Responses of neurons in the preoptic area to temperature, serotonin, and epinephrine

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Abstract
The response of single units in the preoptic-septal area of the dog to changes in local tissue temperature and to the central and peripheral administration of serotonin [5-Hydroxytryptamine] and epinephrine was studied. Analogue simulation of the thermal characteristics of the tissue mass was carried out permitting precise estimates of tissue temperature at the particular neuron location. Certain units showed changes in firing rate which correlated with tissue temperature changes occurring at locations at some distance from the neuron. Such units are possibly components of an efferent pathway rather than primary thermal receptors. When serotonin was administered intraventricularly both temperature-sensitive and temperature-insensitive units demonstrated a reduction in discharge rate. Temperature-insensitive units were variable in their responses to the intravenous adminstration of serotonin, but temperature-sensitive units were most often characterized by an increase in firing rate. Intraventricular administration of epinephrine was generally followed by a reduction in the activity of temperature-sensitive units whereas temperature-insensitive neurons were more variable. Similar variability was observed following the intravenous administration of epinephrine. The net effect of central administration of the amines is an over-all reduction in activity level within this area of the [central nervous system]. These findings do not support the proposed antagonistic role of serotonin and epinephrine in maintenance of body temperature.