BISC 421 1st Edition Lecture 34 Outline of Current LectureI. Higher Brain Functions (end) II. Sex DifferencesCurrent LectureHigher Brain Functions (end)• Male moths have antenae specializedfor detection of female pheromones.• Sensory neurons project to the macroglomerular complex which is enlarged in the male.• Addition of male antenae to a female earlyin development causes a macroglomerular complex to form•Females release pheromones-‐ canmales detect?•Male: macroglomerular process, structure not found in the female-‐ projection site for the specialized antenna•Dimorphism being driven by external sensory structures•Could be a very long lasting effects of hormones•Indirect effect of sex hormones on muscles, mold neural circuit•Or could directly affect neurons•We are able to develop into both males and females•SRYtestes (don't worry about specifc pathways)-‐ more testosteroneSpinal nucleus of the bulcocavernousAttrophies in female because muscle fails to develop•Spinal nucleus of the Bulcocavernous – sexually dimorphic only in males•This nucleus controls the penis•Muscle maintained in those males who have testosterone, a trophic factor•Female makes muscle but does not maintain it-‐ degenerates•There are also effects in female that are missing in male but not whatwere focusing on.Sex steroid receptors are found in cortical regions as well as regions classically thought to be involved in sexually dimorphic behaviors.•You can look for the expression of these receptors in the brain-‐ dots indicate where receptors are•Steroid hormone receptor is a NUCLEAR receptor (not cell surface)-‐ could directly affect synaptic transmission.In testosterone treated embryonic spinal cord neurons, processes become thicker and more branched. Estradiol treated explantof hypothalamus (right) has more neurites than control.•Processes become thicker•Hypothalamus did have receptors for steroid hormones•Estradiol treated does have more neuritis and more branching unclear what this does to animals behavior •Female has more chromosomal content/genes•X inactivation: only one X active in each cell body•Females mosaic for expression of genes on X chromosome-‐ happens in a random way, neighboring cells have different X chromosomes that are active•SRY: directs formation of gonads, no role in nervous system, but several other genes on Y chromosome only found in males •Testosterone: generated from cholesterol, can go on to make estradiol and active form of testosterone•Altered enzymes in pathways can alter biosynthesis•Females producing quite a bit of testosterone not actually testes but masculine looking testosterone; male-‐associated behavior, aggression, ofen choose female partners, good athletes (if they have UP testosterone)•Males that look like females (opposite)•Caused by mutation in testosterone receptor•Male sex hormones come later in life•Problem in 5 Alpha reductase-‐ not able to be converted to dihydratestosterone•Raised as girls so all of a sudden they male testosterone and their genitalia change•Quite prevalent in Dominican republic-‐ boys raised as girls but show masculinebehavior and eventually developed male genitalia•These children may still be making dihydrotestosterone in brain so that's why they act as malesOxytocin and Vasopressin: bonding• males and vasopressin (prairie voles)!• involved in pair bonding!• females and oxytocin (prairie voles)!• oxytocin spikes at mating yield bonding activity!• oxytocin antagonists block bonding!• give to non-mated females and they bond to males!• oxytocin spikes at pup birth yield maternal behaviors•What is driving pair bonding? ( like in penguins)•Vasopressin in male•Oxytocin in femalesVaosopressin and pairbondingArginine vasopressin (same as antidiuretic hormone)!Vasopressin is a peptide hormone that controls the reabsorption of molecules in the tubules of the kidneys (concentrates urine)•Prairie vole is much more likely to spend time with partner than stranger and the meadow vole does not•The difference is in the brain: see that th receptor for the vasopressin is more highly expressed in the prairie voles than the meadow voles (in the ventral paladin)•Small peptide hormone produced by the hypothalamus-‐ has other roles than this but this is one of the roles•The oxytocin that is released in the bloodstream cant cross the blood brain barrier but it is actually released by centrally projecting neuronsOxytocinfemales and oxytocin (prairie voles)• oxytocin spikes at mating yield bonding activity• oxytocin antagonists block bonding!• give to non-mated females and they bond to males• oxytocin spikes at pup birth yield maternal behaviors•Take measurement of oxytocin in the female, spikes at mating•Use antagonists to block oxytocin and see that it blocks bonding•Variation in the vasopressin receptor-‐ polymorphism in the population (humans)•Does this relate to fidelity?•This was proved to be
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