Rat Sweat Glands Research Articles

332 New Methods for the Functional In Vitro Characterization of Isolated Human Eccrine Sweat Glands

For humans the evaporation chill through sweat secretion by eccrine sweat glands is the main mechanism for the maintenance of body temperature. In hyperhidrosis, the excess sweat formation can lead to unwanted odours that are, if not pathological, mostly prevented by reducing sweat excretion using antiperspirants. However, in vitro neither the evaluation or approval of new antiperspirants, nor basic research on sweat gland physiology can sufficiently be addressed with currently available model systems. For this very reason the development of a new functional model and assay system is of immense importance. It was thus the aim of this study to develop new methods, that enable the functional characterization of whole human eccrine sweat glands in vitro. From human skin, eccrine sweat glands were isolated enzymatically to improve yield and reproducibility. A resazurin-based vitality assay was adapted from rat sweat glands to assess vitality of human sweat glands. Furthermore, visualization of Calcium (Ca2+) currents was established, including a fluorescent Ca2+ flux assay. Using the resazurin-based assay the vitality of the isolated sweat glands now can be easily assessed and compared after isolation and treatment. Subsequently, for the first time Ca2+ currents and contractions of isolated human sweat glands were observed in vitro in the established Ca2+ flux assay. This was achieved by administration of physiological relevant stimuli that were validated by inhibition. Altogether it is now possible to assay Ca2+ currents of isolated human eccrine sweat glands. These Ca2+ currents represent a first step in the cascade that finally leads to the production of sweat. In the future the prerequisites made here could lead to a more sophisticated in vitro human sweat gland model system.

Effect of high temperature and humidity environment on rat sweat gland cells

Objective To study the effect of high temperature and humidity environment on sweat gland function and its possible mechanism. Methods Fourteen Sprague-Dawley (SD) rats were fully randomized by randomized digital tables randomly and divided into normal temperature and humidity group (control group) and high temperature and humidity group (test group) (n=7 in each group). The test group was subjected to treat by heat stress after feeding for three days. The rats were exposed to the environment of 40 ℃ and relative humidity of 65% and removed after 2 h, and the samples were taken out after 72 h. The animals in the control group were placed at room temperature without any treatment, and the samples were obtained after 72 h. Results Under the light microscope, the vacuoles of the epithelium of the sweat secretion region were decreased in the test group, and the apoptosis of cells was increased. The apoptosis index was (70.7±14.0)% in the test group, significantly higher than that in the control group [(58.6±11.7)%] (t=2.478, P=0.021). Western blotting showed that the relative expression of M3 receptor in the test group was (1.21±0.16)%, significantly higher than that in the control group [(1.81±0.41)%, t=2.711, P=0.035]. The expression of serum acetylcholine in the test group was significantly lower than that in the control group. The superoxide dismutase (SOD) activity [(13.65±5.14) U/mg] in the test group was significantly lower than that in the control group [(25.89±11.05) U/mg, t=2.633, P=0.023]. Conclusion The damage of sweat gland cells in the high temperature and humidity condition is mainly due to the decrease of tissue antioxidant. Key words: High temperature and humidity; Antioxidant; Sweat gland cell; Superoxide dismutase; M3 receptor

Wilson protein expression, copper excretion and sweat production in sweat glands of Wilson disease patients and controls

BackgroundIn Wilson disease, copper is not sufficiently excreted into bile due to the absence or malfunction of the Wilson protein copper ATPase in the excretory pathway of hepatocytes. Copper is found in sweat. It is unknown if the Wilson protein plays a role in copper excretion into sweat. It is the aim of this study to investigate Wilson protein expression in sweat glands and analysing its effects on copper excretion into sweat in controls and patients with Wilson disease.MethodsImmunofluorescent analysis of the Wilson protein in skin samples from normal rat, LEC rat and human skin biopsies were performed. Pilocarpin-induced sweat gland stimulation by iontophoretic transfer adapted from the methods used for cystic fibrosis sweat test was used for sweat induction. Sweat volume, sweat copper concentration, serum ceruloplasmin and serum copper were analysed in 28 Wilson patients and 21 controls.ResultsThe Wilson protein is expressed in human and rat sweat gland epithelia. Copper concentration in sweat is not significantly different between controls and Wilson patients. Wilson patients produce significantly smaller volumes of sweat compared to controls. Sweat production is partially reversible in Wilson patients under medical treatment for Wilson disease or after liver transplantationConclusionWilson patients show a reduced sweat production with unaltered sweat copper concentration. The Wilson protein might play an important role in physiological sweat production.

