Development of choline acetyltransferase (CAT) in the sympathetic innervation of rat sweat glands

Abstract

It has been postulated that the developing sympathetic innervation of rat eccrine sweat glands changes from adrenergic to cholinergic under the influence of its target. In agreement with previous evidence that the sympathetic innervation of adult rat sweat glands is cholinergic, we found that choline acetyltransferase (CAT)-immunoreactive nerve fibers are present in adult glands, and that gland-rich chunks of adult footpads contain CAT enzyme activity. We were therefore interested in determining when CAT activity is first expressed in the developing gland innervation. Low levels of acetylating activity were observed in rat footpads as early as postnatal day 4, when sympathetic fibers first contact the glands. A greater than fourfold increase in CAT specific activity occurred between postnatal days 11 and 21. Neonatal treatment of rats with the adrenergic neurotoxin 6-hydroxydopamine (6-OHDA) eliminated most of the CAT activity in 14 and 19 d footpads. In contrast, the acetylating activity observed prior to day 11 was unaffected by neonatal 6-OHDA treatment, and only slightly reduced by the selective CAT inhibitor, naphthylvinylpyridine. These results indicate that the sympathetic fibers that innervate rat sweat glands do not acquire detectable levels of CAT activity until a full week after they contact the glands.

Heat Acclimatization in Hot Summer for Ten Weeks Suppress the Sensitivity of Sweating in Response to Iontophoretically-administered Acetylcholine

“…The sympathetic innervation of sweat glands is unusual in that the postganglionic fibers release ACh rather than norepinephrine, the transmitter found at other sympathetic synapses. ACh is also necessary for the development and maintenance of secretory responsiveness (Leblanc & Landis, 1986;Weihe et al, 1996). Sweat gland innervation also contains choline acetyltransferase, the synthetic enzyme for ACh, and the vesicular ACh transporter, but not catecholamines (Leblanc & Landis, 1986;Weihe et al, 1996).…”

“…ACh is also necessary for the development and maintenance of secretory responsiveness (Leblanc & Landis, 1986;Weihe et al, 1996). Sweat gland innervation also contains choline acetyltransferase, the synthetic enzyme for ACh, and the vesicular ACh transporter, but not catecholamines (Leblanc & Landis, 1986;Weihe et al, 1996). Furthermore, muscarinic agonists mimic the ability of nerve stimulation to elicit sweating, and nerve-evoked sweating can be blocked by muscarinic antagonists (Vilches et al, 1995).…”

Catecholamines Are Required for the Acquisition of Secretory Responsiveness by Sweat Glands

“…The gland innervation contains choline acetyltransferase (ChAT), the synthetic enzyme for acetylcholine, and the vesicular acetylcholine transporter (VAChT) but not catecholamines (Landis and Keefe, 1983;Leblanc and Landis, 1986;Weihe et al, 1996). Muscarinic agonists mimic the ability of nerve stimulation to elicit sweating, and nerve-evoked sweating is blocked by muscarinic antagonists (Langley, 1922;Hayashi and Nakagawa, 1963;Stevens and Landis, 1987;Vilches et al, 1995).…”

Norepinephrine Facilitates the Development of the Murine Sweat Response But Is Not Essential

“…6 A,B). The switch from a noradrenergic to cholinergic phenotype in rats is associated with a downregulation of TH immunoreactivity and the appearance of ChAT and the neuropeptides VIP and CGRP (Leblanc and Landis, 1986;Landis et al, 1988;Stevens and Landis, 1988). To characterize the neuronal switch in mice, we performed immunocytochemistry on foot pads from mice at various ages.…”

“…The sympathetic neurons that initially make contact with the developing sweat glands at P4 are noradrenergic: they express tyrosine hydroxylase (TH) and dopamine ␤-hydroxylase (DBH) and produce norepinephrine (NE) (Landis and Keefe, 1983). Beginning at about postnatal day (P) 11 and continuing to P21, however, there is a gradual loss of these noradrenergic markers and the acquisition of the cholinergic markers choline acetyltransferase and acetylcholinesterase, as well as the neuropeptides, vasoactive intestinal peptide (VIP), and calcitonin gene-related peptide (Landis and Keefe, 1983;Leblanc and Landis, 1986;Stevens and Landis, 1987;Landis et al, 1988). Sweating in the adult (P21 and older) is elicited by cholinergic agonists and blocked by cholinergic antagonists.…”