Effects of dopamine, norepinephrine and serotonin on secretion of luteinizing hormone, follicle-stimulating hormone and prolactin in ovariectomized, pituitary stalk-transected ewes

The incidence risk of breast and gynecological cancer by antidepressant use: A systematic review and dose–response meta-analysis of epidemiological studies involving 160,727 patients

Background and objective

Antidepressants are widely prescribed to treat depression and anxiety disorders that may become chronic conditions among women. Epidemiological studies have yielded inconsistent results on the correlation between antidepressant use and the incidence risk of female breast and gynecological cancer, along with uncertain dose–response relationship. Therefore, we performed a systematic review and dose–response meta-analysis to investigate the association.

Methods

Web of Science, Embase, PubMed, The Cochrane Library, and PsycINFO were systematically searched in January 2022, with no language limits. Random-effect models were used to calculate pooled effect sizes and 95% confidence intervals between studies. Linear and non-linear dose–response analyses were performed to evaluate the dose or duration of antidepressant use affecting the incidence risk of female breast and gynecological cancer. Further subgroup analyses were systematically performed by stratifying almost all study characteristics and important potential confounders, in order to further clarify and validate the important potential hypotheses regarding the biological mechanism underlying this association.

Results

Based on a systematic literature search, 34 eligible studies (27 case–control studies and 7 cohort studies) involving 160,727 female breast and gynecological cancer patients found that antidepressant use did not increase the incidence risk of female breast and gynecological cancer (pooled OR: 1.01; 95% CI: 0.97, 1.04, I² = 71.5%, p < 0.001), and even decreased the incidence risk of ovarian cancer (pooled OR: 0.91; 95% CI: 0.83, 1, I² = 17.4%, p = 0.293). There were a non-linear dose–response relationship (p non-linearity < 0.05) between the duration of antidepressant use and incidence risk of female breast cancer, and an inverse linear dose–response relationship between antidepressant use and the incidence risk of gynecological cancer, specifically with an increase of cumulative defined daily dose or duration to a high level, like 25,550 doses (OR: 0.91, 95% CI: 0.85–0.98, p linearity < 0.05) or 4,380 days (OR: 0.82; 95% CI: 0.7, 0.96, p linearity < 0.05), compared to never antidepressant users.

Conclusion

This systematic review and dose–response meta-analysis found that antidepressant use did not increase the incidence risk of female breast and gynecological cancer and even decreased the incidence risk of ovarian cancer, along with a non-linear or linear dose–response relationship.

Systematic Review Registration

PROSPERO https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=313364, identifier CRD42022313364.

Association between antidepressant medication use and epithelial ovarian cancer risk: a systematic review and meta-analysis of observational studies

AIM

The aim of this paper is to clarify the inconsistent findings in the association between antidepressant use and the risk of epithelial ovarian cancer (EOC).

METHODS

This study is a meta-analysis of observational studies retrieved from the PubMed, EMBASE, and Web of Science databases prior to August 15, 2017. Two researchers independently screened studies and extracted study characteristics and risk estimates. The odds ratios (OR) and 95% confidence intervals (CI) of EOC risk were summarized using an inverse variance weighted random-effects model. Heterogeneity between studies was assessed with the I² statistic.

RESULTS

Eight case-control studies involving 7878 EOC cases and 73 913 controls were identified. Compared with non-use, use of antidepressants was not significantly associated with EOC risk (summarized OR = 1.10, 95% CI: 0.91-1.32, I²  = 74.4%). Similar null results were also observed in the use of selective serotonin reuptake inhibitors (OR = 1.04, 95% CI = 0.80-1.35), tricyclic antidepressants (OR = 1.01, 95% CI = 0.79-1.30), and other antidepressant drugs (OR = 0.91, 95% CI = 0.74-1.12). Subgroup analyses of study characteristics, stratified by the type of control subjects, geographic location, exposure assessment, number of cases, and adjustment for potential confounders, showed that the ORs were broadly consistent across strata. The OR per 1 year-increment of duration was 0.99 (95% CI = 0.94-1.05, I²  = 40.0%, P = 0.154). Additionally, the OR for the greatest intensity of antidepressant use compared with never use was 0.82 (95% CI = 0.70-0.98, I²  = 0%, P = 0.489). Furthermore, no evidence of publication bias was detected through Funnel plots as well as Egger's and Begg's tests.

