Pubertal Development of Brain and Behavior

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The primary functions of the nervous system are to sense, interpret, andintegrate external and internal stimuli and to generate appropriatebehavioral responses. The influence of external and internal stimuli onthe nervous system and behavior changes across the life span. Inparticular, puberty is a period of development during which significantneural and physiological changes result in the emergence of adultbehaviors. Maturation of the nervous system during pubertal developmentresults in different responses to external and internal stimuli inadulthood. The overall objective of this research is to understanddevelopmental events during puberty that alter the integration of externaland internal stimuli within behavioral neural circuits. This project focuses on pubertal maturation of the neural circuit thatmediates male mating behavior in the hamster. The perception of olfactorycues from a female and the presence of circulating steroid hormones areboth obligatory for mating behavior in this species. These sensory andhormonal stimuli activate neurons within a well-characterized neuralcircuit in the adult, and the neural integration of these external andinternal cues leads to expression of mating behavior. Previous researchhas determined that olfactory stimuli and steroid hormones do not impactthe nervous system of juvenile males in the same way, and therefore matingbehavior is not expressed. This project will investigate pubertal changein the interactions among steroid receptors and neurochemical responses toolfactory cues. The working hypothesis is that in the adult nervoussystem, the cellular basis for the integration of sensory and hormonalinformation involves activation of progesterone receptors byneurotransmitters or neuropeptides released in response to female olfactorycues. We hypothesize that such sensory/hormonal integration is notaccomplished prior to puberty for two reasons: 1) estrogen does not induceprogesterone receptors in neurons of the hypothalamus of juvenile males;and 2) female olfactory cues do not elicit the neurotransmitter orneuropeptide responses needed for activation of the progesterone receptorin prepubertal males. Experiments are designed to test both aspects ofthis hypothesis, which is proposed to account for the inability of juvenilemales to express mating behavior. This project will contribute to ourunderstanding of the cellular mechanisms underlying pubertal maturation ofthe neural integration of sensory and hormonal stimuli required forexpression of adult-typical behaviors.