Direct effect of prolactin, induced by TRH injection, on ovarian oestradiol secretion in the ewe

McNeilly, Alan S.; Baird, D. T.

doi:10.1530/jrf.0.0690559

Cited by 29 publications

(18 citation statements)

References 23 publications

(23 reference statements)

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“…Intracerebroventricular injection of 13-endorphin increases prolactin release in the ewe, while on the contrary immunoneutralization of the opiate pep tide lowers it [23,24], As demonstrated earlier [25], increases in prolactin secretion in anestrous ewes during infusion of melatonin is accompanied by a parallel rise in plasma (3-endorphin concentration. Opiate peptides stimulate prolactin release by decreasing the activity of tuberoinfundibular DA neurons [26,27], Plasma [3-endorphin largely derives from the pituitary gland [28] and does not cross the blood-brain barrier, but an increase in P-endorphin release in the arcuate nucleus may result from melatonin infusion [25] and thus affect the median eminence [29], TRH could also be involved, since administration of the tripeptide also increases plasma levels of prolactin in the ewe [30,31 ]. In contrast, active immunization against TRH does not prevent prolactin changes observed during the estrous cycle, pregnancy or lactation [32], Neverthe less, amounts of prolactin released under these conditions are lower than in control ewes.…”

Section: Discussionmentioning

confidence: 99%

Natural and Melatonin-Stimulated Changes in the Circadian Rhythm of Prolactin Secretion in the Ewe during Seasonal Anestrus

Misztal

Romanowicz

Barcikowski³

1997

Neuroendocrinology

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The relations between the circadian rhythms of melatonin and prolactin, and the effect of melatonin infused into the third ventricle or the mediobasal hypo-thalamus (MBH) on prolactin secretion and dopamine (DA) release were studied in anestrous ewes under increasing daylength conditions. The decreased amplitude and duration of nocturnal melatonin secretion were accompanied with changes in the daily pattern of prolactin secretion. Marked peaks of prolactin occurred after sunrise and melatonin decreases in February, as well as significant evening or nocturnal peaks under long day conditions between April and July. Melatonin infused into the third ventricle evoked an abrupt increase in the concentration of prolactin after 30 min, and the enhanced prolactin level was significantly higher than during the control infusion (range from 204 ± 75 to 248 ± 48 ng/ml vs. 128 ± 68 to 149 ± 93 ng/ml, mean ± SD). The concentrations of DA in MBH perfusates decreased during perfusion of melatonin but to a degree similar to that noted in untreated ewes. These data suggest that short-term infusions of melatonin stimulate the secretion of prolactin in the ewe under increasing daylength conditions, and that this effect is not mediated by changes in DA release.

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Section: Discussionmentioning

confidence: 99%

Natural and Melatonin-Stimulated Changes in the Circadian Rhythm of Prolactin Secretion in the Ewe during Seasonal Anestrus

Misztal

Romanowicz

Barcikowski³

1997

Neuroendocrinology

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“…Contradictory evidence has been reported (Chamley, 1978;Forrest, Fleeger, Long, Sorensen & Harms, 1980;Wright, Findlay & Anderson, 1981;McNeilly & Baird, 1983). Administration of prolactin from weaning through first oestrus did not produce a change in the LH pattern (Dusza et al, 1984).…”

Section: Discussionmentioning

confidence: 99%

Prolactin administration during the luteal and follicular phase of the oestrous cycle of gilts

