- Hormones, Brain and Behavior
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Hormones, Brain and Behavior
Please review our Terms and Conditions of Use and check box below to share full-text version of article. Abstract Thyroid hormones THs , T3 and T4, have many physiological actions and are essential for normal behavioral, intellectual and neurological development.
Figure 1 Open in figure viewer PowerPoint. Clinical observations THs are essential for brain maturation from early stages of development. Models of maternal hypothyroidism and hypothyroxinemia In the rat, THs are mainly required for proper brain maturation from the late fetal E14 to early postnatal stages 3—4 weeks affecting the maturation of neuronal structures such as the cerebral cortex, basal forebrain, cerebellum and hippocampus Bernal Akaike, M.
Neurotoxicol Teratol 13 , — Citing Literature. Volume 6 , Issue s1 June Pages Figures References Related Information. Close Figure Viewer. Browse All Figures Return to Figure. Previous Figure Next Figure.
Email or Customer ID. Forgot password? Old Password. New Password. Prenatal T treatment of female guinea pigs resulted in male typical behavior in adulthood, but the effect was not observed when T treatment was performed on females either perinatally or in adulthood [ 5 ]. This suggests that the brain is organized towards masculinization or feminization during the embryonic or fetal periods and that the gonadal hormones activate neural tissues for expression of male or female typical behavior in adult animals [ 5 ].
However, the presence of critical periods for gonadal hormone action in organizing or programing the nervous system remains controversial as it has been shown that sexual dimorphism of the brain can be repatterned postnatally [ 8 ]. As E2 is known to masculinize the female brain [ 9 ], T was assumed to be converted to E2 by aromatase to regulate brain patterning.
Subsequent studies have shown that E2 is involved in induction of cyclooxygenase 2, a key enzyme in prostaglandin E 2 PGE 2 synthesis which has been suggested to regulate sexual behavior in mice [ 10 ].
Hormones, Brain and Behavior - 1st Edition
Gonadal hormones and prostaglandins can modulate the central nervous systems of birds and mammals, altering sexual behavior. However, there is insufficient data on teleosts to link hormonal roles to neural circuit organization and sexual behavior. Teleosts demonstrate a remarkable ability to undergo sex reversal both by hormonal treatment and socially controlled cues [ 11 ]. Bluebanded gobies live in groups consisting of a dominant male with several females and show sex reversal in both directions. Removal of the male from the group triggers the largest female within the group to undergo gonadal, morphological, and behavioral changes to become a fertile male.
During this transition, aromatase activity drops quicker in the brain than in the gonads [ 11 ]. Fadrazole, an inhibitor of aromatase, and ketotestosterone KT treatment of the blackeye goby resulted in protogynous sex change [ 12 ]. The gonadotropin releasing hormone GnRH neuron numbers in the preoptic area of the hypothalamus is higher in male bluehead wrasses and KT treatment increases GnRH neurons and sex change in females [ 13 ].
When placed with a receptive female KT treated female goldfish showed male typical behavior while T exposure resulted in low level of masculinization [ 14 ]. MT treatment has also been shown to induce male typical behavior in female goldfish [ 15 ] and in female three-spined stickleback [ 16 ].
This suggests that in teleost KT induces male typical behavior in females and that E2 has feminizing properties. Apart from gonadal hormones, prostaglandin is also known to regulate sex differentiation and sexual behavior in teleosts. Inhibition of PGE 2 synthesis by meloxicam, a non-steroidal anti-inflammatory drug NSAID , resulted in an increased male to female sex ratio in zebrafish [ 20 ]. Taken together this suggests that prostaglandins can have a significant effect on teleost gonadal and brain functions.
While hormone [ 24 , 25 ] and prostaglandin [ 20 ] treatment of zebrafish has been shown to result in sex reversal less is known about the role of gonadal hormones in brain organization and activation of sexual behavior. However, transcriptomic studies have shown that the zebrafish brain is sexually dimorphic [ 26 — 28 ]. To explore the activation of sexual behavior zebrafish were exposed to sex steroids and prostaglandins.
