Neural mechanisms of thermo-regulation : Identification of the cutaneous vasomotor center

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Neural mechanisms of thermo-regulation, especially the pathway from so called thermo-regulatory center of the hypothalamus to the cutaneous vasoconstrictor fibers has been poorly understood. The ear of the rabbit is one of the thermo-regulatory organ, controlling its blood flow. We previously proposed that the reticulo-spinal neurons (Cu neurons) in the rostral ventral medulla that excited by the electrical stimulation of the dorso-medial hypothalamus were premotor neurons for cutaneous vasoconstrictor fibers of the ear (Kishi, et al., 1999). In the present project, we simultaneously recorded activities of the ear sympathetic vasoconstrictor fibers and the reticulo-spinal neurons in the rostral ventral medulla and analyzed their spontaneous activity in the point of view of their rhythmic activities.Cu neurons and cutaneous vasoconstrictor fibers of the ear had not cardiac cycle-related rhythmic activity, but renal sympathetic nerve shown clear cardiac cycle-related rhythmic activity. Both Cu neurons and cutaneous vasoconstrictor fibers had respiration-related activity. The degree of modulation of the respiratory-related fluctuation of the activity of the Cu neuron was almost same as that of cutaneous vasoconstrictor fibers.The responsiveness to the stimulation of the dorso-medial hypothalamus and the spontaneous activity of the Cu neurons indicated that these Cu neurons were premotor neurons for the cutaneous vasoconstrictor fibers.