CONCLUSIONS

There is no association between antidepressant use and EOC risk. Further prospective studies are warranted to confirm these findings.

Effects of Prolactin on the Luteinizing Hormone Response to Gonadotropin-Releasing Hormone in Primary Pituitary Cell Cultures During the Ovine Annual Reproductive Cycle

In the sheep pituitary, the localization of prolactin (PRL) receptors in gonadotrophs and the existence of gonadotroph-lactotroph associations have provided morphological evidence for possible direct effects of PRL on gonadotropin secretion. Here, we investigated whether PRL can readily modify the LH response to GnRH throughout the ovine annual reproductive cycle. Cell populations were obtained from sheep pituitaries during the breeding season (BS) and the nonbreeding season (NBS), plated to monolayer cultures for 7 days, and assigned to receive one of the following treatments: 1) nil (control), 2) acute (90- min) bromocriptine (ABr), 3) chronic (7-day) bromocriptine (CBr), 4) ABr and PRL, 5) CBr and PRL, 6) PRL alone, or 7) thyrotropin-releasing hormone. Cells were treated as described above, with the aim of decreasing or increasing the concentrations of PRL in the culture, and simultaneously treated with GnRH for 90 min. The LH concentrations in the medium were then determined by RIA. GnRH stimulated LH in a dose-dependent manner during both stages of the annual reproductive cycle. During the NBS, single treatments did not significantly affect the LH response to GnRH. However, when PRL was combined with bromocriptine, either acutely or chronically, GnRH failed to stimulate LH release at all doses tested (P < 0.01). In contrast, during the BS, the LH response to GnRH was not affected by any of the experimental treatments. These results reveal no apparent effects of PRL alone, but an interaction between PRL and dopamine in the regulation of LH secretion within the pituitary gland, and a seasonal modulation of this mechanism.

Protein- and tryptophan-restricted diets induce changes in rat gonadal hormone levels

The release of gonadotrophic hormones starts at puberty and, along with the subsequent estral cyclicity, is subject to hormonal feedback systems and to the action of diverse neuroactive substances such as gamma amino butyric acid and catecholamines. This study shows the effect of the administration during 40 days of protein-restricted and corn-based (tryptophan- and lysine-deficient) diets on the serotonin concentration in medial hypothalamic fragments as well as in follicle-stimulating luteinizing hormones, 17-beta-estradiol and progesterone serum levels, and estral cyclicity in 60- and 100-day-old rats (young, mature, and in gestation). In young rats, a delay in vaginal aperture development, and a lengthening of the estral cycle to a continuous anestral state was observed, mainly in the group fed corn. This group showed a 25% decrease in the serotonin concentration compared with the protein-restricted group, which exhibited an increase of 9% over the control group. Luteinizing hormone levels decreased in 16% and 13%, whereas follicle-stimulating hormone increased in 13% and 5% in the young animals of restricted groups, respectively, compared with the control group. Serum progesterone levels decreased only in young restricted versus control animals, and no differences were seen among adult and gestational rats. Serum levels of 17-beta-estradiol in restricted animals showed different concentration patterns, mainly in the corn group, which was higher at the 20th gestational day, falling drastically postpartum. The results obtained in this study show serotonin to be a very important factor in the release of gonadotrophic hormones and the start of puberty.

Serotoninergic involvement in gonadotropin and TSH secretion in normal cycling and postmenopausal women

We investigated the influence of a specific serotonin receptor blockade on pituitary hormone secretion in normal cycling women and postmenopausal women not receiving hormone replacement therapy. Serotonin receptor blockade was performed by using the HT-3 receptor subtype antagonist ondansetron as an i.v. bolus injection of 8 mg. Blood samples were taken before as well as 20, 30 and 40 min after ondansetron administration for the estimation of LH, FSH, and TSH. We could not find any hormonal changes in the normal cycling women. The postmenopausal women showed a significant decline in LH secretion, whereas FSH and TSH levels remained unchanged. Our results suggest serotoninergic involvement in LH secretion in postmenopausal hypoestrogenic hypergonadism.

