title: Effects of Deltamethrin on crayfish motor axon activity and neuromuscular transmission.
abstract: Deltamethrin (DM) is a widely used pesticide known to target sodium channels. Although this compound has been studied extensively at molecular and behavioral levels, the detailed action of DM on cellular and synaptic function is less well documented. In this report, we show that DM at nanomolar concentrations can silence tonic motor output of the crayfish ventral superficial flexor (VSF) within ∼10 min. Action potential (AP) amplitude was consistently reduced before silencing occurred, whereas AP duration and AP firing frequency did not change. In some synapses EPSP amplitude and synaptic delay were modified by DM, but the direction of change was not consistent. In order to better understand these diverse effects, intracellular recordings from motor axons of the crayfish opener were used for a detailed analysis. DM caused an initial, slow depolarization of resting membrane potential (Vm), which was accompanied by reduced AP amplitude but not AP duration. Resting Vm then underwent a step depolarization of ∼20 mV, which we propose corresponds to the onset of the depolarization block. In addition, DM shifted the AP initiation site in some opener axons during prolonged firing. This shift occurred concomitantly with a reduction in synaptic delay. A similar reduction in synaptic delay was also detected at some VSF axons, and can be attributed to the same mechanism. Results reported here suggest that DM at low concentrations result in: (i) depolarization block of motor axons before changes in network output can be detected, (ii) variable effects on synaptic transmission, with this variability presumably due to the diverse morphology and excitability of motor axons.
authors: Department of Biology, Boston University, United States.
authors: Linlin
authors: L
authors: Meng
authors: Department of Biology, Boston University, United States.
authors: Pierre-Francois N R
authors: PF
authors: Meyer
authors: Department of Biology, Boston University, United States.
authors: Meghan L
authors: ML
authors: Leary
authors: Department of Biology, Boston University, United States.
authors: Yussef F
authors: YF
authors: Mohammed
authors: Department of Biology, Boston University, United States.
authors: Shelbi D
authors: SD
authors: Ferber
authors: Department of Biology, Boston University, United States. Electronic address: jenwelin@bu.edu.
authors: Jen-Wei
authors: JW
authors: Lin
mesh_terms: D000200:Action Potentials; D000818:Animals; D003400:Astacoidea; D001369:Axons / Q000187:drug effects* / Q000502:physiology; D005260:Female; D008297:Male; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000502:physiology; D009570:Nitriles / Q000494:pharmacology*; D010575:Pesticides / Q000494:pharmacology*; D011722:Pyrethrins / Q000494:pharmacology*; D009435:Synaptic Transmission / Q000187:drug effects*
chemical_list: D009570:Nitriles; D010575:Pesticides; D011722:Pyrethrins; C017180:decamethrin
keywords: Action potential; Crayfish; Opener; Synaptic transmission; Ventral superficial flexor