Effect of nadolol injected prior to CRH on stress-induced plasma corticosterone level in rat

The proposed research is the part of our investigation of the role of catecholamines in the alterations provoked by stress. Especially, we elucidate if Nadolol injected prior to CRH ICV has some effect on plasma corticosterone level. 15 mg/kg of Nadolol (the dose sufficient to prevent CRH-induced increases in heart-rate for 2 hr), dissolved in saline was administered intraperitoneally, 30 minutes prior to CRH (The dose of interest for CRH - 1 mkg/kg - was determined earlier, as provoking the maximal increase of plasma corticosterone level after 20 minutes of its ICV injection). Whole blood was collected at 11.00 am, via indwelling jugular catheter at 0 (control) and 15 minutes after Nadolol injection, also 30 and 60 min after CRH injection. After centrifugation the plasma level of corticosterone was essayed using ELISA method. 15 minutes after Nadolol injection the level of plasma corticosterone in comparing with control wasn't changed, at subsequent time-points plasma corticosterone level was increased but significant difference was observed only after 30 minutes. Thus, according our results, 30 min after injection, the dose of Nadolol, sufficient to prevent CRH-induced increase in heart rate, doesn't preclude the CRH-induced increase of plasma corticosterone - one of key signs of the stress-axis activation. The results were discussed.