Towards more physiological manipulations of hormones in field studies: Comparing the release dynamics of three kinds of testosterone implants, silastic tubing, time-release pellets and beeswax

Quispe, Rene; Trappschuh, Monika; Gahr, Manfred; Goymann, Wolfgang

doi:10.1016/j.ygcen.2015.01.007

Cited by 36 publications

(36 citation statements)

References 22 publications

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“…These concentrations were shown to be stable for up to 7 weeks in rabbits (Stratton et al ., ). Concentrations were still very high in house sparrows ( Passer domesticus ) 42 days after implantation (Turek et al ., ) and in Japanese quail these circulating concentrations were shown to be very stable for up to 6 weeks (Desjardins & Turek, ) although a more recent study in the same species identified peak concentrations on day 1 after implantation and a progressive decline during the 29 following days (Quispe et al ., ). Similarly, we observed here a fairly substantial and continuous decline of the plasma concentrations in testosterone–treated females after the peak observed on day 1.…”

Section: Discussionmentioning

confidence: 97%

Testosterone‐induced neuroendocrine changes in the medial preoptic area precede song activation and plasticity in song control nuclei of female canaries

Shevchouk

Ghorbanpoor

Ball

et al. 2017

Eur J of Neuroscience

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Testosterone plays a key role in the control of seasonal changes in singing behavior and its underlying neural circuitry. After administration of exogenous testosterone, song quality and song control nuclei volumes change over the course of weeks, but song rate increases within days. The medial preoptic nucleus (POM) controls sexual motivation and testosterone action in POM increases sexually motivated singing. In this study, we investigated the time course of testosterone action in the song control nuclei and POM, at the gross anatomical and cellular level. Photosensitive female canaries were injected with BrdU to label newborn neurons. One day later they were transferred to a long-day photoperiod and implanted with testosterone-filled or empty implants. Brains and blood were collected 1, 2, 9 or 21 days later. Testosterone increased POM volume within 1 day, whereas the volume of song control nuclei increased significantly only on day 21 even if a trend was already observed for HVC on day 9. The density of newborn neurons in HVC, labeled by Bromodeoxyuridine (BrdU) and doublecortin, was increased by testosterone on days 9 and 21 although a trend was already detectable on day 2. In POM, testosterone increased the number and size of aromatase-immunoreactive neurons already after 1 day. This rapid action of testosterone in POM supports its proposed role in controlling singing motivation. Although testosterone increased the number of newborn neurons in HVC rapidly (9, possibly 2 days), it is unlikely that these new neurons affect singing behavior before they mature and integrate into functional circuits.

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Section: Discussionmentioning

confidence: 97%

Testosterone‐induced neuroendocrine changes in the medial preoptic area precede song activation and plasticity in song control nuclei of female canaries

Shevchouk

Ghorbanpoor

Ball

et al. 2017

Eur J of Neuroscience

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“…Another important issue in the case of manipulations of mothers is the temporal pattern of hormone administration to a female. Specifically, there might be differences between single‐dose hormone administration (as in the case of injections) and a gradual release from implants (e.g., Bonier, Martin & Wingfield, ; Henriksen et al , ; for differences among types of implants see Quispe et al , ). However, we did not detect any effect of hormone delivery method.…”

Section: Discussionmentioning

confidence: 99%

Chicken or egg? Outcomes of experimental manipulations of maternally transmitted hormones depend on administration method – a meta‐analysis

