IMPLANTATION OF OESTROGEN IN THE BRAIN AND THE INDUCTION OF OVULATION IN THE GUINEA-PIG

1974 ◽  
Vol 62 (1) ◽  
pp. 153-160 ◽  
Author(s):  
JANET E. BOOTH ◽  
B. T. DONOVAN
Keyword(s):  
Guinea Pig ◽  
Anterior Hypothalamus ◽  
Oestrous Cycle ◽  
Pars Distalis ◽  
Initial Exposure ◽  
Medial Basal Hypothalamus ◽  
Induction Of Ovulation ◽  
Gonadotrophin Secretion ◽  
Ovarian Activation ◽  
The Brain

SUMMARY In the guinea-pig, when bilateral oestrogen implants were placed in the medial basal hypothalamus, anterior hypothalamus or suprachiasmatic area on day 10 of the oestrous cycle, ovarian changes indicative of gonadotrophin secretion were observed on day 15. Similarly located cholesterol implants and oestrogen implants outside this region were without effect. The gonadotrophin release was likely to have been induced by an action of the steroid at the hypothalamic, rather than the pituitary level, since bilateral implants of oestrogen in the pars distalis caused ovarian activation in only one out of eight animals. Signs of normal ovulation were evident in only three out of 19 animals in which oestrogen was implanted in the medial basal hypothalamus on day 10 and left in place for 10 days. The ovaries of some other animals bore the traces of luteal bodies formed in response to the initial exposure to oestrogen; other ovaries contained only large healthy or atretic follicles and spontaneous ovulation was apparently blocked. It is concluded that exposure of the hypothalamo-hypophysial system of the guinea-pig to an increased amount of oestrogen initially stimulates and then inhibits ovulatory gonadotrophin secretion. Tonic gonadotrophin secretion is unaffected.

INDUCTION OF OVULATION IN SHEEP BY ELECTRICAL STIMULATION OF HYPOTHALAMIC REGIONS

1970 ◽  
Vol 46 (3) ◽  
pp. 305-311 ◽  
Author(s):  
F. PRZEKOP ◽  
E. DOMAŃSKI
Keyword(s):  
Electrical Stimulation ◽  
Breeding Season ◽  
Anterior Hypothalamus ◽  
Oestrous Cycle ◽  
Induction Of Ovulation ◽  
Gonadotrophin Secretion ◽  
Hypothalamic Nuclei ◽  
Medial Hypothalamus ◽  
Stimulation Of

SUMMARY Electrical stimulation of the anterior hypothalamus (regions of the supraoptic and anterior hypothalamic nuclei) or of the ventro-medial hypothalamus (infundibular or ventro-medial nuclei) during the last month of anoestrus in ewes induced ovulation within 72 hr., while similar stimulation of the same centres during the breeding season on the 12th day of the oestrous cycle did not advance ovulation. The role of the hypothalamic centres in the control of gonadotrophin secretion and ovulation is discussed in the light of these results.

THE HORMONAL INDUCTION OF OVULATION OR OF LUTEINIZATION IN THE INTACT OR HYPOPHYSECTOMIZED GUINEA-PIG

1974 ◽  
Vol 60 (2) ◽  
pp. 285-292 ◽  
Author(s):  
B. T. DONOVAN ◽  
A. N. LOCKHART
Keyword(s):  
Guinea Pig ◽  
Combined Treatment ◽  
Hormone Treatment ◽  
Ovarian Follicles ◽  
Oestrous Cycle ◽  
Induction Of Ovulation ◽  
Hormonal Induction

SUMMARY The induction of ovulation and follicular luteinization in the guinea-pig by follicle-stimulating (FSH) and luteinizing (LH) hormones was studied in the intact and in the hypophysectomized animal. Follicular luteinization could be produced as early as day 8 of the oestrous cycle by 250 mu. FSH, but not before day 10 by 400 mu. LH, while either FSH or LH caused ovulation when given on day 12 or later. When injected on day 13, luteinization could be induced with 62·5 mu. FSH or 200 mu. LH. Luteinization of follicles also occurred when 400 mu. LH or 250 mu. FSH was given immediately after hypophysectomy on day 13, but when hormone treatment was delayed for 4·5 h after surgery the incidence of luteinization was greatly reduced. Combined treatment with 200 mu. LH and 125 mu. FSH, by contrast, readily caused luteinization. It is concluded that ovarian follicles are resistant to luteinization during the first half of the oestrous cycle and that the response to LH late in the cycle is dependent upon the maintenance of follicular responsiveness by endogenous gonadotrophin.

