
chemical_list: D011189:Potassium Chloride; D014701:Veratridine; D002794:Choline; D000109:Acetylcholine