Selective breeding for sensitivity to DFP: generalization of effects beyond criterion variables

The degree of generalization to the effects of DFP, an organophosphate anticholinesterase, was studied in two lines of Sprague-Dawley derived rats selectively bred for varying sensitivities to DFP. In the S13, S14, S15, and S16 generations the Flinders S-line of rats were still more sensitive to the effects of DFP on the criterion variables upon which selection was based: core body temperature, body weight and a simple operant response for water reward. The flinders S-line were also more sensitive to the effects of DFP on locomotor activity, FR5 responding for a water reward, and analgesia, indicating some degree of generalization. However, diarrhea, a symptom of peripheral effects of DFP, occurred at a similar incidence in the two lines, although males of both lines had higher incidences than the females. Neither of the two lines was affected by DFP for variables in which aversive (i.e. shock) motivation was used: The number of discriminative escape responses and the escape times were similar. These findings indicate that while the effects of DFP do generalize beyond the criterion variables upon which selection was based, the generalization is relatively specific. The data are consistent with the hypothesis that the changes in sensitivity have arisen because of changes in the functioning of a central cholinergic system(s).