Use of respiratory‐cardiovascular responses of rainbow trout (Oncorhynchus mykiss) in identifying acute toxicity syndromes in fish: Part 4. Central nervous system seizure agents

The respiratory‐cardiovascular responses of spinally transected rainbow trout to acutely lethal concentrations of chlorpyrifos, cypermethrin, fenvalerate, endosulfan, endrin, and strychnine were examined. Common to all six toxicants, the most striking change in respiratory‐cardiovascular parameters was an increased cough frequency. Ventilation frequency and volume dropped in strychnine‐exposed trout, but both remained near predose levels (frequency) or elevated (volume) in the pyrethroid‐ and cyclodiene‐exposed trout. In chlorpyrifos‐intoxicated trout, ventilation frequency decreased while volume increased. Oxygen consumption remained near predose levels in the chlorpyrifos‐, pyrethroid‐, and strychnine‐exposed trout, but increased dramatically in the cyclodiene‐exposed trout. Arterial oxygen, carbon dioxide, and pH declined in all the toxicant groups. In the pyrethroid‐ and strychnine‐exposed trout, hematocrit and hemoglobin levels tended to increase or remain constant during intoxication. Conversely, in the chlorpyrifos‐ and cyclodiene‐exposed trout, values for these parameters decreased. The responses for these pesticides (N= 23 fish) were combined with five fish acute toxicity syndromes (FATS) (N = 52 fish) previously described (non‐polar narcosis syndrome, polar narcosis syndrome, acetylcholinesterase inhibitor syndrome, respiratory uncoupler syndrome, and respiratory irritant syndrome) and assessed using discriminant function analyses. The final analysis resulted in 93% correct classification of the trout.