Sammendrag
Since spinal thermosensitivity seems to be much more important than that of the hypothalamus in evoking appropriate thermoregulatory reflexes in birds, this has formed the subject of a number of studies. Appropriate thermoresponses during spinal cooling have been demonstrated for several species, e. g. the pigeon (Rautenberg et al., 1972), the Adelie penguin (Hammel et al., 1976), the goose (Helfmann et al., 1981) and the Pekin duck (Inomoto and Simon, 1981). The local thermosensitivity of the thermosensory areas that have been identified has been determined by studying the maximum response of a thermoregulatory effector to an experimentally induced temperature change. The spinal cord of the pigeon, in particular, is highly sensitive with changes in heat production being linearly related to changes in the spinal cord stimulus. Values of between -0.9 and -2.05 W kg-1 °C-1 for the spinal sensitivity have been recorded for this species (Graf, 1980; Rautenberg, 1969). This vide range of values may be partly due to the use of different experimental methods. A general problem in assessing effector sensitivity to thermal stimulation of the spinal cord using the thermode technique, has been the difficulty in defining the stimulation temperature. The exact location of the temperature-transducing elements within and/or close to the spinal cord is not yet known wherefore their actual temperatures cannot be determined precisely.