Interaction between hypothalamic dopaminergic and opioidergic systems in the photoperiodic regulation of pulsatile luteinizing hormone secretion in sheep

Previous studies in sheep have shown that whereas the inhibitory effects of dopamine (DA) systems on GnRH/gonadotrophin secretion are readily detectable during the sexually inactive phase under long days (LD), the suppressive effects of endogenous opioid peptide (EOP) systems are most evident during the sexually active phase under short days (SD). The hypothesis proposed in this study is that inhibitory DA pathways interact with EOP neurons to regulate GnRH/gonadotropin secretion in sheep and that photoperiod modulates this interaction to relay its effect on the seasonal reproductive cycle. To test this hypothesis, the effects of a DA agonist (bromocriptine) or of a DA antagonist (sulpiride) on the pulsatile LH response to an opioid antagonist (naloxone) were evaluated in sexually active Soay rams exposed to SD, and then reassessed when sexually inactive under LD. The experimental design comprised six treatments: 1) control (vehicle); 2) bromocriptine; 3) sulpiride; 4) naloxone; 5) pretreatment with bromocriptine followed by naloxone; 6) pretreatment with sulpiride followed by naloxone. Under SD, when DA pathways are thought to be quiescent and EOP systems active, bromocriptine suppressed pulsatile LH secretion (P < 0.01), whereas sulpiride had no effect. Under this photoperiod, naloxone induced a conspicuous stimulation of episodic LH release (P < 0.01). This effect was prevented by pretreatment with bromocriptine (P < 0.01), but was not affected by pretreatment with sulpiride. Conversely, under LD, when the activity of DA pathways is thought to be increased and that of EOP systems reduced, bromocriptine was without effect, whereas sulpiride evoked a mild increase in LH pulse frequency (P < 0.05). Under this photoperiod, naloxone induced a smaller stimulation than under SD. This effect was again blocked by pretreatment with bromocriptine but, in contrast to SD, markedly enhanced by pretreatment with sulpiride (P < 0.01). Particularly relevant was that the DA agonist blocked the stimulatory effects of the EOP antagonist under SD, and that the DA antagonist enhanced the effects of the EOP antagonist only under LD. These results are consistent with the hypothesis proposing that, in sheep, DA pathways have a predominant inhibitory effect on both GnRH and EOP neurons, and that changes in day length modulate the interplay between DA and EOP systems as part of the mechanisms involved in the photoperiodic control of the seasonal reproductive cycle.

Serotoninergic control of gonadotrophin and prolactin secretion in women

OBJECTIVE

Due to conflicting observations from previous investigations, the role of serotonin (5-HT) in the regulation of the human menstrual cycle has not been clearly established. We have therefore investigated the possible participation of 5-HR in the control of gonadotrophin and PRL secretion in women, using the potent 5-HT3 receptor antagonist ondansetron as a pharmacological probe.

DESIGN

Serum profiles of LH, FSH and PRL were obtained in 9 normally cycling women during a control and a treatment cycle, during which ondansetron (8 mg orally) was administered daily. On day 10 of both cycles, the serum pulsatility of LH, FSH and PRL was assessed by frequent blood sampling (at 10-minute intervals for 10 hours). Pituitary responsiveness was tested by administration of a GnRH bolus (25 micrograms i.v. after 8 hours).

MEASUREMENTS

LH, FSH and PRL were serially determined in all blood samples by immunofluorescence assays. The resulting hormone data arrays were searched for significant fluctuations by the Cluster pulse algorithm.

RESULTS

Compared with control cycles, the temporal organization and the endocrine characteristics of the treatment cycles remained virtually unaltered. Serotonin antagonism did not noticeably affect the LH pulse attributes (frequencies, interpulse intervals, amplitudes). Although FSH amplitudes declined markedly (P < 0.05), the remaining pulse attributes were unchanged. A clear increase (P < 0.05) in the PRL pulse frequency was noted, while PRL pulse amplitudes tended to increase (P = 0.1). Gonadotrophin and PRL release in response to GnRH administration was unaltered by ondansetron treatment.

