ORGANIZATIONAL EFFECT OF HORMONES

ORGANIZATIONAL EFFECT OF HORMONES

INTRODUCTION:

Arnold Adolph Berthold was a German physiologist and Zoologist, who in 1849, had a question about the function of testes. He noticed that the castrated roosters that they did not have the same sexual behaviors with roosters with their testes intact. He decided to run an experiment on male roosters to examine this phenomenon. He kept a group of roosters with their testes intact and saw they had normal sized wattles and combs, a normal crow and normal sexual and aggressive behavior. He also had a group with their testis surgical removed and noticed that their secondary sexual decreased in size, had a weak crow did not have sexual attractions toward females, and were not aggressive. He realized that this organ is essential for these behavior but he did not know how. To test this further, he removed one testis and placed in abdominal cavity. The roosters acted and had normal physical anatomy. He was able to see that location of testis does not matter. He wanted to see if it was genetic factor then he transplanted testis of another rooster to a rooster and see that there is no difference in physical anatomy. Berthold determined that the location and genetic factors of testis do not matter in the relation to sexual organs and behavior but some chemicals in testis being secreted is causing this phenomenon. It was later identified that this factor was hormone, testosterone.

So, the basic concept of hormones was given by Berthold by performing experiment on roosters.

HISTORY:

William Bayliss and Ernst Starling, a physiologist and biologist respectively, wanted to see the nervous system has an impact on digestive system. They performed an experiment in 1902.

They knew that pancreas was involved in the secretion of digestive fluids after the passage of food from stomach to intestine which they believed to be due to nervous system. They cut the nerves to pancreas in animal model and discovered that it was not nerve impulses that controlled the secretion from pancreas. It was determined that a factor secreted from the intestines into blood was stimulating the pancreas to secrete the digestive fluids. This factor named, secretin, a hormone, although the term hormone was not coined until 1905 by Starling.

Thus, the HORMONE is defined as:

“A regulatory substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells and tissues into action is called hormone”.

EFFECTS OF HORMONE:

There are two primary effects of hormone:

1. Organizational effect of hormone
2. Activational effect of hormone

ORGANIZATIONAL EFFECT OF HORMONES:

“It involves hormonal effects during critical periods in behavioral development, which produce relatively permanent changes in nervous system and other tissues”.

This effect states that steroid hormone permanently organize the nervous system during early development which is reflected in adult male and female typical behavior.

Main points of organizational effect:

There are three main components of this effect:

1. Organizational effect is permanent: It showed that organizational effect can last for long time. New born female mice were exposed to either bear one minute of neonatal handling procedure for first days after birth or were not handled at all. As adult, sexual receptiveness was recorded and handled female mice showed less Lordosis than non-handled female mice and had less progesterone serum. Neonatal handling not only affected reproductive behavior, but also affected sympathetic nerve activity and glucocorticoid levels into adult, indicating that emotional stress during developmentally sensitive periods can permanent change behavior.

2. Organizational effect occurs just prior to or after birth but before neural tissues matured: It demonstrated the importance of timing of hormonal influence in a study involving rats and size of their medial preoptic nucleus (MPON). (MPON) size is sexually dimorphic trait in that the MPON of male rats are larger than the MPON of female rats. But when male rats were castrated neonatally, their MPON was significantly smaller than male rats that were castrated after their brain was sexually differentiated. Despite both groups of males being castrated, the timing of castration affected MPON size, indicating that organizational effects occur prior to maturation of neural tissues.

3. Organizational effects take place during critical period: It indicate that organizational effects are maximized during sensitive periods of brain development. One critical period is weeks 8-24. Another sensitive period shortly after may exist with a peak in a testosterone in male infants during postnatal months 1-5.

Organizational effect of testosterone on male brain:

In this figure, we see what happen to adult behavior of male through tree different treatment

1. Castrated as an adult
2. Castrated as at birth with no supplemental testosterone
3. Castrated at birth with supplemental testosterone administrated.

Treatment 1 and 3 results in adults that behave as males whereas treatment 2 results in adult with female behavior. What this shows that there is a crucial period early in postnatal life of a rat during which either the presence of functioning testicles or externally administrated testosterone causes male brain development to occur. In the absence of either, the rate ends up with a female brain and female adult behavior despite being physically and genetically male. The period of development is roughly equivalent to gestation 20 through birth during human pregnancy.

Organizational effect of estrogen on female:

This figure illustrates what happens to female treated similarly. Here only the 3 treatment results in adult with male behavior. This is because ovaries don’t produce much testosterone. So eve n female spayed as adult do not have much testosterone present during critical period for sex of their brain.

Abstract of article:

Sexual differentiation of human behavior is influenced by sex hormones present during sensitive period of development (organizational effect), as occurs in other mammalian species. The most important sensitive period has been considered to be prenatal but there is increasing attention to puberty as another organizational period with the possibility of decreasing sensitivity to sex hormones across pubertal transition. Sex hormones present during puberty and pubertal periods produce permanent changes to behavior. There is a good evidence that exposure to