Thermosensitivity of preoptic neurones in a hibernator (golden hamster) and a non-hibernator (guinea pig)

Summary

Thermosensitivity of preoptic units was studied at hypothalamic temperatures (T _hy) ranging from 8–43°C in golden hamsters in a non-hibernating state as well as in guinea pigs. In golden hamsters 2 types of thermoresponsive preoptic neurones were found: 1. Neurones sensitive toT _hy ranging from 10–42°C with an exponential characteristic and very high spontaneous firing rates (29–59 imp/s) atT _hy 36–37°C. 2. Neurones with a bell-shaped temperature-firing rate characteristic, a negative temperature coefficient atT _hy 40–30°C, a maximal activity atT _hy 20–30°C and a positive temperature coefficient (+0.8 to +4 imp/s·°C) even atT _hy close to 10°C. In guinea pigs thermoresponsive preoptic units became inactive or insensitive to thermal stimulation as soon asT _hy fell below 30°C. These results suggest that in hibernators central nervous structures involved in temperature regulation are adapted to maintain their function over the wide range of core temperatures which occur during the different phases of hibernation.