Ultradian and Seasonal Rhythms in Plasma Gonadotropins, Prolactin, Cortisol, and Testosterone in Pinealectomized Rams*
- 1 February 1981
- journal article
- research article
- Published by The Endocrine Society in Endocrinology
- Vol. 108 (2) , 639-646
- https://doi.org/10.1210/endo-108-2-639
Abstract
Plasma concentrations of PRL, LH, cortisol, FSH, and testosterone were determined in pinealectomized (Px) and control rams at four times during a year. Basal levels of PRL decreased between spring and winter in controls from 44 ± 2 ng/ml (mean ± SE) to 16 ± 3 ng/ml, while in Px rams, a different biphasic pattern was observed (56 ± 9 ng/ml in the spring; 12 ± 3 ng/ml in the summer, 45 ± 8 ng/ml in the autumn, and 25 ± 5 ng/ml in the winter). There were no other significant seasonal differences or treatment effects in PRL episode frequency or peak height, nor did pinealectomy alter the ultradian rhythm. The control rams had a significant seasonal difference in LH peak frequency, being higher in summer than at any other time. The Px rams had no seasonal changes in this or any other parameter of LH secretion. There were no significant differences between Px and control rams in any aspect of cortisol secretion and no seasonal trends. No seasonal or treatment effects were observed in plasma testosterone levels. Plasma FSH tended to be highest in controls in autumn, but this peak was not observed in Px rams. These results indicate that the pineal gland of sheep is involved in some aspects of seasonal breeding, possibly synchronizing hormone secretion with environmental changes.Keywords
This publication has 13 references indexed in Scilit:
- A Statistical Method for Detection of Hormone Secretory SpikesJournal of Animal Science, 1978
- The effects of a sudden decrease or increase in daylength on prolactin secretion in the ramReproduction, 1978
- Serum Melatonin Concentrations During Different Stages of the Annual Reproductive Cycle in EwesBiology of Reproduction, 1978
- CHANGES IN CONCENTRATIONS OF FOLLICLE-STIMULATING HORMONE, LUTEINIZING HORMONE, PROLACTIN AND PROGESTERONE IN THE PLASMA OF EWES DURING THE TRANSITION FROM ANOESTRUS TO BREEDING ACTIVITYJournal of Endocrinology, 1977
- A Specific Radioimmunoassay for Melatonin in Biological Tissue and Fluids and its Validation by Gas Chromatography-Mass SpectrometryEndocrinology, 1977
- SEASONAL AND CIRCADIAN CHANGES IN THE EPISODIC RELEASE OF FOLLICLE-STIMULATING HORMONE, LUTEINIZING HORMONE AND TESTOSTERONE IN RAMS EXPOSED TO ARTIFICIAL PHOTOPERIODSJournal of Endocrinology, 1977
- Effect of Melatonin on the Reproductive Systems of Male and Female Syrian Hamsters: A Diurnal Rhythm in Sensitivity to Melatonin12Endocrinology, 1976
- Seasonal Profiles of Plasma Luteinizing Hormone, Testosterone and Estradiol in the RamEndocrinology, 1976
- SEASONAL VARIATION IN THE EPISODIC SECRETION OF LUTEINIZING HORMONE AND TESTOSTERONE IN THE RAMJournal of Endocrinology, 1976
- Studies on the breeding season and reproduction of the ewe Part I. The breeding season in different environments Part II. The breeding season in one localityThe Journal of Agricultural Science, 1952