THE CAPACITY TO ACCUMULATE CYCLIC-AMP IN THE PREOPTIC-ANTERIOR HYPOTHALAMIC AREA OF THE RAT IS AFFECTED BY THE EXPOSITION TO LOW AMBIENT-TEMPERATURE AND THE SUBSEQUENT RECOVERY

The accumulation of adenosine 3':5'-cyclic monophosphate (cAMP) was me asured in the preoptic-anterior hypothalamic area, the cerebral cortex , and the hippocampus of rats exposed to different ambient temperature s: (1) 23+/-0.5 degrees C, for 53 h+/-20 min (control);(2) -10+/-1 deg rees C, for 53 h+/-20 min (exposure to low ambient temperature);(3) -1 0 degrees C for 48 h and 23 degrees C for the following 5 h+/-20 min ( recovery). The capacity to accumulate cAMP was tested by subjecting an imals to acute hypoxia, a stimulus which is known to induce a large in crease in brain cAMP concentration. In the control condition, hypoxic stimulation increases cAMP concentration in all the brain regions stud ied. In contrast, during the exposure to low ambient temperature, whil st both the cerebral cortex and the hippocampus show the same levels o f accumulation found in the control condition, cAMP accumulation is re duced in the preoptic-anterior hypothalamic area. However, during the first few hours of the recovery period, the preoptic-anterior hypothal amic area is able to reattain the capacity for cAMP accumulation obser ved in the control condition.