Reply to Kreier and Buijs: no sympathy for the claim of parasympathetic innervation of white adipose tissue

to the editor: Kreier and Buijs ([16][1]) have questioned our work ([14][2]) demonstrating the lack of parasympathetic nervous system (PSNS) innervation of white adipose tissue (WAT) in laboratory rats and mice, as well as in Siberian hamsters. We appreciate the opportunity to clarify and extend our

Postnatal expression and denervation induced up-regulation of aquaporin-5 protein in rat sweat gland

The evolution of aquaporin-5 (AQP5) expression during postnatal development has not been defined in the sweat gland. Previous studies have suggested that AQP isoforms in several peripheral targets are regulated by a neural mechanism. We have examined, in rat sweat glands, the expression of AQP5 during postnatal development and the effects of denervation on AQP5 expression. Both AQP5 mRNA and protein begin to be expressed at postnatal day 10, before sweat-secretory responsiveness first appears; this expression coincides with the occurrence of vasoactive intestinal peptide (VIP) immunoreactivity. Early noradrenergic and later cholinergic interaction between sweat glands and their innervation are disrupted by neonatal chemical sympathectomy or postnatal severance of the sciatic nerve. Examination of such denervated developing rats has shown that secretory responsiveness fails to arise later in the adults, and AQP5 immunostaining increases in the denervated glands, whereas gland morphogenesis and the occurrence of AQP5 expression proceed normally. Immunobloting has revealed an increase of AQP5 abundance after the denervated mature glands lose their secretory ability. These findings suggest that AQP5 protein is necessary for sweat secretion, and that the expression of AQP5 in rat sweat glands is independent of sympathetic innervation. Our data also indicate that factor(s) regulating the normal morphological development of sweat gland might be responsible for controlling AQP5 expression.

Immunohistochemical Localization of Glial Cell Line-Derived Neurotrophic Factor and Its Receptor Ret in the Rat Sweat Gland

Glial cell line-derived neurotrophic factor (GDNF) was initially identified as a neurotrophic factor for dopaminergic neurons but its effects are not restricted to nervous tissue. It is reported that GDNF-induced intercellular signaling is necessary for the normal development of a variety of non-neural tissues. In this study, immunoreactivities of both GDNF and its functional receptor Ret were evaluated in normal adult rat sweat gland by light and electron microscopy. Ret was found in the epithelial cells of the excretory duct and the coiled secretory terminal of the sweat gland. Electron microscopic observation of the secretory epithelium showed that Ret immunoreactivity is localized in the basal area of the secretory cells, facing myoepithelial cells, but it was not observed in the basal infolding or in the apical region of these cells. On the other hand, GDNF was observed in most myoepithelial cells of the coiled secretory portion of the sweat gland and in a small number of nerve fibers innervating the gland. Although the GDNF-containing nerve fibers cannot be negated as a source of the ligand for Ret in the secretory cells, the finding that GDNF and Ret are localized face to face in adjoining cells in the sweat gland implies another novel trophic role of GDNF in this tissue.

Sweat gland toxicity induced by bis (tributyltin) oxide: an ultrastructural and X-ray microanalysis study.

Acute toxicity of bis (tributyltin) oxide in the sweat glands in the rat footpad was investigated by electron microscopy and an energy-dispersive X-ray microanalyzer. Male Wistar rats received an intramuscular injection of 0.5 ml/kg bis (tributyltin) oxide. After 6-8 h, swelling of mitochondria appeared in the secretory cells of the sweat glands. After 12 h, the secretory cells began to show intracytoplasmic edema. After 16-20 h, secretory cells in some sweat glands showed marked hydropic degeneration with swollen cytoplasm. Using X-ray microanalysis, tin peaks were preferentially obtained from the swollen mitochondria of the affected secretory cells. Mitochondria dysfunction due to the toxic effects of bis (tributyltin) oxide induced changes in the secretory cells of rat sweat glands. After 24-48 h, the secretory portion of the sweat glands contained three types of cells: degenerating dark cells, regenerating cells carrying injured mitochondria, and light cells which were morphologically very similar to the cells in the transitional portion of the sweat gland. These light cells appeared to differentiate into active secretory cells after settling down in the secretory portion. Based on these observations, we concluded that the cells in the transitional portion could play an important role at least as reserve cells against secretory cell toxicity. In association with the regenerating process of the damaged secretory portions, increased mitotic activities were seen in different areas of all the dermal sweat ducts. The above-mentioned morphological observations for cell damage and subsequent regeneration and renewal ofsecretory cells in sweat gland intoxication have not been reported so far.

