Pubertal Development of Brain and Behavior

Michigan State University, East Lansing MI

Investigators

Abstract

The primary functions of the nervous system are to sense, interpret, and integrate external and internal stimuli and to generate appropriate behavioral responses. The influence of external and internal stimuli on the nervous system and behavior changes across the life span. In particular, puberty is a period of development during which significant neural and physiological changes result in the emergence of adult behaviors. Maturation of the nervous system during pubertal development results in different responses to external and internal stimuli in adulthood. The overall objective of this research is to understand developmental events during puberty that alter the integration of external and internal stimuli within behavioral neural circuits. This project focuses on pubertal maturation of the neural circuit that mediates male mating behavior in the hamster. The perception of olfactory cues from a female and the presence of circulating steroid hormones are both obligatory for mating behavior in this species. These sensory and hormonal stimuli activate neurons within a well-characterized neural circuit in the adult, and the neural integration of these external and internal cues leads to expression of mating behavior. Previous research has determined that olfactory stimuli and steroid hormones do not impact the nervous system of juvenile males in the same way, and therefore mating behavior is not expressed. This project will investigate pubertal change in the interactions among steroid receptors and neurochemical responses to olfactory cues. The working hypothesis is that in the adult nervous system, the cellular basis for the integration of sensory and hormonal information involves activation of progesterone receptors by neurotransmitters or neuropeptides released in response to female olfactory cues. We hypothesize that such sensory/hormonal integration is not accomplished prior to puberty for two reasons: 1) estrogen does not induce progesterone receptors in neurons of the hypothalamus of juvenile males; and 2) female olfactory cues do not elicit the neurotransmitter or neuropeptide responses needed for activation of the progesterone receptor in prepubertal males. Experiments are designed to test both aspects of this hypothesis, which is proposed to account for the inability of juvenile males to express mating behavior. This project will contribute to our understanding of the cellular mechanisms underlying pubertal maturation of the neural integration of sensory and hormonal stimuli required for expression of adult-typical behaviors.