Hydroxyindole-O-methyl transferase (HIOMT) and serotonin in the pineal gland of the vizcacha (Lagostomus maximus maximus).

Pineal glands of vizcachas collected from their natural habitat were studied. Hydroxyindole-O-methyl transferase (HIOMT) activity showed a great individual dispersion. However, the enzyme activity was significantly higher in males than in females. Serotonin was also assayed in the glands. It did not show significant differences between both sexes. The results are discussed in relation to the natural life conditions of this rodent.