CONCLUSIONS

Serotoninergic blockade by a selective 5-HT3 receptor antagonist failed to modify pulsatile LH secretion, but induced distinct changes in episodic FSH and PRL secretion. Since the pituitary gonadotrophin and PRL responsiveness remained unaltered during 5-HT3 receptor blockade, the observed alterations in the FSH and PRL secretion presumably relate to altered hypothalamic regulation of these pituitary hormones. Thus, the central regulation of pulsatile FSH and PRL release in women appears to involve 5-HT3 receptor-mediated processes.

Evidence that Dopaminergic Neurons are not Involved in the Negative Feedback Effect of Testosterone on Luteinizing Hormone in Rams in the Non-Breeding Season

In this study we tested the hypothesis that the negative feedback effects by testosterone on the secretion of luteinizing hormone (LH) in rams involves dopaminergic afferents to gonadotrophin-releasing hormone neurons operating via D(2) receptors in the non-breeding season. In the first experiment, three groups (n = 5) of rams were treated with an intravenous injection of vehicle or 10 or 20 mg of the dopaminergic D(2) antagonist pimozide and jugular venous samples were collected every 10 min for 3 h before and 3 h following treatment. The plasma was assayed for LH. Three groups of ewes (n = 4 to 5) were similarly treated. There were no significant effects of treatment of the rams with pimozide on the plasma concentrations of LH or LH pulse frequency or pulse amplitude and the response of individual rams in each group was inconsistent. In contrast, treatment of the ewes with 20 mg pimozide significantly (P<0.001) increased the mean (± SEM) plasma LH concentrations (pretreatment 0.37 ± 0.04; post-treatment 2.42±0.25 ng/ml) and decreased (P<0.001) the LH inter-pulse interval (pretreatment 180.0; post-treatment 88.0±11.1 min); the 10 mg dose of pimozide did not affect these parameters. In the second experiment, two groups of rams (n = 5) and ewes (n = 7) were treated with an intravenous injection of vehicle or 0.33 mg pimozide/kg liveweight and jugular venous samples were collected every 10 min for 2 h before and 6 h following treatment. As in the first experiment, the mean (± SEM) concentrations of plasma LH were not affected by treatment with pimozide in the rams (pretreatment 0.18 ± 0.25; post-treatment 0.43 ± 0.14 ng/ml) but were significantly (P<0.05) increased in the ewes (pretreatment 1.12±0.22; post-treatment 1.93 ± 0.23 ng/ml). In the third experiment, four adult rams were castrated and 3 weeks later each animal had two cannulae inserted to allow injection into the lateral cerebral ventricles. Vehicle or 100 μg pimozide was injected intracerebroventricularly and blood samples were collected as in the other experiments. A Latin Square design was used so that each animal received each treatment (n = 4). This procedure was repeated after the animals had been injected (intramuscularly) with 16 mg testosterone propionate twice daily for at least 7 days. Treatment with testosterone propionate significantly decreased (P < 0.001) the plasma concentrations of LH (pre-treatment 7.71±0.27; post-treatment 0.75 ± 0.27 ng/ml; mean ± SEM) and follicle-stimulating hormone (pre-treatment 79.61±8.47; post-treatment 42.53 ± 6.08 ng/ml; mean ± SEM) and increased the mean (± SEM) LH inter-pulse interval (53.14 ± 3.58 min pre-treatment and 292.5 ± 32.94 min post-treatment) but had no effect on the amplitude of LH pulses (pre-treatment 3.61 ± 0.36; post-treatment 1.86±1.76 ng; mean ± SEM). Pimozide had no effect on the plasma concentrations of gonadotrophins. These results suggest that, in the ram, dopaminergic neurons do not influence the gonadotrophin-releasing hormone neurons via D(2) receptors in the non-breeding season and are not involved in the negative feedback effect of testosterone on the secretion of gonadotrophins. Conversely, our data suggest that such a mechanism is integral to the negative feedback effects of oestradiol on LH in anoestrous ewes. Finally, it also appears that the steroid-independent suppression of the secretion of gonadotrophins during the non-breeding season in rams is not mediated via D(2) receptors.