Differential regulation of adrenergic receptor development by sympathetic innervation

Rat sweat glands provide an interesting model system for a developmental study of adrenergic receptor expression because their sympathetic innervation undergoes a switch from a nonadrenergic to cholinergic and peptidergic phenotype. alpha 1B, alpha 2B, and beta 2 receptors are expressed in rat footpads; alpha 1 and beta 2 receptors are localized specifically to sweat glands, and alpha 2 receptors also are expressed in other tissues. alpha 1 and, to a lesser extent, beta 2 receptors decrease during development, whereas alpha 2 levels remain relatively constant. Decreased receptor expression is accompanied by the loss of alpha 1-stimulated inositol phosphate accumulation, but no change in beta-stimulated cAMP production. The number of alpha 1 and beta 2 receptors decreases after P21, when the sympathetic innervation no longer produces catecholamines. Neonatal sympathectomy causes a partial failure of alpha 1 downregulation, but has no effect on beta 2 or alpha 2 receptor levels. Therefore, at least two distinct mechanisms regulate development of adrenergic receptors in sweat glands. Innervation-independent processes control developmental expression of alpha 1, beta 2, and alpha 2 receptors, and an additional, innervation-dependent mechanism influences expression of alpha 1 receptors. Denervation at postnatal day 20, when the sympathetic innervation is cholinergic and peptidergic, results in retention of alpha 1 receptors, but cholinergic blockade begun at P20 does not. These results indicate that regulation of receptor expression in sweat glands is complex, and suggest that the innervation-dependent factors that decrease alpha 1 levels during development act through a nonadrenergic, noncholinergic mechanism.

The Role of Acetylcholine in Regulating Secretory Responsiveness in Rat Sweat Glands

While retrograde regulation of neuronal development by target-derived factors in the autonomic nervous system is well established, the importance of anterograde influences on target development is unclear. Previous studies suggest that sympathetic innervation of sweat glands plays a critical role in the acquisition and maintenance of their secretory function. To define the signal(s) responsible, we disrupted muscarinic chollnergic transmission in developing and adult rats. Treatment of young rats with the nonselective antagonist, atropine, or an antagonist selective for the glandular muscarinic subtype, 4-DAMP, delayed the development of secretory responsiveness. Treatment of adult animals with atropine caused its loss. Further, following denervation, treatment with the muscarinic agonist, pilocarpine, largely preserved responsiveness while untreated animals lost function. Thus, acetylcholine, whose presence in sweat gland innervation is retrogradely specified by developmental interactions with the target tissue, In turn plays an important role in inducing and maintaining target tissue responsiveness through muscarinic receptor activation.

Noradrenergic Regulation of Cholinergic Differentiation

When the sympathetic nerves that innervate rat sweat glands reach their targets, they are induced to switch from using norepinephrine as their neurotransmitter to acetylcholine. Catecholamines (such as norepinephrine) released by nerves growing to the sweat gland induce this phenotypic conversion by stimulating production of a cholinergic differentiation factor [sweat gland factor (SGF)] by gland cells. Here, culture of gland cells with sympathetic, but not sensory, neurons induced SGF production. Blockage of alpha 1- or beta-adrenergic receptors prevented acquisition of the cholinergic phenotype in sympathetic neurons co-cultured with sweat glands, and sweat glands from sympathectomized animals lacked SGF. Thus, reciprocal instructive interactions, mediated in part by small molecule neurotransmitters, direct the development of this synapse.

Cholinergic differentiation of rat sympathetic neurons in culture: Effects of factors applied to distal neurites

Cholinergic properties are induced in sympathetic neurons by several factors applied to entire neurons in culture. Evidence from work with the rat sweat gland model indicates that factors located in target tissues can induce cholinergic differentiation in vivo. We now report that when leukemia inhibitory factor (LIF), heart cell-conditioned medium (HCCM), or dermal fibroblast-conditioned medium (DFCM) is applied to only distal neurites in compartmented cultures of rat sympathetic neurons, the neurons exhibit an increase in specific choline acetyltransferase activity and a concomitant decrease in levels of tyrosine hydroxylase. LIF, HCCM, and DFCM also induce neurite fasciculation, thus suggesting an additional role of cholinergic switching factors in regulating axon-axon and/or axon-substrate adhesion. These results demonstrate that rat sympathetic neurons have the cellular machinery to respond to cholinergic differentiation cues located in peripheral targets, analogous to the response to nerve growth factor.

