| Abstrakt: |
Introduction: The presence of opioid receptors in the cuneiform nucleus (CnF), located in the mesencephalic area, and their involvement in the central cardiovascular responses have been shown. Therefore, this study is designed to examine the possible role of mu- (µ) and delta- (δ) opioid receptors in the CnF in the cardiovascular responses in normotensive and hemorrhagic hypotensive rats. Methods and Materials: Following anesthesia and the recording of the blood pressure, the agonist and antagonist of µ- (morphine and naloxone) and δ- (D-Pen 2, 5-Enkephalin hydrate (DPDPE) and naltrexone) receptors were microinjected into the CnF. In the hemorrhagic groups, the drugs were microinjected into the nucleus 2 min after withdrawing 15% of the total blood volume (TBV). Time-course changes (∆) in the mean arterial pressure (MAP), systolic blood pressure (SBP), and heart rate (HR) were obtained and compared with the control and hemorrhage groups. Results: Microinjecting morphine in both normotensive and hemorrhagic rats significantly decreased ∆SBP, ∆MAP, and ∆HR; also, naloxone significantly increased all these parameters. The cardiovascular effects of DPDPE and naltrexone were not significant in the normotensive rats; however, DPDPE attenuated only the tachycardia induced by the hypotensive hemorrhage. Conclusion: The findings of this study revealed that the opioid receptors in the CnF had an inhibitory effect on the cardiovascular parameters in both normotensive and hypotensive hemorrhagic conditions and these effects were mostly mediated by µ-opioid receptors. [ABSTRACT FROM AUTHOR] |
