The Lovén reflex: the renaissance of a long-forgotten reflex involving autonomic and nociceptive pathways

Excerpt

The Swedish physiologist Otto Christian Lovén (1835–1904), while working in Carl Ludwig’s laboratory in Leipzig, described in rabbits an inhibitory reflex in skin generated by noxious stimulation of the skin and mediated by cutaneous vasoconstrictor neurons [16]. Lovén found that electrical stimulation of the central stump of the dorsal nerve of the hind paw, a branch of the superficial peroneal nerve (the nervus dorsalis pedis, a skin nerve), results in (1) ipsilateral saphenous artery vasodilatation; (2) no vasodilation but sometimes vasoconstriction in the ear lobe; and, (3) systemic vasoconstriction causing an increase in blood pressure. Conversely, stimulation of the central stump of the posterior branch of the auricular nerve results in (1) vasodilation in the ipsilateral ear lobe; (2) no vasodilation but sometimes vasoconstriction of the saphenous artery; and, (3) systemic vasoconstriction causing an increase in blood pressure. Lovén concluded that vasomotor fibers innervating the saphenous artery or ear blood vessels must be different from the vasomotor fibers responsible for the increase in systemic blood pressure and that vasodilation of skin vessels is generated reflexly by stimulation of afferents which innervate the same skin territory that is innervated by the cutaneous vasomotor fibers or a close-by territory. Lovén did not comment on his results as being generated by decreased activity in vasoconstrictor neurons or activation of vasodilator neurons; the details of the concept of nerve-mediated vasoconstriction and vasodilation developed much later. Lovén’s observation went into the literature as the “Lovén reflex.” …