Rapid neurobehavioral analysis of Pfiesteria piscicida effects in juvenileand adult rats

The estuarine dinoflagellate Pfiesteria piscicida is known to kill fish and has been associated with neurocognitive deficits in humans. We have develo ped a rat model to demonstrate that exposure to Pfiesteria causes significa nt learning impairments. This has been repeatedly seen as a choice accuracy impairment during radial-arm maze learning, Pfiesteria-induced effects wer e also seen in a locomotor activity test in the figure-8 apparatus. The cur rent studies used the short-term radial-arm maze acquisition, the figure-8 activity test, and the functional observational battery (FOB) to assess Pfi esteria-induced neurobehavioral effects in adult and juvenile rats. In stud y 1, the neurobehavioral potency of three different Pfiesteria cultures (Pf 113, Pf 728, and Pf Vandermere) was assessed. Ninety-six (12 per group) ad ult female Sprague-Dawley rats were injected subcutaneously with a single d ose of Pfiesteria taken from aquarium-cultured Pfiesteria (35,600 or 106,80 0 Pfiesteria cells per kilogram of rat body weight). One control group (N = 12) was injected with saline and one (N = 12) with aquarium water not cont aining Pfisteria. All three of the Pfiesteria samples (p < 0.05) impaired c hoice accuracy over the first six sessions of training. At the time of the radial-arm maze choice accuracy impairment, no overt Pfiesteria-related eff ects were seen using an FOE, indicating that the Pfiesteria-induced choice accuracy deficit was not due to generalized debilitation. In the figure-8 a pparatus, Pfiesteria treatment caused a significant decrease in mean locomo tor activity. In study 2, the neurobehavioral effects of the Pf 728 sample type were assessed in juvenile rats. Twenty-four day-old male and female ra ts were injected with 35,600 or 106,800 Pf-728 Pfiesteria cells per kilogra m of rat body weight. As with adult females, the juvenile rats showed a sig nificant impairment in radial-arm maze choice accuracy. No changes in locom otor activity or the FOE were detected in the juvenile rats. Furthermore, t here were no differences between male and female rats in the Pfiesteria-ind uced choice accuracy impairment. Pfiesteria effects on choice accuracy in t he radial-arm maze in rats constitute a critical component of the model of Pfiesteria toxicity, because the hallmark of Pfiesteria toxicity in humans is cognitive dysfunction. Our finding that analysis of the first six sessio ns of radial-arm maze testing is sufficient for determining the effect mean s that this test will be useful as a rapid screen for identifying the criti cal neurotoxin(s) of Pfiesteria in future studies. (C) 2000 Elsevier Scienc e Inc. All rights reserved.