No indications of socially induced changes in brain aromatase activity in guppy (Poecilia reticulata) males

Sammanfattning: Aromatase is the enzyme that catalysis the conversion of androgens into estrogens. It´s a member of P450 cytochrome family and is encoded by the CYP19-gene. The enzyme aromatase has an important role in regulating physiological and behavioral sexual mechanisms. This includes for instance activation, motivation and maintenance of the reproductive behaviors. The sexual behavior is affected by a complex series of events that requires the connection of endogenous hormonal and neurochemical changes with social interactions, especially between the opposite sexes. The aim of the present study was to examine how social interactions effect the aromatase expression and activity in the guppy brain. Guppy males were introduced into four different social conditions: Isolated, all male conditions, heterospecific (with zebrafish females) and conspecific female guppies. The focal males were kept under these conditions for two respectively four days. The sexual behavior, of each of the focal males was recorded daily during 10 minutes. The males with the guppy females showed, in contrast to the males in the other groups, a high frequency of reproductive behaviors. The brains of the focal males were collected and the brain aromatase activity was measured using tritiated water assay. I have also tried to analyze the gene-expression of aromatase with RT-PCR. However I was unable to analyze the results with the RT-PCR, because of possible primer-dimerization. Due to the limited time schedule, we were not able to solve the problem. ANOVA performed on the aromatase activity, revealed no significant difference between the different treatment groups. The variance was highest in the zebrafish category and lowest in the isolated males. There was no significant correlation between the mean number of reproductive behaviors and the aromatase activity in males that were together with guppy females. The results do not support the hypothesis that social interactions can affect the brain aromatase activity in guppy males.