Unit responses in the ventrobasal thalamus (VPL) of the cat of bradykinin injected into somatic and visceral arteries.

Under light to moderate sodium pentobarbital anesthesia one half of the thalamic neurons displaying place and modality specific responses to low intensity mechanical stimulation of contralateral receptive fields also responded, by excitation or by inhibition, to bradykinin injections into somatic and visceral arteries. Partial or complete somatovisceral convergence was commonly seen in neurons with otherwise typical lemniscal properties. The response intensities varied considerably for different neurons; the responses to somatic bradykinin were always stronger than to visceral injections. The time course of the response was comparable to that seen in peripheral nerves, other central sites, and the behavioral reaction to bradykinin. Control experiments indicated the independence of the bradykinin responses from variations in blood pressure or general arousal effects. It is suggested that modulation of ventrobasal thalamic activity may be an important factor in central nociceptive processing.