The goal of this proposed study is to further the understanding of the role of the central nervous system in the regulation of body temperature. Fever will be used as a tool to achieve this aim. By observing the quantifying the alterations in thermoregulatory activity in response to fevers produced by preoptic anterior hypothalamic (PO/AH) injections of prostaglanding E1 (PGE1) we hope to obtain two tangible results. a) An understanding of how the peripheral and central elements of the thermoregulatory system integrate to produce a regulated body temperature and how this integration is altered to produce fever. b) Information on how pyrogens and other noxious stimuli act on the brain to raise the set point of the physiological thermoregulator and cause a controlled elevation of body temperature - fever. The plans necessary for the immediate testing of several hypotheses outlined in the proposal are delineated. 1) To correlate changes in PO/AH "set temperature" produced by PGE1 injections with changes in PGE1 concentration levels 2) To determine whether or not fever is due to changes in PO/AH thermosensitivity 3) To ascertain the mechanisms by which the physiological set point (if one exists) operates to establish a level of normal body temperature. The investigation of these problems by techniques, methods and equipment which we have developed in previous studies is outlined and discussed.