Biochemistry of nervous dogs

Previous behavioral studies on a nervous strain of pointer dogs have demonstrated genetic as well as environmental components in the nervous trait. Behaviorally these animals are extremely hypervigilant, with an apparent low threshold to fear and show strong avoidance of humans. In addition, the nervous E strain dogs show an unusually high degree of sensitivity to the mange mite. These observations led to the initiation of studies to determine whether differences exist between the normal A strain and the E strain of dogs at the biochemical level. Although a number of biochemical parameters examined have shown no statistically significant difference between the two strains, the modification of serum creatine phosphokinase (CPK) activity in response to various types of stress does differ as a function of strain—the nervous dogs being less, not more, responsive than the healthy dogs. When not specifically subjected to stress the serum CPK levels in both strains were highly related to age. Significant differences between strains also have been demonstrated in the cerebrospinal fluid acetyl cholinesterase activity levels in older animals. Tryptophan loading experiments, conducted in the presence and absence of the monoamine oxidase inhibitor, tranylcypromine, resulted in no readily observable behavioral modification of either strain and the response of the cerebrospinal fluid 5-hydroxyindoleacetic acid levels was similar for the two strains.