Assessment of saxitoxin sensitivity of nerves isolated from the Pacific oyster, Crassostrea gigas, exposed to Alexandrium minutum

• Published in: Toxicon
• Main Authors: Boullot, Floriane, Fabioux, Caroline, Hegaret, Helene, Soudant, Philippe, Boudry, Pierre, Benoit, Evelyne
• Other Authors: Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut des Neurosciences Paris-Saclay (NeuroPSI), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Service d'Ingénierie Moléculaire pour la Santé (ex SIMOPRO) (SIMoS), Médicaments et Technologies pour la Santé (MTS), Université Paris-Saclay-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Paris-Saclay-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2017
• Subjects: Crassostrea gigas; Compound nerve action potential; Alexandrium minutum; Paralytic shellfish toxins; ACTI; [SDV]Life Sciences [q-bio]; [SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]; [SDV.NEU.NB]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Neurobiology; [SDV.TOX]Life Sciences [q-bio]/Toxicology; Pacific; Pacific oyster
• Online Access: https://hal.archives-ouvertes.fr/hal-02334360; https://doi.org/10.1016/j.toxicon.2017.12.025

International audience Harmful algal blooms of the genus Alexandrium, producing paralytic shellfish toxins (PSTs), regularly occur in French coastal waters, contaminating shellfish. Among those, Pacific oysters (Crassostrea gigas) may accumulate high levels of PSTs during these blooms. PSTs are composed of saxitoxin (STX) and analogues which, similarly to tetrodotoxin, block voltage-gated sodium channels and thus inhibit action potentials in excitable cells. The aim of our study was to analyse the PST-sensitivity of C. gigas in relation to toxin bio-accumulation. For this purpose, the STX sensitivity of cerebrovisceral nerves isolated from both field and cultured oysters obtained from a shellfish farmer, experimentally exposed to A. minutum, was evaluated using an electrophysiological approach. Meanwhile, the PST content of their digestive gland was determined using biochemical analyses.The compound nerve action potential (CNAP) of oysters collected in the field on April 2014 was about 5 fold more sensitive to STX than those collected on October 2015, suggesting that summer exposure to PST-producing A. minutum bloom potentially resulted in a decreased sensitivity to STX. Additionally, the STX-sensitivity of CNAPs recorded from cultured oysters experimentally fed with A. minutum (toxic-exposed oysters) or Isochrysis sp., a non-toxic micro-algae, (control oysters) revealed that these oysters could be separated into two groups, “resistant” and relatively “sensitive”, independently of their diet. Moreover, the percentage of toxin-“sensitive” nerves was lower and the STX concentration necessary to block 50% of their CNAP was higher in toxic-exposed than control oysters. This supports the above proposed hypothesis stating that toxic-exposed oysters are relatively more resistant to STX than non-exposed ones. However, no obvious correlation was observed between nerve sensitivity to STX and the PST content of oyster digestive gland.In conclusion, C. gigas oyster nerves are shown, for the first time, to have micromolar ...