[Effect of photoperiodic conditions on the hypothalamo-hypophyseal neurosecretory and sexual system of the mink Mustela vison].

Cytomorphological analysis of the hypothalamo-hypophysial neurosecretory system (HHNS) and gonads has been made in minks under the following photoperiodic conditions: 1) control--natural light conditions; 2) natural light conditions in combination with artificial illumination to make total daylight up to 17 hours for 2 weeks in November; 3) Daylight reduced to 8 hours from July to October; 4) Combination of the 3rd and the 2nd regimes. Any change in photoperiodic conditions listed above results in activation of both the HHNS and gonads. Preliminary keeping the minks under the conditions of reduced daylight for 3 months significantly increases the reactivity of both systems to additional illumination in November. It is suggested that peptide neurohormones pass not only to total blood circulation in the region of the posterior pituitary, but also in the region of the median eminense, --i.e. in capillaries of the portal vessels of the adenohypophysis.