PRIMATE CIRCADIAN-RHYTHMS DURING SPACEFLIGHT - RESULTS FROM COSMOS-2044 AND COSMOS-2229

The circadian timing system (CTS) coordinates an animal's physiology a nd behavior both internally and with the 24-h day. Previous studies ha ve suggested that tile CTS is sensitive to changes in gravity. To exam ine this question, the expression of the CTS in four juvenile male rhe sus macaques (Macaca mulatta) were studied in space. These animals wer e flown on the Cosmos 2044 and 2229 missions. Activity, heart rate, an d axillary and brain (Cosmos 2229) temperatures were recorded. In both flights, tile subjects exhibited delays in the phasing of their tempe rature rhythms and a decrease in mean heart rate compared with ground control studies. These data are in support of other studies that demon strate that the CTS is sensitive to changes in the gravitational envir onment. Furthermore, the data also support the concept of a multioscil lator organization of the primate CTS due to the differential response s of the rhythms measured.