The role of the vagal innervation of the gut in insulin release in
lactating ewes
C.B. Herath, G.W. Reynolds, D.D.S. Mackenzie, S.R. Davis and P.M.
Harris
Department of Animal Science, Massey University, Palmerston North,
New Zealand.
Proceedings of the New Zealand Society of Animal Production, 1996,
56: 110-113
The vagal innervation of the pancreas and upper gastrointestinal tract
has been implicated in the release of insulin in response to hyperglycaemia
in several mammalian species. Therefore the role of the vagal innervation of
the abomasum and upper small intestine in the release of insulin and its
effect on glucose metabolism was studied in lactating ewes because of the
importance of glucose for milk synthesis and secretion in ruminants. Vagal
fibres innervating the abomasum, pylorus and duodenum were sectioned in
3 lactating ewes (VAG); 3 control lactating ewes underwent sham-
operations (SHAM). Seven and 14 days after the surgery, all animals were
given an intravenous injection of glucose (100 mg/kg BW) and jugular
blood samples collected for glucose and insulin determinations. Plasma
glucose concentration (mean ± standard error) rose in the VAG group from a
pre-injection level of 3.9 ± 0.2 mmol/L to 6.2 ± 0.2 mmol/L and in the
SHAM group from 3.7 ± 0.2 mmol/L to 6.3 ± 0.2 mmol/L. Maximum
glucose concentration occurred at 5 minutes post-injection in both groups
but declined more slowly in the VAG group than in the SHAM group and
were significantly (P < 0.05) different at both 45 and 60 minutes post-
injection. This resulted in a larger total area under the curve for the VAG
group (P < 0.01) compared to the SHAM group. In the SHAM group,
plasma insulin concentration rose from 685 ± 193 pg/mL to 3462 ± 649
pg/mL in response to the injection of glucose, whereas in the VAG group,
plasma insulin response was smaller and reached a peak of 1530 ± 649
pg/mL from a basal level of 615 ± 193 pg/mL. The mean plasma insulin
concentration after glucose injection in the VAG group was significantly (P
< 0.05) lower than that for the SHAM group at both 5 and 10 minutes post-
injection. These results indicate that vagal innervation of the stomach
(abomasum), and duodenum modifies the pancreatic release of insulin in
response to hyperglycaemia induced by intravenous glucose administration.
Keywords: NZSAPAB;
lactating ewe; vagus; glucose; insulin.
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Last Updated 18-03-1997
