NEURAL BASES OF REPRODUCTIVE BEHAVIOR

The overall objective of this project is to determine how hormones interact with central nervous system effectors for reproductive behaviors. Our experimental approach combines techniques from behavioral neuroendocrinology, neuroanatomy, developmental neurobiology and neurophysiology. The focus of the present proposal is on the neural and hormonal control of vocal behaviors in the South African clawed frog, Xenopus laevis. This vertebrate experimental system offers sterotyped, sexually dimorphic reproductive behaviors under strict control by specific gonadal steroids. In the first set of experiments, we will investigate the hormonal control of two sex-specific reproductive vocal patterns: male mate calling and female ticking. The relative contributions of genetic and hormonal sex to the differentiation of behavioral repertoires will be determined. The existence of a "sensitive period" for hormone effect on behavior will be explored. In a second set of studies, we will map the central nervous system pathways for vocal control. The effects of sex-specific vocalizations on the reproductive behaviors and neuroendocrine state of males and females will be studied. The efferent vocal pathway and the afferent auditory system will be mapped anatomically. We will focus on intersections of limbic diencephalic projections with the calling pathways as these may provide the neuroanatomical bases for behavioral coordination of copulatory acts with vocalizations. In the final series of experiments, we will examine how sex hormones affect neural systems for reproductive behaviors. The activity and sensitivity of a sex hormone-concentrating midbrain auditory nucleus will be examined under different endocrine conditions. The sensitivity to sex hormones of neuroeffectors for reproductive behaviors will be examined in developing and adult stages. The distribution of steroid-sensitive CNS cells will be compared to the locations of cells and fibers containing the behaviorally important neuropeptiode, luteinizing hormone releasing hormone. The work proposed here forms a basis for understanding effects of hormones on behaviorally important neurons. Basic principles of endocrine-neural interaction underly future research in such clinically relevant problem areas as; the deermination of gender identity, the actions of oral contraceptives and hormonal control of fertility.