Effects of injecting thymulin into the anterior or medial hypothalamus or the pituitary on induced ovulation in prepubertal mice.
In prepubertal mice, subcutaneous thymulin injection before equine chorionic gonadotrophin (eCG) treatment simulates ovulation; seemingly, the thymulin could be acting at the hypothalamus-pituitary axis level.


OBJECTIVE
This study was designed to analyze the effects of injecting thymulin into the hypothalamus or pituitary on induced ovulation of prepubertal mice.


METHODS
Female mice, 19 days old, were anesthetized with ether and injected with saline solution or thymulin into the anterior or medial hypothalamus or the pituitary and treated with eCG when 20 days old. The ova shed were counted and serum concentrations of 17beta-estradiol were measured. In the ovaries, the morphometrical analysis was performed and the atresia evaluated.


RESULTS
Ether anesthesia treatment blocked eCG-induced ovulation in almost all animals. Mice anesthetized and treated with eCG and gonadotrophin-releasing hormone (GnRH) or human chorionic gonadotrophin (hCG) ovulated a full quota of ova. Injecting saline solution into the anterior or medial hypothalamus or the pituitary did not reduce the blocking effects of ether anesthesia on induced ovulation, but the incidence of atretic follicles was higher. Injecting thymulin directly into the anterior hypothalamus did not restore ovulation, nor diminish the number of atretic follicles. In contrast, injecting thymulin into the medial hypothalamus restored the ovulation ratio and decreased the percentage of atretic follicles. Similar results were obtained by injecting thymulin into the pituitary, though thymulin treatment in the pituitary resulted in a higher number of ova shed and lower follicular atresia.


CONCLUSIONS
The present results suggest that thymulin acts at the medial hypothalamus level, facilitating the release of GnRH and at the pituitary level regulating gonadotrophin release.
García
Lorena
L
Biology of Reproduction Research Unit, Laboratory of Neuroimmuno-endocrinology, Facultad de Estudios Superiores Zaragoza, México, México.
Hinojosa
Lorena
L
Domínguez
Roberto
R
Chavira
Roberto
R
Rosas
Patricia
P
D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology; D007031:Hypothalamus / Q000187:drug effects* / Q000502:physiology; D007276:Injections, Intraventricular; D051379:Mice; D010053:Ovary / Q000187:drug effects; D010060:Ovulation / Q000187:drug effects*; D010902:Pituitary Gland / Q000187:drug effects* / Q000502:physiology; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000502:physiology; D012741:Sexual Maturation / Q000502:physiology*; D013935:Thymic Factor, Circulating / Q000008:administration & dosage* / Q000378:metabolism
D006063:Chorionic Gonadotropin; D007987:Gonadotropin-Releasing Hormone; D013935:Thymic Factor, Circulating