Yamazato M, Sakima A, Nakazato J, Sesoko S, Muratani H, Fukiyama K
Third Department of Internal Medicine, University of the Ryukyus School of Medicine, 207 Uehara, Okinawa 903-0215, Japan.
Am J Physiol Regul Integr Comp Physiol. 2001 Dec;281(6):R1868-76. doi: 10.1152/ajpregu.2001.281.6.R1868.
We examined the effects of clonidine injected unilaterally into the rostral ventrolateral medulla (RVLM) of conscious, unrestrained rats. We also examined whether the local alpha(2)-adrenoceptor mechanism contributed to the action of clonidine injected into the RVLM. Injection of clonidine but not vehicle solution significantly decreased the mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) in conscious, unrestrained rats as well as in propofol-anesthetized rats. The frequency of natural behavior was significantly lower after clonidine injection than after vehicle injection. The depressor and sympathoinhibitory responses were significantly larger in the propofol-anesthetized rats than in the conscious rats. Coinjection of a selective alpha(2)-adrenoceptor antagonist, 2-methoxyidazoxan, with clonidine into the RVLM significantly attenuated the depressor, bradycardiac, sympathoinhibitory, and sedative effects of clonidine injected alone. In conclusion, clonidine injected into the RVLM decreased MAP, HR, and RSNA and caused sedation in conscious, unrestrained rats. The action of clonidine in the RVLM was at least partly mediated by alpha(2)-adrenoceptor mechanisms.
我们研究了向清醒、自由活动的大鼠延髓头端腹外侧区（RVLM）单侧注射可乐定的作用。我们还研究了局部α₂ -肾上腺素能受体机制是否参与了向RVLM注射可乐定的作用。向清醒、自由活动的大鼠以及丙泊酚麻醉的大鼠注射可乐定而非溶媒，显著降低了平均动脉压（MAP）、心率（HR）和肾交感神经活动（RSNA）。注射可乐定后自然行为的频率显著低于注射溶媒后。丙泊酚麻醉的大鼠的降压和交感抑制反应显著大于清醒大鼠。将选择性α₂ -肾上腺素能受体拮抗剂2-甲氧基咪唑克生与可乐定共同注射到RVLM中，可显著减弱单独注射可乐定的降压、减慢心率、交感抑制和镇静作用。总之，向RVLM注射可乐定可降低清醒、自由活动大鼠的MAP、HR和RSNA并引起镇静。可乐定在RVLM中的作用至少部分由α₂ -肾上腺素能受体机制介导。
