Effects of short-term hyper- and hypoprolactinaemia on hormones of the pituitary, gonad and -thyroid axis and on semen quality in male Beagles

An Update on Male Canine Infertility

Infertility in the dog is a common reason for presentation of stud dogs for assessment with veterinarians. This article aims to discuss and outline some of the tests that can be done to try to ascertain the underlying cause of abnormalities found in a semen assessment. Topics discussed are semen alkaline phosphatase measurement, retrograde ejaculation assessment, ultrasound of the male reproductive tract, semen culture, human chorionic gonadotropin response testing, dietary assessment for phytoestrogens, environmental impacts on spermatogenesis, testicular biopsy, supplements to improve semen quality and quantity, and when to expect an improvement in semen quality after starting treatment.

Effects of whole-body vibration on reproductive physiology in a rat model of whole-body vibration

Findings from epidemiological studies suggest that occupational exposure to whole-body vibration (WBV) may increase the risk of miscarriage and contribute to a reduction in fertility rates in both men and women. However, workers exposed to WBV may also be exposed to other risk factors that contribute to reproductive dysfunction. The goal of this experiment was to examine the effects of WBV on reproductive physiology in a rat model. Male and female rats were exposed to WBV at the resonant frequency of the torso (31.5 Hz, 0.3 g amplitude) for 4 hr/day for 10 days. WBV exposure resulted in a significant reduction in number of developing follicles, and decrease in circulating estradiol concentrations, ovarian luteinizing hormone receptor protein levels, and marked changes in transcript levels for several factors involved in follicular development, cell cycle, and steroidogenesis. In males, WBV resulted in a significant reduction in spermatids and circulating prolactin levels, elevation in number of males having higher circulating testosterone concentrations, and marked alterations in levels of transcripts associated with oxidative stress, inflammation, and factors involved in regulating the cell cycle. Based upon these findings data indicate that occupational exposure to WBV contributes to adverse alterations in reproductive physiology in both genders that may lead to reduction in fertility.

Meningeal CGRP-Prolactin Interaction Evokes Female-Specific Migraine Behavior

OBJECTIVE

Migraine is three times more common in women. CGRP plays a critical role in migraine pathology and causes female-specific behavioral responses upon meningeal application. These effects are likely mediated through interactions of CGRP with signaling systems specific to females. Prolactin (PRL) levels have been correlated with migraine attacks. Here, we explore a potential interaction between CGRP and PRL in the meninges.

METHODS

Prolactin, CGRP, and receptor antagonists CGRP8-37 or Δ1-9-G129R-hPRL were administered onto the dura of rodents followed by behavioral testing. Immunohistochemistry was used to examine PRL, CGRP and Prolactin receptor (Prlr) expression within the dura. Electrophysiology on cultured and back-labeled trigeminal ganglia (TG) neurons was used to assess PRL-induced excitability. Finally, the effects of PRL on evoked CGRP release from ex vivo dura were measured.

RESULTS

We found that dural PRL produced sustained and long-lasting migraine-like behavior in cycling and ovariectomized female, but not male rodents. Prlr was expressed on dural afferent nerves in females with little-to-no presence in males. Consistent with this, PRL increased excitability only in female TG neurons innervating the dura and selectively sensitized CGRP release from female ex vivo dura. We demonstrate crosstalk between PRL and CGRP systems as CGRP8-37 decreases migraine-like responses to dural PRL. Reciprocally, Δ1-9-G129R-hPRL attenuates dural CGRP-induced migraine behaviors. Similarly, Prlr deletion from sensory neurons significantly reduced migraine-like responses to dural CGRP.

INTERPRETATION

This CGRP-PRL interaction in the meninges is a mechanism by which these peptides could produce female-selective responses and increase the prevalence of migraine in women. ANN NEUROL 2021;89:1129-1144.

Effects of Cabergoline on Thyroid Hormones and Semen Quality of Dog

In this study, the concentration of prolactin, FT4, and semen quality were investigated in 5 clinically healthy fertile mixed-breed dogs (1-3 years old) treated with cabergoline (5μg/kg) during 9 weeks. Semen analysis was performed for volume, live or dead, concentration, and motility factors every week. The results indicated that cabergoline administration caused a minor but significant reduction of the mean prolactin concentration (P < .05) and did not affect the secretion of FT4 (P > .05). Further, there was not a significant effect of cabergoline on semen quality, statistically. We could not find any relationship between prolactin and FT4 concentration and changes in semen characteristics.