Brain Research 864 (2000) 312–314 www.elsevier.com / locate / bres Short communication 1 BgK anemone toxin inhibits outward K currents in snail neurons b a a a b Anoland Garateix , Rosario Vega , Emilio Salceda , Jorge Cebada , Abel Aneiros , a, * Enrique Soto a ´ ´ Instituto de Fisiologıa-BUAP , Universidad Autonoma de Puebla, Apartado Postal 406, Puebla, Pue. 72000, Mexico b ´ ´ Departamento de Bioactivos y Productos Naturales Marinos, Instituto de Oceanologıa, Ministerio de Ciencia, Tecnologıa y Medio Ambiente, La Habana, Cuba Accepted 7 February 2000 Abstract 1 We studied the effects of BgK toxin on outward K currents in isolated neurons of the snail Helix aspersa, using the whole cell patch 1 clamp technique. BgK partially and reversibly blocked K currents in the 1 pM to 100 nM concentration range ( n553). The dose–response curve for BgK current inhibition had a maximum blocking effect at 100 nM. Our results indicate that BgK is a potent, 1 apparently non-selective, K channel blocker in molluscan neurons.  2000 Elsevier Science B.V. All rights reserved. Themes: Excitable membranes and synaptic transmission Topics: Potassium channel physiology, pharmacology, and modulation Keywords: Marine toxins; Neurotoxin; Potassium channel; Helix aspersa; Bunodosoma granulifera; BgK Several peptide toxins exert actions on potassium chan- BgK action and its selectivity on the voltage-activated nels. Among the sea anemone toxins with an action on outward potassium currents of isolated snail neurons. 1 voltage-gated K channels, BgK obtained from Toxin was obtained from sea anemone Bunodosoma Bunodosoma granulifera is a peptide of 37 amino acids granulifera as originally described by Aneiros et al. [2]. In (4273 Da molecular mass) that represents a new structural some of the experiments (specified), we have used syn- 125 type of potassium channel toxin. BgK displaces I-a- thetic BgK which was kindly provided to us by Prof. ´ ´ dendrotoxin from its binding sites on rat brain synaptosom- Andre Menez. al membranes with an apparent K of 0.7 nM, and Neurons were enzymatically dissociated from the peri- i 1 suppresses K currents in rat dorsal root ganglion neurons esophageal ganglion of land snail Helix aspersa using in culture [2]. In recordings of whole cell currents in trypsin (2 mg/ml). Isolated cells were placed in the Xenopus oocytes BgK blocks the KV1 channels, while the recording chamber (400 ml) on an inverted microscope 1 KV3.1 were insensitive to the toxin [4], thus suggesting stage and perfused with Na -free extracellular solution (in 1 that BgK has some selectivity between different K mM: choline Cl, 70; KCl, 4; MgCl , 5; CaCl , 7; CdCl , 2 2 2 channels. 0.5; Hepes, 5; pH 7.4) at a rate of 500 ml / min. Toxin was Information about the characteristics of BgK interactions delivered by pressure ejection at a flow rate of 20 ml/min 1 with native K channels is scarce. It now seems appro- close to the cell under study (at about 40–80 mm). 1 priate to examine its action on specific K currents in Whole-cell currents were recorded at room temperature order to define its selectivity and potency. In this work, we (22–258C), according to the method described by Hamill used the whole cell voltage clamp technique to study the et al. [5]. Patch pipettes had resistances of 1–2 MV when filled with the intracellular solution (in mM: KCl, 80; CaCl , 0.02; Hepes, 20; EGTA, 1; pH 7.4). Command 2 pulse generation and data sampling ( ¯25 ms) were con- trolled by the Pclamp 5.5 software (Axon Inst.) using a *Corresponding author Tel.: 152-2-244-8811; fax: 152-2-233-4511. E-mail address: esoto@siu.buap.mx (E. Soto) 12-bit analog to digital converter (LabMaster-DMA). 0006-8993 / 00 / $ – see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0006-8993(00)02131-4