The molecular and pharmacological properties of muscarinic cholinergic receptors expressed by rat sweat glands are unaltered by denervation

Previous studies have indicated that denervation of adult rodent sweat glands results in the loss of secretory responsiveness to muscarinic agonists. To elucidate the molecular basis of this loss, we have characterized the muscarinic cholinergic receptor present in adult rat sweat glands and examined the effects of cholinergic denervation on its properties and expression. When homogenates of gland-rich tissue from adult animals were assayed with [N-methyl-3H]-scopolamine, a high-affinity muscarinic antagonist, the concentration of muscarinic receptors was 301 fmol/mg protein and the affinity was 131 pM. Autoradiographic analysis demonstrated that ligand binding sites were detectable only on glands. In competition studies with well-characterized muscarinic agents, the receptor exhibited typical muscarinic pharmacology. Further investigation with the selective muscarinic antagonists 4-diphenylacetoxy-N-methylpiperidine methiodide, pirenzepine, and AF DX-116 revealed that the sweat gland receptor belongs to the M2 glandular pharmacological subtype. In situ hybridization histochemistry with receptor subtype-specific oligonucleotide probes indicated that rat sweat glands express the m3 molecular receptor subtype. Seven days after sciatic nerve transection, when denervated glands were compared to those on the contralateral unoperated side, there was no significant difference either in the concentration or affinity of muscarinic binding sites or in receptor density or distribution. Furthermore, the molecular subtype and the level of its expression were unchanged. Thus, it appears that muscarinic binding sites and m3 receptor mRNA are present in denervated sweat glands that are unresponsive to muscarinic stimulation. These results suggest that the regulation of responsiveness occurs at a point distal to the expression of muscarinic receptors.

Developmental expression of muscarinic cholinergic receptors and coupling to phospholipase C in rat sweat glands are independent of innervation

During development, the innervation of rat sweat glands undergoes a striking change from noradrenergic to cholinergic function. The acquisition of secretory responsiveness by the glands is temporally correlated with the appearance of cholinergic properties. In addition, responsiveness fails to appear in the absence of innervation. To investigate the basis of the onset of functional transmission and secretory responsiveness and its possible relationship to innervation, we analyzed the development of muscarinic cholinergic receptors in sweat glands, examined their expression in the glands of adult rats sympathectomized at birth, and assayed the ability of muscarinic agonists to increase phosphoinositide (PI) turnover. Autoradiographic and in situ hybridization analysis revealed that muscarinic ligand binding sites were first detectable as glands begin to form on postnatal day 4 (P4). Between P4 and P14, receptor concentration increased in parallel with mRNA for the m3 receptor subtype. On P14, the concentration of ligand binding sites approached adult levels, although only a small proportion of glands at this age secrete in response to nerve stimulation or cholinergic agonists. When the pharmacological properties of muscarinic receptors in sweat glands of adult rats sympathectomized at birth were compared to those of normal glands, the concentration and affinity determined with [N-methyl-3H]-scopolamine and the Ki values determined with the subtype-selective muscarinic antagonists 4-DAMP, pirenzepine, and AF DX-116 were similar. In addition, the molecular subtype was unchanged as was the level of m3 message. Studies of PI turnover in response to muscarinic stimulation indicated that the receptors expressed in sweat glands isolated from sympathectomized and acutely denervated, as well as control, rats were functionally coupled to phospholipase C. The absence of sympathetic innervation therefore does not appear to influence either the development of muscarinic receptors or their coupling to PI turnover. Our results suggest that functional sympathetic cholinergic innervation plays a central role in the development and maintenance of secretory function at a step distal to signal transduction across the cell membrane.