Dusza¹,

Tilton²,

Weigl³

1986

Reproduction

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Summary. In Exp. I infusions of prolactin (0\m=.\5mg in 2 ml sterile saline) were repeated every 2 h for 36 h on Days 12\p=n-\13of the cycle. In Exp. II infusions of prolactin were administered from Days 17 to 19 (60 h) at 2-h intervals. Control gilts were given 2 ml sterile saline at similar intervals during the same period. Basal prolactin concentrations before initiation of infusions ranged from 1\m=.\3\ m=+-\0\m=.\1to 5\m=.\6\ m=+-\ 2\m=.\2 ng/ml in both experiments. By 5 min after a prolactin infusion, mean plasma prolactin concentration ranged from 74\m=.\9\ m=+-\5\m=.\8to 113\m=.\0\ m=+-\ 9\m=.\5ng/ml, but then declined to \ m=si meq\ 10 ng/ml just before the next infusion of prolactin. Administration of prolactin during the luteal phase of the oestrous cycle of the gilts had no effect on basal levels of progesterone, oestradiol or LH. During the follicular phase there were no differences (P >0\m=.\05) between control and prolactin-treated gilt progesterone and LH concentrations, but oestradiol plasma values were decreased (P <0\m=.\05) on the 2nd and 3rd day of prolactin treatment. Our results would indicate that prolactin does not play a major role in the regulation of the oestrous cycle of the pig.

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“…The possibility also exists that this drug blocks the action of dopamine on prolactin release at the pituitary level 16-18 . McNeilly et al (1982) 19 has been reported that prolactin is involved directly in the normal regulation of ovarian function; the precise mechanisms remain to be discovered. There is also clear evidence that in some species abnormally elevated prolactin levels in physiological situations are associated with the inhibition of normal ovarian activity by an action directly on the ovary.…”

Section: Discussionmentioning

confidence: 99%

Effects of chlorpromazine on the onset of puberty and follicular development in immature female rats

Ali

Bhagya

2011

Toxicol. Environ. Health Sci.

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Effect of chlorpromazine (dopamine receptor antagonist) on pre-pubertal ovarian follicular development and onset of puberty were studied. Fifteen days old female rats were administered chlorpromazine (2.5 mg /kg body weight) daily for 21 days and appropriate controls were maintained. The onset of puberty in immature female rats was delayed following chlorpromazine treatment. There were significant increases in the body weight, ovary weight and diameter of the ovary of controls and treated group over the initial controls. Ovary of the initial controls consisted of primordial (type 2), primary (type 3a, 3b), pre-antral (type 4, 5a, 5b) and antral (type 6) follicles whereas, antral (type 7) and pre-ovulatory follicles (type 8) were not developed. Controls and treated group consisted of all types of follicles i.e. primordial to pre-ovulatory follicles. Primordial follicles were reduced in number significantly in the ovary of the controls and treated group when compared with the initial controls whereas there was no significant variation among the controls and the treated group. The mean number of primary, pre-antral and antral (type 6) follicles in the control and treated group increased significantly over the initial controls. However, there was a significant reduction in the mean number of these follicles in the treated group when compared to controls. The mean number of type 7 (antral) and type 8 (pre-ovulatory) follicles were reduced in the treated group when compared with controls. The number of atretic follicles of the primary, pre-antral and antral (type 6) follicles significantly increased in controls and treated group over the initial controls. When compared to controls the mean number of atretic follicles belonging to primary, pre-antral, antral (type 6 and 7) and pre-ovulatory category were significantly higher in treated group and the number of corpora lutea was significantly lower. The results indicate that chlorpromazine effect results in loss of follicles by atresia and delay the onset of puberty in immature female rats.

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Direct effect of prolactin, induced by TRH injection, on ovarian oestradiol secretion in the ewe

Abstract: Summary. The These results show that TRH treatment, presumably by maintaining elevated plasma levels of prolactin, results in suppression of oestradiol secretion by a direct effect on the ovary in the ewe.

Cited by 29 publications

References 23 publications

Natural and Melatonin-Stimulated Changes in the Circadian Rhythm of Prolactin Secretion in the Ewe during Seasonal Anestrus

Natural and Melatonin-Stimulated Changes in the Circadian Rhythm of Prolactin Secretion in the Ewe during Seasonal Anestrus

Prolactin administration during the luteal and follicular phase of the oestrous cycle of gilts

Effects of chlorpromazine on the onset of puberty and follicular development in immature female rats

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