The neuropeptide PACAP contributes to the glucagon response to insulin-induced hypoglycaemia in mice.
The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide in the autonomic nerves innervating the pancreatic islets and previous studies have shown that it stimulates insulin and glucagon secretion. It is known that autonomic nerve activation contributes to the glucagon response to hypoglycaemia. In the present study, we evaluated whether PACAP is involved in this glucagon response by examining the glucagon response to insulin-induced hypoglycaemia in mice genetically deleted of the specific PACAP receptor, the PAC1 receptor. We found that insulin (1 U kg-1 ip) reduced circulating glucose to a hypoglycaemic level of approximately 2.5 mmol L-1 in PAC1R-/- mice and their wild-type counterparts with no difference between the groups. However, the glucagon response to this hypoglycaemia was markedly impaired in the PAC1R-/- mice. Thus, after 120 min, plasma glucagon was 437 +/- 79 ng L-1 in wild-type mice vs. only 140 +/- 36 ng L-1 in PAC1R-/- mice (P=0.004). In contrast, the glucagon response to intravenously administered arginine (0.25 g kg-1) was the same in the two groups of mice. We conclude that PACAP through activation of PAC1 receptors contribute to the glucagon response to insulin-induced hypoglycaemia. Therefore, the glucagon response to hypoglycaemia is dependent not only on the classical neurotransmitters but also on the neuropeptide PACAP.
Persson
K
K
Department of Medicine, Lund University, Lund, Sweden.
Ahrén
B
B
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001786:Blood Glucose / Q000187:drug effects; D005260:Female; D005934:Glucagon / Q000097:blood* / Q000378:metabolism; D007003:Hypoglycemia / Q000139:chemically induced / Q000378:metabolism*; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009479:Neuropeptides / Q000378:metabolism*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D011979:Receptors, Pituitary Hormone / Q000235:genetics*
C495402:Adcyap1 protein, mouse; C495504:Adcyap1r1 protein, mouse; D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D009479:Neuropeptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D011979:Receptors, Pituitary Hormone; D005934:Glucagon; D001120:Arginine