Temperature dependence of signal processing in nucleus tractus solitarius (NTS) 2nd‐order neurons in Syrian hamsters

Abstract

Previous studies involving EEG measurements indicate that during hibernation, cortical and hippocampal activity is highly attenuated, but brainstem cardiorespiratory reflexes appear to remain actively involved in maintaining homeostasis. We tested the hypothesis that at low temperatures, neurons in the NTS change their properties yet retain their ability to support signal processing over central reflex pathways. Using patch clamp techniques, we measured the temperature dependence of signal processing in 2nd‐order neurons in NTS slices from euthermic Syrian hamsters (Mesocricetus auratus). The amplitude and onset latency of EPSCs evoked by sensory afferent stimulation were similar at 33°C and 24°C. At 15°C, there was a 77% decrease in amplitude and 4‐fold increased in onset latency. Spiking responses to depolarizing current injections linearly decreased as temperature dropped from 33°C to 15°C (p<0.001). This decreased spiking response was associated with changes in action potential waveform: a significant increase in peak amplitude (19mV) and a 5‐fold increase in width. Data are consistent with our hypothesis and suggest that decreased synaptic transmission and spiking response may be offset by an enhanced amplitude and duration of action potentials to preserve signal processing. (Support: R01 HL091763)