Interactions of temperature and angiotensin II in paraventricular neurons of rats in vitro.

We recorded extracellular impulse activity of hypothalamic paraventricular neurons ( n=75) in rat brain slices during application of angiotensin II (ANG II, 10(-9)-10(-6) M) and/or temperature changes (32-42 degrees C). ANG II, with a threshold concentration of 10(-8) M, increased the firing rate in more than 80% of the neurons with strongest excitations occurring in bursting neurons. Increasing the temperature also raised the discharge rate in the majority of the neurons, often together with enhanced burst discharges. When ANG II was applied during ongoing sinusoidal temperature changes, its effects were more pronounced at elevated temperatures. These electrophysiological data illustrate that stimulus-encoding properties at the neuronal level can contribute to the interactions between osmoregulatory and thermoregulatory mechanisms including mutual sensitization when different stimuli (here: ANG II and temperature changes) are applied simultaneously.