Galanin-immunoreactive nerves in the mouse and rat pancreas

Abstract

Galanin-containing nerve fibers have previously been observed in the human, dog, and pig pancreas. Whether the mouse and rat pancreas also contain galanin nerve fibers has been a matter of debate. Therefore, we examined the distribution of galanin in the mouse and the rat pancreas. Further, the possible localization of galanin to adrenergic nerves was studied using sequential immunostaining for galanin and tyrosine hydroxylase (TH). In the mouse pancreas, numerous galanin-immunoreactive (GIR) nerve fibers occurred around blood vessels. They were less numerous in the exocrine parenchyma and in association with the islets. In contrast, in the rat pancreas, only a few GIR nerves were found. They were located around blood vessels and scattered in the exocrine parenchyma. Occasionally, GIR nerves were also observed in the islets. There was a dense distribution of TH-immunoreactive fibers in both the mouse and the rat pancreas. Sequential immunostaining revealed co-localization of galanin and TH immunoreactivity in nerve fibers in both the mouse and the rat pancreas. Following chemical sympathectomy using 6-hydroxydopamine (6-OHDA), not all GIR nerves disappeared. In the mouse pancreas a remaining population of galanin nerves was found around blood vessels, and occasionally in the islets. In the rat pancreas, a few GIR nerves were seen also after chemical sympathectomy. We conclude that intrapancreatic GIR nerves also occur in the mouse and the rat. These findings suggest that many of the GIR nerves are adrenergic but that non-adrenergic, possibly intrinsic or sensory GIR nerves exist as well in both the mouse and the rat pancreas.

Galanin-like Immunoreactive Neural Elements in Domestic Ruminant Pancreas.

“…The localization of galanin-like immunoreactivity in the neural elements of the pancreas of cattle, sheep and goat is consistent with those in other mammalian species such as pig [14,16], dog [5,14,23], cat [6], rat and mouse [13], baboon [23] and human [1,14,19]. However, topographical distribution pattern and frequency of occurrence of the Gal-IR neural elements in the pancreas varied not only among the ruminants but also with those of the other species.…”

“…In the dog, however, the opposite has been observed, i.e., dense innervation by the Gal-IR nerve fibers in the endocrine pancreas and minimal in the exocrine pancreas [5,14,23]. Moreover, the Gal-IR nerve fibers in mouse and rat have shown minimal frequency of distribution both in the exocrine and endocrine pancreas [13]. The present findings on the appreciable innervation by Gal-IR nerve fibers in the acini, excretory ducts and blood vessels of the exocrine pancreas may suggest that galanin is a key peptide influencing the ruminant pancreatic exocrine function such as regulation of the exocrine secretion, modulation of the excretory duct activity and control of vasomotor functions.…”

“…Immunohistochemical studies have demonstrated galanin in the neural elements of the pancreas of several mammalian species such as pig [14,16], dog [5,14,23], cat [6], rat and mouse [13], baboon [23] and human [1,14,19]. Recently, we have reported striking findings on the presence of galanin-like immunoreactivity not only in the neural elements but also in the endocrine cells of the large islets of cattle, a large ruminant species [2,17].…”

Leptin increases circulating glucose, insulin and glucagon via sympathetic neural activation in fasted mice

“…Although in this study, we did not perform tissue catecholamine measurements or histology for sympathetic nerves in the mice, 6-OHDA at the same dose level (40 mgakg) produces marked reductions of tissue noradrenaline and decreases the number of tyrosine hydroxylase containing nerves. 18,19 Furthermore, 6-OHDA is known to produce a selective chemical sympathectomy at the level of post-ganglionic nerve terminals and does not affect the adrenal medulla. 17,18,19 Therefore, our results suggest that intact sympathetic innervation is required for the gluco-regulatory actions of leptin during fasting.…”

“…17 Pancreatic islets of mice treated with 6-OHDA are devoid of sympathetic innervation at 48 h after administration of 6-OHDA as evident by ¯uorescent demonstration of catecholamines 18 and immunohistochemical visualization of the noradrenergic nerve marker, tyrosine hydroxylase. 19 …”