EFFECT OF DOMESTICATION ON THE BASIC ENZY MES OF SEROTONIN METABOLISMAND SEROTONIN RECEPTORS IN THE SILVER FOXES

In silver foxes significant alterations in the activities of basic enz ymes of neurotransmitter serotonin metabolism as well as in the densit ies of serotonin receptors caused by selection for the absence of the aggressive defensive reaction to man were demonstrated In the midbrain and hypothalamus of animals selected for the absence of aggressive be havior, the activity of tryptophan hydroxylase, the key enzyme of seto tonin biosynthesis, was found to be remarkably higher than in animals selected for highly aggressive behavior. Domesticated animals were cha racterized by low activity of the main enzyme of serotonin catabolism, monoamine oxydase type A, increased Michaeis costant (K-m), and an un changed maximum reaction rate (V-max). No changes in the specific bind ing of [H-3]-ketanserin and [H-3]-8-OH-DPAT in the frontal cortex of d omesticated foxes were revealed; however, in the hypothalamus, the low values of B-max for the [H-3]-8-OH-DPAT specific binding were observe d, indicating the decreased density of the 5-HT1A receptors. It is ass umed that the transformation of a wild aggressive animal into a domest icated one taking place during directional selection is caused by here ditary alterations favored by artificial selection In the activity of the main enzymes of serotonin metabolism and serotonin receptors.