Comparison between hypothalamic thermoresponsive neurons from duck and rat slices.
Neuronal thermoresponsiveness in the preoptic and anterior hypothalamic (PO/AH) region of a bird and a mammal were compared in vitro by recording the activity of 48 units from ducks and 37 units from rats in tissue slices subjected to temperature changes. Warm-responsive units were found in similar proportions in duck and rat PO/AH slices. The average degrees of thermoresponsiveness did not differ between the two species. Neurons exhibiting thresholds of warm responsiveness had higher threshold temperatures (2P less than 0.01) in duck (38.8 +/- 0.2 degrees C) than in rat (37.4 +/- 0.4 degrees C) slices (means +/- standard errors). Firing rates at threshold temperatures and thermoresponsiveness below and above thresholds did not differ between ducks and rats. During synaptic blockade in a Ca2+-free/high-Mg2+ medium, warm-responsiveness was retained in 9 out of 13 units in duck slices and in 8 out of 13 units in rat slices. In two instances in ducks and in one case in rats positive temperature coefficients were converted into negative temperature coefficients. Among two cold-responsive units tested in duck slices one retained its cold-responsiveness. It is concluded that in vitro evaluation of PO/AH neuronal thermoresponsiveness in a bird and a mammal has not revealed differences at the single unit level which might explain the diverging contributions of the avian and mammalian hypothalamus to deep body temperature perception.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D007025:Anterior Hypothalamic Nucleus / Q000502:physiology*; D002118:Calcium / Q000502:physiology; D004372:Ducks; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D011301:Preoptic Area / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity; D013823:Thermoreceptors / Q000187:drug effects / Q000502:physiology*
D008274:Magnesium; D002118:Calcium