Central beta-adrenoceptor involvement in neural control of blood glucose in pigeons.
The effects of ICV injections of adrenaline (30 nmol in 1 microL of saline) on blood glucose levels were investigated in conscious adult pigeons. This procedure increased blood glucose levels at 15-45 min after treatment. Previous ICV injection of propranolol (50 nmol) suppressed the increase observed at 15 min. The higher propranolol dose (100 nmol) was more effective than the lower dose (50 nmol) at blocking adrenaline-induced hyperglycemia. On the other hand, the ICV pretreatment with an alpha-adrenergic antagonist, phentolamine, slightly potentiated the hyperglycemia caused by ICV injection of adrenaline. The IP administration of propranolol (100 nmol) or phentolamine (100 nmol) before adrenaline ICV failed to induce change in the hyperglycemic response induced by this catecholamine. Both IP and ICV injections of these adrenergic blockers, before ICV injections of saline, evoked no changes in baseline glycemic levels. Therefore, elevation of blood glucose concentration by ICV adrenaline and blockade of the response by propranolol suggest the involvement of a central beta-adrenergic mechanism in the neural control of glycemia in pigeons.
Souza
W F
WF
Department of Physiological Sciences-CCB, Federal University of Santa Catarina, Florianópolis, Brazil.
Freitas
C G
CG
Marino-Neto
J
J
Paschoalini
M A
MA
D000818:Animals; D001786:Blood Glucose / Q000187:drug effects*; D010856:Columbidae; D004837:Epinephrine / Q000494:pharmacology*; D005260:Female; D007278:Injections, Spinal; D008297:Male; D011433:Propranolol / Q000494:pharmacology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*
D001786:Blood Glucose; D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D004837:Epinephrine