Neuroendocrinology
Bradley E. Alger
Gary Fiskum, Ph.D.
Joel D. Greenspan, Ph.D.
John Hamlyn, Ph.D.
Gloria E. Hoffman, Ph.D.
James I. Koenig, Ph.D.
Margaret M. McCarthy, Ph.D.
Istvan Merchenthaler, MD, PhD, DSc
Jessica Mong, Ph.D.
Elizabeth Powell, Ph.D.
Mark Rizzo, Ph.D.
James Russell, M.D.
Leonardo Tonelli, Ph.D.
Richard J. Traub, Ph.D.
Yonathan Zohar, Ph.D.
Mission: The goal of researchers
in the Neuroendocrinology Research Focus Group is to further
the understanding of the basic mechanisms controlling reproduction,
the development and maintenance of sex differences in the brain,
and an individuals response to stress.
Understanding these basic processes
is central to the development of treatments for infertility and contraception.
Findings in this area are also important to refining the diagnosis
and treatment of neurological disorders that are gender biased such
as major depression, anxiety disorders, attention deficit / hyperactivity
disorder, obsessive compulsive disorder and autism. The potential
contribution to all of these processes by chemicals in the environment
that act as endocrine disrupters is an additional focus.
Research
Neuroendocrinology is the study of how
the endocrine system impacts the nervous system and conversely how
the nervous system regulates the endocrine system. Hormones are blood-borne
molecules released from the endocrine glands, the ovaries and testes,
as well as the adrenal glands, thyroid gland, pancreas and placenta.
All of these secrete substances that alter how the brain functions
and can influence a broad range of activities. These include:
Reproduction A class of hormones
that are of particular interest are the so-called sex steroids, estradiol,
progesterone and testosterone, which are synthesized by and secreted
from principally the gonads. These powerful chemicals influence the
brain throughout life. Beginning in utero and extending into early
life, estradiol and testosterone determine whether the developing
brain will be masculinized or feminized. At puberty, these steroid
hormones again become important in regulating the reproductive cycles
of females and reproductive function in males. The activity of a
particular group of neurons in the brain, the GnRH (gonadotropin
releasing hormone) neurons, is fundamental to the control of both
male and female reproduction. Despite recent technological advances
in cloning and artificial insemination, most reproduction still involves
the mating of a male and female. Steroid hormones act in the brain
to motivate animals (and humans) to copulate. Successful mating is
followed by pregnancy, which results in a unique hormonal environment.
Prolactin is a hormone released from the pituitary that is at particularly
high levels during pregnancy and acts as a natural contraceptive.
Progesterone is also at very high levels during pregnancy and this
steroid might protect the brain from damage. The control of reproductive
behavior and the consequences of pregnancy on neuronal functioning
are also active areas of research by the program.
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In addition to neurons, glia are also cells in
the brain that are highly responsive to steroid hormones such
as estrogen. Pictured here in green is a glial cell located
in the hypothalamus, a brain area critical for the control
of reproductive functions. The nucleus of the glial cell is
stained red, as is the nuclei of nearby neurons. Research by
members of the Neuroendocrinology Focus Group has demonstrated
that glia cells change their shape when exposed to estrogen
and that this has profound consequences for the synapses made
by neighboring neurons.
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Challenges for the Future
The post-genome era is an exciting
one for the field of neuroendocrinology. Understanding the genetic
basis of variability in physiology and behavior is an important
stepping stone in establishing both the normal and abnormal responses
of cells. Hormones are often the means by which signals from the
environment are relayed to the organism, as they will vary in response
to light, food, temperature, stress and population crowding, allowing
the animal to adapt to challenges. It has recently been found that
some pesticides and agents used in the generation of plastics can
act as hormone mimetics, so-called endocrine disrupters, and can
alter the normal functioning of the endocrine system and disrupt
the delicate balance between the brain and body. The greater our
understanding of the basic cellular processes regulated by hormones,
the better our ability to detect subtle but detrimental effects
of environmental contaminants.
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