EFFECTS OF CARBARYL, PERMETHRIN, 4-NONYLPHENOL, AND COPPER ON MUSCARINIC CHOLINERGIC RECEPTORS IN BRAIN OF SURROGATE AND LISTED FISH SPECIES

We investigated the regulation of the muscarinic cholinergic receptor (MChR) in brain from seven species of fish, two surrogates and five th reatened or endangered species exposed to a series of chemicals as a m easure of compensatory response among species. Fish were classified as either cold water (rainbow trout-surrogate, apache trout, lahanton tr out) or warm water (fathead minnow-surrogate, razorback sucker, bonyta il chub, colorado squawfish) and were exposed to chemicals shown to af fect cholinergic pathways (carbaryl and permethrin) and two chemicals whose relationships to the cholinergic system is less clear (4-nonylph enol and copper). Downregulation of MChR occurred in all warm water sp ecies, except colorado squawfish, and at carbaryl concentrations simil ar to those causing downregulation observed in rainbow trout. Permethr in exposure resulted in downregulation in fathead minnow and razorback sucker, but the concentrations required for observation of this pheno menon were much greater than observed in cold water species. Copper ex posure caused a decrease in brain MChR in rainbow trout and apache tro ut, whereas 4-nonylphenol exposure resulted in a decrease in brain MCh R in all three cold water species. Our results indicate that surrogate s are useful in assessing sublethal physiological responses to chemica ls with a known mechanism of action such as carbaryl and support use o f surrogates for assessing physiological responses to chemicals with d iverse, less clear mechanisms of action. (C) 1998 Elsevier Science Inc . All rights reserved.