title: Learning impairment caused by a toxin produced by Pfiesteria piscicida infused into the hippocampus of rats.
abstract: Pfiesteria piscicida, an estuarine dinoflagellate, which has been shown to kill fish, has also been associated with neurocognitive deficits in humans. With a rat model, we have demonstrated the cause-and-effect relationship between Pfiesteria exposure and learning impairment. In several studies, we have replicated the finding in Sprague-Dawley rats that exposure to fixed acute doses of Pfiesteria cells or filtrates caused radial-arm maze learning impairment. Recently, this finding of Pfiesteria-induced learning impairment in rats has been independently replicated in another laboratory as well. We have demonstrated significant Pfiesteria-induced learning impairment in both the win-shift and repeated-acquisition tasks in the radial-arm maze and in reversal learning in a visual operant signal detection task. These learning impairments have been seen as long as 10 weeks after a single acute exposure to Pfiesteria. In the current study, we used a hydrophilic toxin isolated from clonal P. piscicida cultures (PfTx) and tested its effect when applied locally to the ventral hippocampus on repeated acquisition of rats in the radial-arm maze. Toxin exposure impaired choice accuracy in the radial-arm maze repeated acquisition procedure. The PfTx-induced impairment was seen at the beginning of the session and the early learning deficit was persistent across 6 weeks of testing after a single administration of the toxin. Eventually, with enough practice, in each session, the PfTx-exposed rats did learn that session's problem as did control rats. This model has demonstrated the cause-and-effect relationship between exposure to a hydrophilic toxin produced by P. piscicida and learning impairment, and specifically that the ventral hippocampus was critically involved.
authors.affiliation: Department of Psychiatry and Behavioral Science, Duke University Medical Center, Durham, NC 27710, USA. edlevin@duke.edu
authors.forename: Edward D
authors.initials: ED
authors.lastname: Levin
authors.forename: W Paul
authors.initials: WP
authors.lastname: Blackwelder
authors.forename: Howard B
authors.initials: HB
authors.lastname: Glasgow
authors.forename: JoAnn M
authors.initials: JM
authors.lastname: Burkholder
authors.forename: Peter D R
authors.initials: PD
authors.lastname: Moeller
authors.forename: John S
authors.initials: JS
authors.lastname: Ramsdell
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000382:microbiology*; D007859:Learning Disabilities / Q000209:etiology*; D018782:Maze Learning / Q000187:drug effects; D009498:Neurotoxins / Q000633:toxicity*; D020045:Pfiesteria piscicida / Q000378:metabolism*; D011529:Protozoan Infections, Animal / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time; D013997:Time Factors
chemical_list: D009498:Neurotoxins