Since gonadal hormones and prostaglandins can cause sex reversal in zebrafish, the exposure was performed on adult fish to determine if sexual behavior could be altered during the active reproductive stage. Wild type zebrafish were obtained from a local pet store in Sweden. Due to the short half-life of prostaglandins, water was completely changed each day. The brains were then removed and dissected into three regions: 1 forebrain containing olfactory bulb and telencephalon; 2 midbrain containing tectum, hypothalamus and pituitary; 3 hindbrain containing cerebellum and medulla.
For each experiment six couples were used and the experiment was repeated 4 times.
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On day 9 the treated fish was placed with its control partner. This time was chosen as zebrafish are sexual active immediately after illumination [ 30 ]. Male and female mating behavior and spawning was recorded. The tail fin of the exposed female was cut to identify it from the control female.
On completion of the behavior studies, the fish were euthanized and sex was determined by gonadal morphology. Four biological and two technical replicates were used to study gene expression and the transcript levels were normalized using a housekeeping gene, elongation factor 1a1 ef1a1. To avoid use of cross plate reference, each gene was run in one plate. Heat map for analyzed transcript levels were generated using Tableau software, version 8. For the behavioral studies, the untreated couples male—female or female—female couples were used as controls.
Principal component analysis PCA is a multivariate data analysis method that incorporates all the data and variables to determine the principal components contributing to the correlation patterns of the data by giving low preference to variables that show non-significant variance and identifying variables and data showing significant variances.core1.lga02.nsone.net/hijos-de-las-mentiras.php
A score plot showing sample grouping and a loading plot indicating the relationship between the variables was used in the analysis. Sex specific behavior including mating behavior, aggression and territorial marking is very common among sexually reproducing animals. During development the male and female brain become differentially organized and both steroid hormones and prostaglandins can activate and alter sexual behavior in mammals as well as in teleosts. In the present study we aimed to determine the influence of exogenously administered sex hormones and prostaglandins on zebrafish mating behavior, spawning and fecundity.
Furthermore, analysis of gene expression of male and female zebrafish brains, as well as the effect of E2 exposure was performed to identify sex dependent differences in gene expression. In another study EE2 exposed zebrafish males that did not undergo complete sex-reversal but that had reduced testis size or rudimentary ovaries were able to induce spawning behavior when placed with control female [ 35 ].
In a separate study it was shown that exposure of zebrafish to low levels of EE2 had no effect on male behavior but rendered the females less interest in EE2 exposed males [ 36 ]. Exposure to E2 has been shown to result in decreased male reproductive behavior in other teleosts as well [ 17 — 19 ].
Behavioral change and spawning. The steroid hormones experiments were performed with 24 fish while 12 fish were used for prostaglandin exposures. In this study we did not observe spawning egg release from control females when paired with KT exposed females. However, as spawning behavior is very similar to aggressive behavior we cannot differentiate between mating behavior and aggressive behavior using the present setup.
Since, PGE 2 and PGD 2 are known to influence sex differentiation in zebrafish [ 20 ] and as PGE 2 is involved in masculinization of female mice [ 10 ], we included these two prostaglandins to determine whether they could alter sexual behavior. The roles of prostaglandins in zebrafish sexual behavior clearly require additional studies. Zebrafish whole brain transcriptomic analyses have identified sexually dimorphic gene expression patterns [ 26 — 28 ]. In order to achieve better resolution we dissected the brain into three regions. This allowed us to determine region-specific expression patterns and to identify sex differences in gene expression.
In addition we exposed zebrafish to E2 to determine its role in region specific alteration in gene expression and steroid hormone mediated alterations in sexual behavior. A set of 32 genes was selected for analysis. The selection was based on their involvement in brain functions, sex differentiation and stress responses. Of these genes the gabbr1a , mbpa , mtf1 , ptges and sirt1 genes showed intermediate expression in the midbrain and the lowest expression levels in the forebrain.