Activation of imidazoline receptor by agmatine to lower plasma glucose in streptozotocin-induced diabetic rats.
In the present study, we use agmatine, an endogenous ligand, to investigate the role of imidazoline receptor in plasma glucose regulation in streptozotocin-induced diabetic rats (STZ-diabetic rats). After injection into the central lateral ventral (i.c.v.) of fasting STZ-diabetic rats for 30 min, agmatine produced plasma glucose lowering action in a concentration-dependent manner without alteration the mean arterial pressure (MAP). However, the plasma glucose was markedly raised in STZ-diabetic rats receiving similar injection of clonidine at dose (1 micromol/rat, i.c.v.) sufficient to lower MAP. Mediation of alpha(2)-adrenoceptor in this action of agmatine seems unlikely. The plasma glucose lowering action of agmatine (1 micromol/rat, i.c.v.) was abolished by the pretreatment with BU-224 at concentration (100 nmol/rat) sufficient to block cerebral I(2)-imidazoline receptors. Also, this action of agmatine in STZ-diabetic rats disappeared by spinal cord truncation between C6 and C7. Activation of cerebral I(2)-imidazoline receptor by agmatine can thus be considered for the lowering of plasma glucose. In conclusion, we suggest that an activation of I(2)-imidazoline receptors in the brain may lower plasma glucose without insulin in animal.
Jou
Shuo-Bin
SB
Department of Neurology, School of Medicine and Hospital, China Medical University, Taichung City, Taiwan.
Liu
I-Min
IM
Cheng
Juei-Tang
JT
D000376:Agmatine / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D001786:Blood Glucose / Q000187:drug effects* / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000097:blood* / Q000188:drug therapy; D004305:Dose-Response Relationship, Drug; D054755:Imidazoline Receptors; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D011955:Receptors, Drug / Q000378:metabolism*
D001786:Blood Glucose; D054755:Imidazoline Receptors; D011955:Receptors, Drug; D000376:Agmatine