THE MECHANISM OF THE INDUCTION OF OVULATION BY OESTROGENS

1965 ◽  
Vol 33 (3) ◽  
pp. 491-499 ◽  
Author(s):  
F. DÖCKE ◽  
G. DÖRNER
Keyword(s):  
Effective Dose ◽  
Corpus Luteum ◽  
Anterior Pituitary ◽  
Anterior Hypothalamus ◽  
Female Rats ◽  
Main Site ◽  
Induction Of Ovulation ◽  
Gonadotrophin Secretion ◽  
Oestradiol Benzoate ◽  
Electrolytic Lesions

SUMMARY To study the positive feed-back mechanism by which oestrogen induces corpus luteum formation, electrolytic lesions were placed in different parts of the anterior hypothalamus of prepubertal female rats which were then injected with oestradiol benzoate. Ovarian luteinization did not occur when the main parts of the suprachiasmatic nuclei or of the medial preoptic area had been destroyed. Oestradiol benzoate was implanted stereotaxically into the brain and the anterior pituitary of immature female rats. Whereas 1/25 of the subcutaneously effective dose had to be implanted into the anterior hypothalamus, 1/100 of the peripherally effective dose introduced into the adenohypophysis was sufficient to induce corpus luteum formation in most of the treated animals. The results suggest that, although the anterior hypothalamus is necessary for this positive feed-back mechanism, the anterior pituitary may be the main site of action of oestrogen. Oestrogen may increase the hypophysial sensitivity to the hypothalamic gonadotrophin-releasing factor. Thus an enhanced gonadotrophin secretion may result, sufficient for the induction of ovulation. The possibility is discussed that this positive feed-back mechanism is also essential for the induction of ovulation in women.

HYPOTHALAMIC SEXUAL PRECOCITY IN FEMALE RATS OPERATED SHORTLY AFTER BIRTH

1962 ◽  
Vol 41 (2) ◽  
pp. 301-313 ◽  
Author(s):  
S. Horowitz ◽  
J. J. Van der Werff ten Bosch
Keyword(s):  
Anterior Commissure ◽  
Anterior Hypothalamus ◽  
Female Rats ◽  
Vaginal Opening ◽  
Sexual Precocity ◽  
Paraventricular Nuclei ◽  
Gonadotrophin Secretion ◽  
Electrolytic Lesions

ABSTRACT Electrolytic lesions were placed in the anterior hypothalamus of 3–4 day-old female rats; vaginal opening was hastened in comparison with blank-operated littermates in 12 of 17 rats bearing a lesion in the basal supra-and post-chiasmatic area. In the animals with the earliest vaginal opening, lesions reached upward towards the region of the anterior commissure and the paraventricular nuclei. The degree of advancement of puberty in rats operated at the age of 3 or 4 days was similar to that caused by lesions made at 10, 14 or 15 days. This finding suggests that the effect of a lesion upon gonadotrophin secretion does not begin to take place until after the age of at least two weeks.