2018

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Steroid hormones are important mediators of prenatal maternal effects in animals. Despite a growing number of studies involving experimental manipulation of these hormones, little is known about the impact of methodological differences among experiments on the final results expressed as offspring traits. Using a meta-analytical approach and a representative sample of experimental studies performed on birds, we tested the effect of two types of direct hormonal manipulations: manipulation of females (either by implantation of hormone pellets or injection of hormonal solutions) and manipulation of eggs by injection. In both types of manipulation we looked at the effects of two groups of hormones: corticosterone and androgens in the form of testosterone and androstenedione. We found that the average effect on offspring traits differed between the manipulation types, with a well-supported positive effect of egg manipulation and lack of a significant effect of maternal manipulation. The observed average positive effect for egg manipulation was driven mainly by androgen manipulations, while corticosterone manipulations exerted no overall effect, regardless of manipulation type. Detailed analyses revealed effects of varying size and direction depending on the specific offspring traits; e.g., egg manipulation positively affected physiology and behaviour (androgens), and negatively affected future reproduction (corticosterone). Effect size was negatively related to the dose of androgen injected into the eggs, but unrelated to timing of manipulation, offspring developmental stage at the time of measuring their traits, solvent type, the site of egg injection and maternal hormone delivery method. Despite the generally acknowledged importance of maternal hormones for offspring development in birds, the overall effect of their experimental elevation is rather weak, significantly heterogeneous and dependent on the hormone and type of manipulation. We conclude by providing general recommendations as to how hormonal manipulations should be performed in order to standardize their impact and the results achieved. We also emphasize the need for research on free-living birds with a focus on fitness-related and other long-term effects of maternal hormones.

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“…S3). Such an increase may be due to the following reasons: (i) TRPs are commercially available, and thus their use is a more standardized method (SIL are manually manufactured, and doses are likely subjected to higher variability within and between studies); (ii) TRPs provide a more controlled release of exogenous hormone compared with SIL (Fusani, 2008;Quispe et al, 2015), whose polymer membranes prevent Cort diffusion (Kincl et al, 1968) and force researchers to manually puncture holes in the tube or even cut the ends of it (thereby increasing variability among studies); (iii) TRPs have a pre-defined theoretical period of duration specified by the manufacturer, which may facilitate experimental design (but see our considerations above) and facilitate comparisons among studies; and (iv) TRPs are selfdegrading, avoiding the need to re-capture study subjects to remove implants at the end of the experiment (which may be difficult in the wild). However, tight research budgets might limit a wider use of TRP implants, as these are substantially more expensive than SIL.…”

Section: Discussionmentioning

confidence: 99%

Corticosterone implants make stress hyporesponsive birds

Torres-Medina

Cabezas

Marchant

et al. 2018

Journal of Experimental Biology

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In birds, the use of corticosterone (Cort) implants is a frequent tool aimed at simulating systemic elevations of this hormone and studying effects on biological traits (e.g. physiology, morphology, behavior). This manipulation may alter adrenocortical function, potentially changing both baseline (Cort) and stress-induced (Cort) plasma Cort levels. However, implant effects on the latter trait are rarely measured, disregarding downstream consequences of potentially altered stress responses. Here, we analyzed the effects of Cort implants on both Cort and Cort in nestling and adult European white storks, In addition, we performed a review of 50 studies using Cort implants in birds during the last two decades to contextualize stork results, assess researchers' patterns of use and infer current study biases. High and low doses of Cort implants resulted in a decrease of both Cort (31-71% below controls) and Cort (63-79% below controls) in storks. Our literature review revealed that Cort generally increases (72% of experiments) whereas Cort decreases (78% of experiments) following implant treatment in birds. Our results challenge and expand the prevailing assumption that Cort implants increase circulating Cort levels because: (i) Cort levels show a quadratic association with implant dose across bird species, and decreased levels may occur at both high and low implant doses, and (ii) Cort implants also decrease Cort levels, thus producing stress-hyporesponsive phenotypes. It is time to work towards a better understanding of the effects of Cort implants on adrenocortical function, before addressing downstream links to variation in other biological traits.

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Towards more physiological manipulations of hormones in field studies: Comparing the release dynamics of three kinds of testosterone implants, silastic tubing, time-release pellets and beeswax

Cited by 36 publications

References 22 publications

Testosterone‐induced neuroendocrine changes in the medial preoptic area precede song activation and plasticity in song control nuclei of female canaries

Testosterone‐induced neuroendocrine changes in the medial preoptic area precede song activation and plasticity in song control nuclei of female canaries

Chicken or egg? Outcomes of experimental manipulations of maternally transmitted hormones depend on administration method – a meta‐analysis

Corticosterone implants make stress hyporesponsive birds

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