Neuronal responses to cutaneous electrical and noxious mechanical stimuli in the nucleus reticularis thalami of the rat.

Responses of 81 neurons accurately localized in the nucleus reticularis thalami (RT) of moderately anesthetized rats were tested for response to noxious and non-noxious cutaneous stimuli. Spontaneous firing rates were very high (between 18 and 60 Hz) and regular. Non-noxious stimuli did not modify the activity of RT neurons. By contrast, in 62/81 RT neurons, noxious cutaneous mechanical stimuli induced a strong and short-latency depression of firing, irrespective of the location of the stimulus on the body surface. Intense (> 3 mA) transcutaneous electrical stimulation also elicited long-lasting depressions of the firing in most cases. The hypothesis of a possible role of the RT nucleus in inhibitory controls exerted upon noxious messages relayed in the thalamic ventrobasal nucleus is discussed.