ADRENERGIC INPUTS TO THE AMYGDALA AND THE CONTROL OF GONADOTROPHIN RELEASE

1979 ◽  
Vol 90 (3) ◽  
pp. 385-393 ◽  
Author(s):  
José Borrell ◽  
Flavio Piva ◽  
Luciano Martini
Keyword(s):  
Brain Stem ◽  
Dopamine Receptor ◽  
Serum Levels ◽  
Female Rats ◽  
Receptor Blocker ◽  
Dopaminergic Drug ◽  
Gonadotrophin Secretion ◽  
Biphasic Effect ◽  
Adrenergic Blocker ◽  
The Brain

ABSTRACT Drugs able to mimic or to antagonize the action of catecholamines have been implanted bilaterally into the basomedial region of the amygdala of adult castrated female rats. The animals were killed at different intervals after the implantation of the different drugs, and serum levels of LH and FSH were measured by radioimmunoassay. The results have shown that the intra-amygdalar implantation of the alpha-adrenergic blocker phenoxybenzamine induces a significant increase of the release both of LH and FSH. The implantation of the beta-adrenergic blocker propranolol brings about a rise of LH only. The dopamine receptor blocker pimozide stimulates the release of LH and exerts a biphasic effect (stimulation followed by inhibition) of FSH secretion. The alpha-receptor stimulant clonidine and the dopaminergic drug 2-Br-alpha-ergocryptine were without significant effects. From these observations it is suggested that the adrenergic signals reaching the basomedial area of the amygdala (possibly from the brain stem) may be involved in the modulation of gonadotrophin secretion.

Phase-Locked Responses to Pure Tones in the Inferior Colliculus

2006 ◽  
Vol 95 (3) ◽  
pp. 1926-1935 ◽  
Author(s):  
Liang-Fa Liu ◽  
Alan R. Palmer ◽  
Mark N. Wallace
Keyword(s):  
Guinea Pig ◽  
Inferior Colliculus ◽  
Phase Locking ◽  
Single Units ◽  
Central Nucleus ◽  
Dorsal Cortex ◽  
Upper Limits ◽  
Ascending Pathways ◽  
Pure Tones ◽  
The Brain

In the auditory system, some ascending pathways preserve the precise timing information present in a temporal code of frequency. This can be measured by studying responses that are phase-locked to the stimulus waveform. At each stage along a pathway, there is a reduction in the upper frequency limit of the phase-locking and an increase in the steady-state latency. In the guinea pig, phase-locked responses to pure tones have been described at various levels from auditory nerve to neocortex but not in the inferior colliculus (IC). Therefore we made recordings from 161 single units in guinea pig IC. Of these single units, 68% (110/161) showed phase-locked responses. Cells that phase-locked were mainly located in the central nucleus but also occurred in the dorsal cortex and external nucleus. The upper limiting frequency of phase-locking varied greatly between units (80−1,034 Hz) and between anatomical divisions. The upper limits in the three divisions were central nucleus, >1,000 Hz; dorsal cortex, 700 Hz; external nucleus, 320 Hz. The mean latencies also varied and were central nucleus, 8.2 ± 2.8 (SD) ms; dorsal cortex, 17.2 ms; external nucleus, 13.3 ms. We conclude that many cells in the central nucleus receive direct inputs from the brain stem, whereas cells in the external and dorsal divisions receive input from other structures that may include the forebrain.

PRODUCTION OF PROSTAGLANDINS BY THE GUINEA-PIG UTERUS

1972 ◽  
Vol 54 (1) ◽  
pp. 147-159 ◽  
Author(s):  
N. L. POYSER
Keyword(s):  
Guinea Pig ◽  
Guinea Pigs ◽  
Oestrous Cycle ◽  
Prostaglandin E ◽  
Prostaglandin F

SUMMARY The production of prostaglandins by the uterus and the resting levels of prostaglandins in the uterus on selected days of the oestrous cycle were determined in guinea-pigs. Prostaglandin F2α was detectable in the guinea-pig uterus in small amounts on days 13, 14 and 15 of the cycle. Prostaglandin E2 was present in even smaller amounts on days 14 and 15. The homogenized guinea-pig uterus had the ability to biosynthesize prostaglandins, from endogenous precursors, during incubation on every day of the cycle studied. Four to six times more prostaglandin F2α than E2 was produced on any one day with the amounts of prostaglandins formed increasing towards the end of the oestrous cycle. Indomethacin inhibited the biosynthesis of prostaglandins by the guinea-pig uterus. The implications of these findings are discussed.

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