A secondary surge of prolactin on the estrus afternoon

Szawka, Raphael E.; Anselmo-Franci, Janete Aparecida

doi:10.1016/j.lfs.2004.01.027

Cited by 12 publications

(20 citation statements)

References 56 publications

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“…In addition, except on pro‐oestrous afternoon, male and female rats responded similarly. Interestingly, during the secondary surge of prolactin on the afternoon of oestrous (28), though prolactin levels were already high, ether stress further increased them, resulting in the highest stress‐induced levels during the oestrous cycle.…”

Section: Discussionmentioning

confidence: 99%

Ovarian Steroids But Not the Locus Coeruleus Regulate Stress‐Induced Prolactin Secretion in Female Rats

Poletini

Szawka

Franci

et al. 2006

J Neuroendocrinology

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Stress has been proposed to stimulate prolactin release if its prestress levels are low, or to inhibit it if they are elevated, but the role of ovarian-steroid fluctuations in the prolactin stress response is not yet clearly understood. Because the noradrenergic nucleus locus coeruleus has been implicated in stress responses and generation of prolactin surges in female rats, the present study aimed to evaluate stress-induced prolactin secretion under different hormonal conditions, determining the effect of locus coeruleus lesion on each response. Blood samples were withdrawn from a jugular vein catheter 5 and 2 min before and 2, 5, 10, 15 and 30 min after ether stress in male rats, female rats during the oestrous cycle and ovariectomised rats treated with oil (OVX), oestradiol (OVE) or oestradiol plus progesterone (OVEP). Increased Fos immunoreactivity demonstrated locus coeruleus activation following ether stress. Ether stress increased both low (at 16.00 h in males, in OVX and on dioestrous and at 11.00 h on pro-oestrous and oestrous) and high plasma prolactin (at 16.00 h on oestrous and in OVE), but it decreased elevated prolactin levels during the afternoon on pro-oestrous and in OVEP. Locus coeruleus lesion prevented prolactin surges during the afternoon on pro-oestrous, oestrous, OVE and OVEP but did not modify either pattern (i.e. increase or decrease) or degree of prolactin stress response under any condition studied. The present data therefore suggest that oestradiol and progesterone modulate stress-induced prolactin secretion, regardless of its prestress levels. Moreover, the locus coeruleus is probably not involved in prolactin response to stress and most likely has a specific role in prolactin surges induced by ovarian steroids.

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Section: Discussionmentioning

confidence: 99%

Ovarian Steroids But Not the Locus Coeruleus Regulate Stress‐Induced Prolactin Secretion in Female Rats

Poletini

Szawka

Franci

et al. 2006

J Neuroendocrinology

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“…norepinephrine; PERIOD1; PERIOD2 IN FEMALE RATS, PROLACTIN (PRL) secretion has been proposed to result from synchronization among a circadian neural signal from the suprachiasmatic nucleus (SCN), both inhibitory and stimulatory neurotransmitter actions on the pituitary gland, and modulating effects of ovarian steroids (19). As a consequence of this synchronization, female rats display cyclical increases of PRL secretion characterized by two surges: the preovulatory surge of proestrous afternoon (64) and the secondary surge of estrous afternoon (12,70).The preovulatory surge of PRL depends on the levels of plasma ovarian steroids, because the increase of estradiol titers induces (45) and the increase of progesterone amplifies (76) this surge. Estradiol treatment in ovariectomized (OVX) rats induces daily PRL surges that occur at roughly the same time of day as the proestrous surge (13).…”

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confidence: 99%

Knockdown of clock genes in the suprachiasmatic nucleus blocks prolactin surges and alters FRA expression in the locus coeruleus of female rats

