Spinothalamic lamina I neurones selectively responsive to cutaneous warming in cats

Abstract

1 In order to further characterize the role of lamina I as the source of central ascending neural pathways for thermoreception and thermoregulation, experiments were performed on anaesthetized cats to determine the quantitative response characteristics of warming-specific lumbosacral spinothalamic lamina I neurones. 2 We identified 10 neurones out of 474 that were selectively excited by cutaneous warming (Warm cells). Their thresholds were all in the range 35-37 °C at a baseline of 34.5 °C, and their discharge linearly encoded the temperature of graded, innocuous warming stimuli with a sensitivity of 2.1 Hz °C⁻¹. 3 The stimulus-response function of the Warm cells plateaued at temperatures that were in the noxious heat range. 4 The Warm cells were distinguished from other classes of spinothalamic lamina I neurones by their peripheral inputs, central conduction velocities and level of ongoing activity. 5 The discharge of Warm cells compares well with the known human psychophysics of warm sensibility, and these neurones are likely to be crucial to discriminative thermoreception. Additionally, a role in thermoregulation, a defining feature of mammalian homeostasis, is suggested.