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. 2015 Jul 28;2(3):392–405. doi: 10.1080/23328940.2015.1069437

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© 2015 The Author(s). Published with license by Taylor & Francis Group, LLC

This is an Open Access article distributed under the terms of the Creative Commons Attribution-Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. The moral rights of the named author(s) have been asserted.

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Figure 1. — Schematic model for neuronal pathways controlling cutaneous vasomotor activity. Cutaneous vasoconstrictor sympathetic premotor neurons in the medullary raphé excite cutaneous vasoconstrictor sympathetic preganglionic neurons in the spinal intermediolateral nucleus at least in part by serotonergic (5-HT) activation of 5-HT2A receptors and by glutamatergic (GLU) activation. Excitatory drive from the rostral ventrolateral medulla (RVLM) contributes to maintaining cutaneous sympathetic tone. Temperature-responsive neurons in the caudolateral preoptic region (CLPO) and rostromedial preoptic region (RMPO) provide thermoregulatory control of cutaneous vasomotor response to cold or warm stimuli. Warm-responsive preoptic neurons send direct inhibitory (GABAergic) projections to the medullary raphé. The warm-responsive neurons inhibit cutaneous sympathetic premotor neurons under warm-condition and contribute to cutaneous vasodilator response. Some of warm-responsive neurons exert inhibitory influence on cutaneous sympathetic outflow by inhibiting cutaneous vasoconstrictor neurons in the ventral tegmental area (VTA) that may provide excitatory drive to the medullary raphé neurons, or by activating cutaneous vasodilatative neurons in the rostral ventrolateral periaqueductal gray (rvlPAG) that may provide inhibitory drive the medullary raphé neurons. Cold-responsive RMPO neurons send direct excitatory (glutamatergic) projections to the medullary raphé. The cold-responsive neurons excite cutaneous sympathetic premotor neurons in the cold, and contribute to cutaneous vasoconstriction. The cold-responsive RMPO neurons receive tonic GABAergic inputs under warm-condition. PGE₂ possibly inhibits GABAergic interneurons in the RMPO that send direct projection to cold-responsive neurons in the RMPO, and elicit cutaneous vasoconstriction by reducing inhibitory influence on the medullary raphé neurons. The GABAergic interneurons may also exert inhibitory influence on the medullary raphé neurons via other indirect pathway. During aversive psychological events, cutaneous vasoconstrictor sympathetic premotor neurons in the medullary raphé are activated at least in part by excitatory drive from neurons in the amygdala, the dorsomedial hypothalamus (DMH), and orexinergic neurons in the hypothalamic area (lateral hypothalamus (LH), perifornical area (PeF) and DMH). Noradrenergic neurons in the locus coeruleus (LC) contribute to the excitatory drive via the amygdala. Activation of the neurons in the habenula elicits cutaneous vasoconstriction possibly by activation of the medullary raphé neurons. Solid black line with a question mark indicates that the pathway is not established. Solid black with dashed lines indicates that it is not known whether pathway is direct or indirect.