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Insulin‐responsive autonomic neurons in rat medulla oblongata
Author(s) -
Senthilkumaran M.,
Bobrovskaya L.,
Verberne A. J. M.,
LlewellynSmith I. J.
Publication year - 2018
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.24523
Subject(s) - endocrinology , medicine , dorsal motor nucleus , adrenergic neurons , choline acetyltransferase , medulla oblongata , phenylethanolamine n methyltransferase , area postrema , insulin , medulla , catecholaminergic cell groups , hypoglossal nucleus , phenylethanolamine , biology , cholinergic neuron , brainstem , chemistry , cholinergic , vagus nerve , catecholamine , adrenergic , central nervous system , dopamine , tyrosine hydroxylase , catecholaminergic , stimulation , receptor
Abstract Low blood glucose activates brainstem adrenergic and cholinergic neurons, driving adrenaline secretion from the adrenal medulla and glucagon release from the pancreas. Despite their roles in maintaining glucose homeostasis, the distributions of insulin‐responsive adrenergic and cholinergic neurons in the medulla are unknown. We fasted rats overnight and gave them insulin (10 U/kg i.p.) or saline after 2 weeks of handling. Blood samples were collected before injection and before perfusion at 90 min. We immunoperoxidase‐stained transverse sections of perfused medulla to show Fos plus either phenylethanolamine N ‐methyltransferase (PNMT) or choline acetyltransferase (ChAT). Insulin injection lowered blood glucose from 4.9 ± 0.3 mmol/L to 1.7 ± 0.2 mmol/L (mean ± SEM ; n = 6); saline injection had no effect. In insulin‐treated rats, many PNMT‐immunoreactive C1 neurons had Fos‐immunoreactive nuclei, with the proportion of activated neurons being highest in the caudal part of the C1 column. In the rostral ventrolateral medulla, 33.3% ± 1.4% ( n = 8) of C1 neurons were Fos‐positive. Insulin also induced Fos in 47.2% ± 2.0% ( n = 5) of dorsal medullary C3 neurons and in some C2 neurons. In the dorsal motor nucleus of the vagus (DMV), insulin evoked Fos in many ChAT‐positive neurons. Activated neurons were concentrated in the medial and middle regions of the DMV beneath and just rostral to the area postrema. In control rats, very few C1, C2, or C3 neurons and no DMV neurons were Fos‐positive. The high numbers of PNMT‐immunoreactive and ChAT‐immunoreactive neurons that express Fos after insulin treatment reinforce the importance of these neurons in the central response to a decrease in glucose bioavailability.