Poletini¹,

McKee²,

Kennett³

et al. 2007

American Journal of Physiology-Endocrinology and Metabolism

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Poletini MO, McKee DT, Kennett JE, Doster J, Freeman ME. Knockdown of clock genes in the suprachiasmatic nucleus blocks prolactin surges and alters FRA expression in the locus coeruleus of female rats. Am J Physiol Endocrinol Metab 293: E1325-E1334, 2007. First published August 28, 2007; doi:10.1152/ajpendo.00341.2007.-The nature of the circadian signal from the suprachiasmatic nucleus (SCN) required for prolactin (PRL) surges is unknown. Because the SCN neuronal circadian rhythm is determined by a feedback loop of Period (Per) 1, Per2, and circadian locomotor output cycles kaput (Clock) gene expressions, we investigated the effect of SCN rhythmicity on PRL surges by disrupting this loop. Because lesion of the locus coeruleus (LC) abolishes PRL surges and these neurons receive SCN projections, we investigated the role of SCN rhythmicity in the LC neuronal circadian rhythm as a possible component of the circadian mechanism regulating PRL surges. Cycling rats on proestrous day and estradiol-treated ovariectomized rats received injections of antisense or random-sequence deoxyoligonucleotide cocktails for clock genes (Per1, Per2, and Clock) in the SCN, and blood samples were taken for PRL measurements. The percentage of tyrosine hydroxylase-positive neurons immunoreactive to Fos-related antigen (FRA) was determined in ovariectomized rats submitted to the cocktail injections and in a 12:12-h light:dark (LD) or constant dark (DD) environment. The antisense cocktail abolished both the proestrous and the estradiolinduced PRL surges observed in the afternoon and the increase of FRA expression in the LC neurons at Zeitgeber time 14 in LD and at circadian time 14 in DD. Because SCN afferents and efferents were probably preserved, the SCN rhythmicity is essential for the magnitude of daily PRL surges in female rats as well as for LC neuronal circadian rhythm. SCN neurons therefore determine PRL secretory surges, possibly by modulating LC circadian neuronal activity. norepinephrine; PERIOD1; PERIOD2 IN FEMALE RATS, PROLACTIN (PRL) secretion has been proposed to result from synchronization among a circadian neural signal from the suprachiasmatic nucleus (SCN), both inhibitory and stimulatory neurotransmitter actions on the pituitary gland, and modulating effects of ovarian steroids (19). As a consequence of this synchronization, female rats display cyclical increases of PRL secretion characterized by two surges: the preovulatory surge of proestrous afternoon (64) and the secondary surge of estrous afternoon (12,70).The preovulatory surge of PRL depends on the levels of plasma ovarian steroids, because the increase of estradiol titers induces (45) and the increase of progesterone amplifies (76) this surge. Estradiol treatment in ovariectomized (OVX) rats induces daily PRL surges that occur at roughly the same time of day as the proestrous surge (13). Shifting of the light phase results in a coincident shift of the proestrous surge (10), and the estradiol-induced PRL surges of OVX rats free run in constant light (52), but the m...

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“…For these reasons, it has been considered that the afternoon of proestrus is the only time in which a major surge of PRL secretion occurs (Freeman et al 2000). Nonetheless, a secondary peak of PRL secretion during the afternoon of estrous has been described in cannulated female rats and related to the circulating levels of estradiol (Szawka & Anselmo-Franci 2004). Yet, the participation of other steroids during proestrus and estrus that may regulate PRL secretion during estrus has been scarcely studied.…”

Section: Discussionmentioning

confidence: 99%

“…In fact, preventing the effect of corticoids during proestrus with MIF or ORG evoked increase in serum PRL on estrus without modifications during proestrus. Szawka & Anselmo-Franci (2004) have concluded that the secondary peak of PRL occurring during estrus is estrogen-dependent. Accordingly, in our previous studies, we have shown that circulating adrenal corticoids clearly inhibited estrogen-induced PRL release (Caron et al 1994).…”

Section: Discussionmentioning

confidence: 99%

Regulation of prolactin secretion during the estrus in rats: possible role of glucocorticoids

López-Fontana¹,

Maselli²,

Nasso³

et al. 2011

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Mifepristone (MIF) administration to cycling rats at proestrus induces hypersecretion of prolactin (PRL) at the following estrus. We aimed to assess whether this effect is due to the antiprogesterone or antiglucocorticoid action of MIF and to help underscore the nature of the circulating hormone(s) regulating PRL secretion at estrus. Female cycling rats in proestrus were treated with vehicle; the progesterone (Pg) and glucocorticoid receptor antagonists, MIF (5 mg/kg) or ORG-33628 (5 mg/kg); the glucocorticoid agonist dexamethasone (DEX; 27 mg/kg)GMIF; or the inhibitor of steroid synthesis aminoglutethimide (AG; 150 mg/kg)GMIF. The animals' blood was sampled the same day at 1800 h and at 1800 h of the following day to assess for circulating PRL and Pg levels. To distinguish antiglucocorticoid from antiprogesterone effects of MIF, we administered a highly specific neutralizing antibody against Pg. None of the antagonists modified serum PRL values at proestrus but increased PRL levels at estrus. DEX decreased the secretion of PRL at proestrus, yet the effect was entirely blocked by MIF. Furthermore, DEX decreased PRL at estrus in a MIF-reversible manner, suggesting that adrenal corticoids during proestrous may regulate PRL secretion at estrus. AG increased PRL secretion at estrus, whereas its association with MIF produced an even higher response. PRL concentration at estrus was not modified by the antiprogesterone antibody, suggesting that the effect of MIF is a consequence of its antiglucocorticoid effect and not due to its antiprogesterone properties. In conclusion, PRL secretion in the afternoon of the estrus is most likely regulated by glucocorticoids through an inhibitory action.

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A secondary surge of prolactin on the estrus afternoon

Cited by 12 publications

References 56 publications

Ovarian Steroids But Not the Locus Coeruleus Regulate Stress‐Induced Prolactin Secretion in Female Rats

Ovarian Steroids But Not the Locus Coeruleus Regulate Stress‐Induced Prolactin Secretion in Female Rats

Knockdown of clock genes in the suprachiasmatic nucleus blocks prolactin surges and alters FRA expression in the locus coeruleus of female rats

Regulation of prolactin secretion during the estrus in rats: possible role of glucocorticoids

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