Characterization of a target-derived neuronal cholinergic differentiation factor

The sympathetic innervation of rat sweat glands undergoes a target-induced switch from a noradrenergic to a cholinergic and peptidergic phenotype during development. Treatment of cultured sympathetic neurons with sweat gland extracts mimics many of the changes seen in vivo. Extracts induce choline acetyltransferase activity and vasoactive intestinal peptide expression in the neurons in a dose-dependent fashion while reducing catecholaminergic properties and neuropeptide Y. The cholinergic differentiation activity appears in developing glands of postnatal day 5 rats and is maintained in adult glands. It is a heat-labile, trypsin-sensitive, acidic protein that does not bind to heparin-agarose. Immunoprecipitation experiments with an antiserum directed against an N-terminal peptide of a cholinergic differentiation factor (CDF/LIF) from heart cells suggest that the sweat gland differentiation factor is not CDF/LIF. The sweat gland activity is a likely candidate for mediating the target-directed change in sympathetic neurotransmitter function observed in vivo.

Acquisition of cholinergic and peptidergic properties by sympathetic innervation of rat sweat glands requires interaction with normal target

The sweat glands, a target of cholinergic sympathetic neurons, were replaced with parotid gland, a target of noradrenergic sympathetic neurons, in neonatal rats. This transplantation paradigm allowed sympathetic neurons that would normally innervate the sweat glands and develop a cholinergic phenotype to innervate the parotid gland instead. The innervation of the transplanted parotid gland did not develop a cholinergic phenotype, as assessed by choline acetyltransferase activity and acetylcholinesterase immunoreactivity, but continued to express intense catecholamine fluorescence. In addition, immunoreactivity for vasoactive intestinal peptide, normally expressed by the sympathetic innervation of the sweat glands but not the parotid, was observed in only a small percentage of the parotid-associated fibers. These results suggest that cellular interactions between neurons and their targets play an important role in the differentiation of mature neurotransmitter and neuropeptide phenotypes in vivo.

Calcitonin gene-related peptide-like immunoreactive cells in the secretory portions of rat sweat glands

We found cells with calcitonin gene-related peptide-like immunoreactivity and with many cored vesicles in the secretory portions of sweat glands of rat foot pads. About 10% of sweat glands contained single immunoreactive cells. The immunoreactive cells were flask-shaped, with a narrow apex facing the glandular lumen and the bulk of the cell body in the basal half of the glandular wall. In the cytoplasm, there were many vesicles, 100-250 nm in diameter, with cores of various electron densities. These cytochemical and cytological characteristics suggest that the immunoreactive cells are homologous to gastrointestinal basal granulated cells.

Cholinergic phenotype developed by noradrenergic sympathetic neurons after innervation of a novel cholinergic target in vivo.

Mammalian sympathetic neurons in vivo may express either a noradrenergic or cholinergic phenotype. In view of the opposing effect of noradrenaline and acetylcholine on most autonomic target organs, the target-appropriate expression of neurotransmitter is critical. We have examined the maturation of the sympathetic innervation of rat sweat glands to define the developmental mechanisms regulating neurotransmitter choice in vivo. Eccrine sweat glands and their sympathetic innervation develop together postnatally in the rat. Early postnatal innervation expresses only noradrenergic properties, but as the glands and their innervation mature, noradrenergic properties decrease dramatically and cholinergic features appear in the same population of neurons. To investigate the role of the sweat gland in this change we have used a transplantation paradigm which allows sweat glands to be innervated by sympathetic neurons that would normally innervate noradrenergic target organs and remain noradrenergic throughout life. We observe that the sympathetic neurons that innervate the novel cholinergic target alter their neurotransmitter properties and develop a cholinergic phenotype. These results indicate that target organs are able to induce appropriate neurotransmitter traits in the neurons that innervate them.

Evidence for neurotransmitter plasticity in vivo: II. Immunocytochemical studies of rat sweat gland innervation during development

Previous studies of the cholinergic sympathetic innervation of rat sweat glands provide evidence for a change in neurotransmitter phenotype from noradrenergic to cholinergic during development. To define further the developmental history of cholinergic sympathetic neurons, we have used immunocytochemical techniques to examine developing and mature sweat gland innervation for the presence of the catecholamine synthetic enzymes tyrosine hydroxylase (TH) and dopamine β-hydroxylase (DBH) and for two neuropeptides present in the mature cholinergic innervation, vasoactive intestinal peptide (VIP) and calcitonin gene-related peptide (CGRP). In 7-day old animals, intensely TH- and DBH-immunoreactive axons were closely associated with the forming glands. The intensity of both the TH and DBH immunofluorescence decreased as the glands and their innervation developed. Neither TH-IR nor DBH-IR disappeared entirely; faint immunoreactivity for both enzymes was reproducibly detected in mature animals. In contrast to noradrenergic properties, the expression of peptide immunoreactivities appeared relatively late. No VIP-IR or CGRP-IR was detectable in the sweat gland innervation at 4 or 7 days. In some glands VIP-IR first appeared in axons at 10 days, and was evident in all glands by 14 days. CGRP-IR was detectable only after 14 days. In addition to VIP-IR and CGRP-IR, we examined the sweat gland innervation for several neuropeptides which have been described in noradrenergic sympathetic neurons including neuropeptide Y, somatostatin, substance P, and leu- and met-enkephalin; these peptides were not evident in either developing or mature sweat gland axons. Our observations provide further evidence for the early expression and subsequent modulation of noradrenergic properties in a population of cholinergic sympathetic neurons in vivo. In addition, the asynchronous appearance during development of the two neuropeptide immunoreactivities raises the possibility that the expression of peptide phenotypes may be controlled independently.

