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LINKS: ....Bird Flu Info ....Your Memory Enhancer ....Neurotech ....Success Tips ....Free Hormones, Sex, And The BrainA psychologist at Columbia University's department of psychiatry, Heino Meyer-Bahlburg, for example, is interested in the effects of prenatal sex hormones on human behavior. He is studying patients with endocrine disorders like congenital adrenal hyperplasia, in which the patients were exposed to excessive levels of testosterone, the male hormone, while still in the womb. "Genetic females--with two X chromosomes--exposed to testosterone prenatally are very tomboyish as children," he says. "As adults, they show higher rates of bisexuality, and some even go on to change their gender to male." Meyer- Bahlburg adds that with currently available medical technology, behavioral studies are still the best gauge of the effects of prenatal hormones. "It would be interesting to examine the brain structures, particularly nuclei in the limbic system," he says, "but current imaging techniques are just not powerful enough. Biopsies are obviously not an option." Scientists are not confining hormone/behavior studies to humans alone, as is evident from several articles that appeared in the scientific and popular press recently (N. Angier, New York Times, Nov. 12, 1991, page C1, and Aug. 31, 1993, page C1 [articles on cichlid fish]; N. Angier, New York Times, Nov. 2, 1993 [prairie voles]; see reading list on page 16 for magazine/journal articles). Carole Carter-Porges of the University of Maryland, College Park, is one of many biologists who are studying the mating habits of prairie voles, a rare breed of animal that has a monogamous lifestyle, with the male of the species actively helping in rearing pups. Recent data from the laboratories of Carter-Porges and others indicate that such behavior is related to vasopressin, a peptide hormone released in males soon after mating. Furthermore, the synthesis of vasopressin appears to be controlled by testosterone. "Our studies with voles show that there is a definite chemical and biological basis for social bonding and behavior," says Carter-Porges. In an interesting twist, Stanford University neurobiologist Russell D. Fernald has shown that, among cichlid fish at least, socio-sexual behavior induces changes in the brain and hormone levels, rather than the other way around. The size of the hypothalamus of the male--the region of the brain responsible for the fish's breeding abilities--is directly and profoundly affected by the cichlid's social status. As the fish battle one another for breeding territory, the hypothalmic cells of the dominant male become six to eight times larger in size, but will shrink back when challenged by a more aggressive male. These cells produce the gonadotropin-releasing hormone, GnRH, that normally regulates the sex organs; shortly after the brain cells shrink, testes of the fish follow suit. Fernald is currently researching the molecular mechanisms of the transformation, and the role of GnRH in the process. "The GnRH molecule is the same in all animals across evolution and even related to the yeast mating factor [the equivalent of a sex hormone in yeasts, which are not animals]," says Fernald. Thus, while he does not yet know if GnRH-producing cells undergo size changes in humans, his findings could have a great impact on the understanding of human sexual behavior and its control. HOME...... Brain Food LINKS: ....Medical Dictionary ....Stress Management ....Allergy Info |