Testicular growth in American tree sparrows occurs in spring in response to increasing daylength. By early summer, male tree sparrows become unresponsive to long days (i.e., they become photorefractory), and their testes regress. This project explores the physiological mechanisms that turn seasonal breeding on and off. The first phase tests the hypotheses that (1) a thyroid hormone (T4) simulates longs days (and thyroidectomy, short days), and (2) for photorefractoriness to be induced, T4 must be available when male tree sparrows experience long days. The second phase examines the hypothesis that brain receptors for excitatory amino acids (e.g., L-glutamate) transmit processes photic information (from brain photoreceptors, the biological clock, and/or elsewhere) to neurons that control the secretion of reproductive hormones from the pituitary gland. The ultimate goal of the project is to strengthen and extend understanding of the physiological basis of seasonal reproduction.//

Agency
National Science Foundation (NSF)
Institute
Division of Integrative Organismal Systems (IOS)
Type
Standard Grant (Standard)
Application #
9104722
Program Officer
Vincent P. Gutschick
Project Start
Project End
Budget Start
1991-09-01
Budget End
1994-08-31
Support Year
Fiscal Year
1991
Total Cost
$138,000
Indirect Cost
Name
Kansas State University
Department
Type
DUNS #
City
Manhattan
State
KS
Country
United States
Zip Code
66506