Development and properties of the secretory response in rat sweat glands: Relationship to the induction of cholinergic function in sweat gland innervation

Previous studies suggest that the sympathetic innervation of the sweat glands in the rat is initially noradrenergic and during development undergoes a transition in neurotransmitter phenotype to become cholinergic. To characterize this system and its development further, we have examined the adrenergic and cholinergic components of the secretory response in adult and immature rats and have studied the onset of sweating in the plantar sweat glands of developing rats. Stimulation of the sciatic nerve in adult rats elicited a secretory response which was completely blocked by the cholinergic antagonist, atropine, and was unaffected by adrenergic antagonists, indicating that nerve-evoked secretion was cholinergic. In adult rats, the sweat glands were quite sensitive to cholinergic agonists. In addition to acetylcholine, the mature sweat gland innervation contains vasoactive intestinal peptide (VIP). In some rats, the injection of VIP alone elicited a secretory response which was blocked by atropine, suggesting that the response to VIP was mediated cholinergically. In contrast to cholinergic agonists, the glands responded relatively infrequently and with reduced volumes of sweat to the α- and β-adrenergic agonists 6-fluoronorepinephrine and isoproterenol. However, when VIP, which is a potent vasodilator, was simultaneously injected with adrenergic agonists, glands in many of the injected footpads exhibited a secretory response. The response to adrenergic agonists in combination with VIP was reduced by atropine and by phentolamine plus propranolo, but was blocked completely only by a combination of the three antagonists, indicating that both adrenergic and cholinergic mechanisms were involved. In immature rats, sweating evoked by nerve stimulation first appeared at 14 days of age in 25% of the rats tested. Both the percentage of rats sweating and the number of active glands increased rapidly. At 16 days, 50% of the rats tested exhibited some active glands, and by 21 days all rats tested exhibited a secretory response. In 16-day-old rats, nerve-evoked sweating was almost completely inhibited by local injection of 1 μ M atropine, but was unaffected by phentolamine and propranolol in concentrations up to 10 μ M. Similarly, the glands were sensitive to 10 μ M muscarine, but they exhibited no secretory response to the α-adrenergic agonists, clonidine and 6-fluoronorepinephrine, nor to the β-adrenergic agonist, isoproterenol, at concentrations up to 50 μ M. The simultaneous injection of VIP with adrenergic agonists did not reveal an adrenergically mediated secretory response in 16-day-old animals. Thus, in immature as well as adult rats, the neurally evoked secretory process was mediated through a muscarinic cholinergic mechanism. The onset of nerve- and agonist-induced sweating in developing rats lagged behind the development of other cholinergic properties in the sweat glands, raising the possibility that the cholinergic responsiveness of the gland cells is induced by the release of acetylcholine from the gland innervation. Consistent with this hypothesis is the observation reported here that in adult animals in which the glands were sympathetically denervated at birth, the glands did not respond to either sciatic nerve stimulation or cholinergic agonists.

Coexistence of calcitonin gene-related peptide and vasoactive intestinal peptide in cholinergic sympathetic innervation of rat sweat glands

Immunoreactivity for calcitonin gene-related peptide (CGRP) has been localized with indirect immunofluorescence techniques in the cholinergic sympathetic fibers that innervate eccrine sweat glands in the rat. This innervation also contains vasoactive intestinal peptide-like immunoreactivity (VIP-IR). A small proportion of principal neurons in stellate and lumbar sympathetic ganglia which provide innervation to the sweat glands contain detectable CGRP-immunoreactivity. The CGRP-IR neurons are immunoreactive for VIP; however, many VIP-IR neurons in these ganglia do not contain detectable levels of CGRP-IR.