Intra-abdominal thermosensitivity in the rabbit as compared with spinal thermosensitivity

Summary In rabbits, intra-abdominal temperature sensors of the dorsal wall of the abdominal cavity were selectively stimulated by means of thermodes perfused with water of temperatures ranging from 12–50°C. Respiratory acceleration and vasodilatation of the skin could be elicited as thermoregulatory responses by intraabdominal warming. By intra-abdominal cooling a depression of an elevated respiratory frequency could be induced. This depressing effect was already fully developed at a perfusion temperature of 36°C and could not be further augmented by stronger cooling.Neural afferent activity recorded from filaments of the N. splanchnicus was found to increase with rising perfusion temperatures beginning with 36–37°C. It is concluded from these results that abdominal thermosensitivity is predominantly a warmth-sensitivity in contrast to spinal cord thermosensitivity which comprises both cold and warmth sensitivity.Heating intensities and heat inputs, respectively, of equally effective periods of spinal cord and intra-abdominal warming were compared with each other. It was found that heat input into the abdominal thermode had to be four times greater than that supplied to the vertebral canal thermode in order to evoke identical responses. Simultaneous application of equally effective thermal stimuli to the abdomen and the spinal cord reinforced the thermoregulatory responses.