Sympathetically induced changes in the responses of guard hair and type II receptors in the cat.

Abstract

SUMMARY1. Sympathetic effects on the activity of single guard hair receptors and slowly adapting, type II mechanoreceptors were studied in anaesthetized cats.2. Spontaneous activity in type II receptors and mechanically evoked activity in both type II and guard hair receptors was recorded both without and with electrical stimulation of the lumbar sympathetic trunk.3. Almost all guard hair receptors were desensitized by sympathetic stimulation, the mean effect being an increase in threshold to 2-2 times the unconditioned value.4. One third of the more slowly adapting guard hair units showed sympathetically induced spontaneous activity.5. These sympathetic effects on guard hair receptors appear not to be related to pilomotor responses or to changes in central arterial pressure.6. Individual type HI receptors were found to be excited by skin stretch along one of two axes: either parallel or perpendicular to the long axis of the leg. Intermediate orientations were not observed.7. 'Perpendicular' units showed marked increases in resting discharge but no change in mechanical sensitivity during sympathetic stimulation. 'Parallel' units were unaffected.8. The sympathetic effect appeared not to be related to changes in blood pressure or skin tension.9. It is suggested that the location and orientation of stretch sensitivity of these receptors make them well suited for detection of limb movements; however, no satisfactory functional explanation was found for the pronounced sympathetic facilitation of only one subset of the receptors.

Unmyelinated innervation of sinus hair follicles in rats

“…In the light of the present results the question of whether the sympathetic inhibition could be due to indirect effects on blood flow or skin compliance must be considered. Depression of responses of guard and down hair units by sympathetic stimulation has also been described in the rabbit ear (Barasi and Lynn 1986) and the cat hind limb (Pierce and Roberts 1981). These studies concluded that sympathetic effects were unlikely to be due to indirect changes in blood flow.…”

Regeneration of Unmyelinated Axons After Injury of Mammalian Peripheral Nerve

“…There may be other classes of postganglionic sympathetic neurone supplying skin that have yet to be characterized. For example, there is evidence that activity in sympathetic fibres can cause modulation of the sensitivity of cutaneous receptors by a mechanism other than altering the local blood flow (Pierce & Roberts, 1981;Roberts, Elardo & King, 1985;Barasi & Lynn, 1986; but also note Shea & Perl, 1985c): the physiological significance of these effects is a matter of some doubt (for fuller discussions see Janig, 1985bJanig, , 1989.…”

Sympathetic modulation of cold‐receptive neurones in the trigeminal system of the rat.

“…In general all the experiments using amphibian or in vitro mammalian preparations have reported purely excitatory responses to sympathetic stimulation or superfused noradrenaline (Loewenstein, 1956;Loewenstein & Altamirano-Orrego, 1956;Chernetski, 1964;Spray, 1974; Schiff, 1974;Calof, Jones & Roberts, 1981). In contrast, those using in vivo mammalian preparations have reported either mixed responses (Hunt, 1960;Eldred, Schnitzlein & Buchwald, 1960;Edwall & Scott, 197 1 ;Freeman & Rowe, 1981;Pierce & Roberts, 1981;Roberts & Levitt, 1982;Barasi & Lynn, 1983), or suppressive responses (Nilsson, 1972;Cash & Linden, 1982;Barasi & Lynn, 1983;Passatori & Filippi, 1983).…”