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BSTc region of brain & transsexualism

Jim Kohl jkohl at vegas.infi.net
Fri Feb 9 00:56:27 EST 1996

In article <31191109 at gate1.pbi.nrc.ca>, klai at pbi.nrc.ca says...
>Regarding Transsexualism-  Just a  query, if female-like BSTc regions 
>found in brains of transsexuals, then  why would transsexualism persist 
>the evolutionary scheme of thing?  Would such structural differences 
>through time, or vary?

Similar questions have been posed with regard to homosexuality. I posit 
that the answers to such questions will come from further study of the 
gonadotropin-releasing hormone (GnRH) neuronal system and of GnRH 
pulsatility--as it is influenced by social-environmental chemical 
stimuli, e.g., pheromones, via the olfactory systems. (Yes, I believe 
that humans have a functional vomeronasal organ and thus, perhaps, a 
functional accessory olfactory system.)

Given the mammalian model, pheromones appear to activate genes in GnRH 
neurosecretory neurons, thus altering GnRH pulsatility, gonadotropin 
secretion and steroidogenesis. The primary sex steroid hormones, 
estradiol and testosterone are believed to influence apoptosis, 
synaptogenesis, and synaptolysis--in effect, altering the neuroanatomical 
"size" of certain structures in the brain, as well as connectivity. Thus, 
there is little wonder that these (and other steroids) are also linked to 
behavior. But behavior may be prenatally predisposed by the development 
of the GnRH neuronal system, just as behavior may be altered by 
experiences assoiciated with social-environmental chemical stimuli.

Does anyone know of other social environmental stimuli, besides 
pheromones, that appear to alter gene expression in GnRH neurosecretory 
cells of tissue in the brain--an organ that is part of the organ system, 
which is most consistently linked to reproductive sexual behavior? If 
not, doesn't it seem likely that the concept of human pheromones may be 
used to explain a variety of animal behaviors?

Jim Kohl

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