Sexual differentiation of the brain: a model for drug-induced alterations of the reproductive system
The process of the sexual differentiation of the brain represents a valuable model system for the study of the chemical modification of the mammalian brain. Although there are numerous functional and structural sex differences in the adult brain, these are imposed on an essentially feminine or bipotential brain by testicular hormones during a critical phase of perinatal development in the rat. It is suggested that a relatively marked structural sex difference in the rat brain, the sexually dimorphic nucleus of the preoptic area (SDN-POA), is a morphological signature of the permanent or organizational action of estradiol derived from the aromatization of testicular testosterone. The SDN-POA of the male rat is severalfold larger in volume and is composed of more neurons than that of the female. The observation that the mitotic formation of the neurons of the SDN-POA is specifically prolonged has enabled us to identify the time course and pathway of neuronal migration into the nucleus. Study of the development of the SDN-POA suggests that estradiol in the male increases the number of neurons which survive a phase of neuronal death by exerting a neurite growth promoting action and/or a direct neuronotrophic action. Finally, although it is clear that gonadal hormones have dramatic permanent effects on the brain during perinatal development, even after puberty and in adulthood gonadal steroids can alter neuronal structure and, perhaps as a corollary to this, have permanent effects on reproductive function. Although the brain may be most sensitive to gonadal hormones or exogenous chemical factors during perinatal development, such as sensitivity does not appear limited to this period.
- Research Organization:
- Univ. of California, Los Angeles, CA (United States)
- OSTI ID:
- 6515055
- Journal Information:
- Environ. Health Perspect.; (United States), Vol. 70
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
BRAIN
MORPHOLOGICAL CHANGES
ONTOGENESIS
SEX DEPENDENCE
TRITIUM COMPOUNDS
TRACER TECHNIQUES
ADULTS
DRUGS
ESTRADIOL
RATS
REPRODUCTION
TESTOSTERONE
THYMIDINE
TOXICITY
AGE GROUPS
ANDROGENS
ANDROSTANES
ANIMALS
AZINES
BODY
CENTRAL NERVOUS SYSTEM
ESTRANES
ESTROGENS
HETEROCYCLIC COMPOUNDS
HORMONES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
KETONES
LABELLED COMPOUNDS
MAMMALS
NERVOUS SYSTEM
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PYRIMIDINES
RIBOSIDES
RODENTS
STEROID HORMONES
STEROIDS
VERTEBRATES
560300* - Chemicals Metabolism & Toxicology
550801 - Morphology- Tracer Techniques