Abstract
This study was designed to investigate the effects of peripheral [intraperitoneal (IP)] and central [intracerebroventricular (ICV)] administration of cinnamaldehyde on concentrations of blood glucose and serum insulin in the acute hyperglycemia induced by ketamine/xylazine. Yohimbine (a α2-adrenoceptor antagonist) was used alone and in combination with cinnamaldehyde to explore the α2-adrenergic receptor contribution. A total of 48 rats were divided into eight groups with six rats in each for IP administration of normal saline, vehicle, cinnamaldehyde (25.00, 50.00 and 100 mg kg-1), yohimbine (0.50 and 2.00 mg kg-1) and cinnamaldehyde plus yohimbine. These rats were used again for ICV administration 15 days after the completion of IP experiment. During this 15 days period, the lateral ventricle of the brain was surgically cannulated for ICV administration of normal saline, vehicle, cinna-maldehyde (25.00, 50.00 and 100 µg per rat), yohimbine (5.00 and 20.00 µg per rat) and cinnamaldehyde plus yohimbine. Blood glucose levels were measured from tail blood using a glucometer and serum insulin concentrations were determined via enzyme-linked immune-sorbent assay kit. The increased levels of blood glucose and the decreased concentrations of serum insulin were significantly decreased and increased, respectively, by separate and combined IP and ICV administrations of cinnamaldehyde and yohimbine. The systemic effects of these chemical compounds were significantly greater than the central ones. Based on the results, it can be argued that cinnamaldehyde has a potential to induce anti-hyperglycemic and antihypoinsulinemic effects. Peripheral and central α2-adrenegic receptors might be involved in these effects of cinnamaldehyde.