2 The Sexual Brain

The Sexual Brain

The Hypothalamus Integration of Neuroendocrine Activity and Genesis of Instinctive Drives & Behavior Ganong, William F. REVIEW OF MEDICAL PHYSIOLOGY 22 nd ed. Lange Medical Books/McGraw-Hill (2005)

Ganong, William F. REVIEW OF MEDICAL PHYSIOLOGY 22 nd ed. Lange Medical Books/McGraw-Hill (2005)

Hypothalamic Functions: Homeostasis and Instinctive Drives & Behavior Ganong, William F. REVIEW OF MEDICAL PHYSIOLOGY 22 nd ed. Lange Medical Books/McGraw-Hill (2005)

Hypothalamus – Pituitary – Gonad Intercommunication Ganong, William F. REVIEW OF MEDICAL PHYSIOLOGY 22 nd ed. Lange Medical Books/McGraw-Hill (2005)

Menstrual Cycle Is Orchestrated by Hypothalamus Ganong, William F. REVIEW OF MEDICAL PHYSIOLOGY 22 nd ed. Lange Medical Books/McGraw-Hill (2005)

Cyclic Ovarian Secretion Men: Estradiol = 50 ug/d, Testosterone = 4000-9000 ug/d Ganong, William F. REVIEW OF MEDICAL PHYSIOLOGY 22 nd ed. Lange Medical Books/McGraw-Hill (2005)

Sex Hormones Before Birth Versus After Birth

Female monkeys and humans exposed to androgen or excess estrogen in utero

Still have female cyclic gonadotropin secretion

Adult sexual behavior altered

Sex hormone administration to adults

Increases sexual activity

But does not change sexual orientation

Ganong, William F. REVIEW OF MEDICAL PHYSIOLOGY 22 nd ed. Lange Medical Books/McGraw-Hill (2005)

Sexual Behavior Region in Rodents

Sexually dimorphic nucleus of preoptic area (SDN-POA)

First discovered in rodents

In region of hypothalamus with known sexual function

Control of masculine sexual behavior

Release of gonadotrophic hormones producing ovulation

Paredes, Raul G., and Baum, Michael J. Role Of The Medial Preoptic Area/Anterior Hypothalamus In The Control Of Masculine Sexual Behavior ANNUAL REVIEW OF SEX RESEARCH (1997)

Human Anterior Hypothalamus

Four nuclei in preoptic area (interstitial nuclei of anterior hypothalamus)

INAH1, INAH-2 and INAH-3 are sexually dimorphic (more cells & volume in males)

SDN-POA of humans

Horseshoe-shaped, comprised of INAH1 & INAH2

Aka intermediate nucleus

Uncinate nucleus of humans

INAH3 & INAH4 are subnuclei

horseshoe-shaped nucleus divided by fornix

Allen, L. S., Hines, M., Shryne, J. E., and Gorski, R. A. Two Sexually Dimorphic Cell Groups In The Human Brain. JOURNAL OF NEUROSCIENCE, 9: 497-506 (1989)

Uncinate Nucleus of Human & Rhesus Monkey May Be Homologous to SDN-POA of Rat

Rhesus monkey hypothalamus has nuclei that resemble the first, second and third interstitial nuclei of the anterior hypothalamus (INAH1-3) of the human

Positional and cytoarchitectonic criteria suggest that of these nuclei, INAH3 and its potential counterpart in the rhesus monkey are the best candidates for homology with the SDN-POA of rat

Byne, William. The Medial Preoptic And Anterior Hypothalamic Regions Of The Rhesus Monkey: Cytoarchitectonic Comparison With The Human And Evidence For Sexual Dimorphism. BRAIN RESEARCH 793: 346-350 (1998)

Hypothalamus & Limbic System: Genesis of Emotions & Emotional Expression Netter, Frank H. The CIBA COLLECTION OF MEDICAL ILLUSTRATIONS. Vol I. Nervous System. Part I. Anatomy & Physiology. New York: CIBA (1983)

Limbic Functions