EFFECT OF PROLONGED DAILY PHOTOPERIODS ON THE HYPOTHALAMIC NEUROSECRETORY SYSTEM OF THE TREE SPARROW (PASSER MONTANUS SATURATUS)

• Published in: Endocrinologia Japonica Vol. 13; no. 1; pp. 23 - 38
• Main Author: MATSUI, Tokuzo
• Format: Journal Article
• Language: English
• Published: Japan The Japan Endocrine Society 1966
• Subjects: Animals; Axons - anatomy & histology; Birds; Body Weight; Dehydration; Female; Gonads; Hypothalamo-Hypophyseal System; Hypothalamus - physiology; Light; Male; Neurosecretion - physiology; Organ Size; Pituitary Gland, Posterior - anatomy & histology
• ISSN: 0013-7219; 2185-6370
• DOI: 10.1507/endocrj1954.13.23

The tree sparrow, Passer montanus saturatus, was exposed to prolonged daily photoperiods (20L 4D). The body weight decreased significantly on the 14th day of the treatment and thereafter began to increase gradually toward the initial weight up to the 37th day. Gonadal growth in both sexes was marked after exposure to long days. Neurosecretory material in the median eminence tended to decrease on the 14th and 24th days, but increased to the control level by the 37th day. Four neurosecretory cell groups, the medial supraoptic group (Sm), the intermediate supraoptic group (Si), the anterior paraventricular group (Pa) and the lateral paraventricular group (P1), were strongly stimulated by long days. The nuclear size of the cells of Si and Sm, reached its maximum on the 24th day and was maintained until the end of the experiment (37th day). The cell nuclei of Pa and Pl showed the maximal size on the 14th day. Thereafter, those of Pa maintained their maximal nuclear size up to the 37th day, while those of Pl showed a gradual decrease in size to those of control birds by the 37th day of the experiment. Two neurosecretory cell groups, the lateral supraoptic group (Sl) and the antero-medial paraventricular group (Pam), were stimulated significantly. The maximum nuclear size of the cells of Sl and Pam was reached on the 14th day. Thereafter, the cells showed a gradual decrease in size to those of controls by the 37th day. Cells of the three groups, the postero-medial paraventricular group (Ppm), the entopeduncular group (E) and the occipito-mesencephalic tract group (Om), did not respond in nuclear size to long days. Functional differences among different neurosecretory cell groups and possible axonal links between the nine neurosecretory cell groups and two neurosecretory terminal components, the median eminence and the pars nervosa, are briefly discussed.