De Castro M G, Foscolo R B, Reis A M, Coimbra C C
Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Brazil.
Physiol Behav. 1997 Feb;61(2):215-20. doi: 10.1016/s0031-9384(96)00362-9.
The effect of norepinephrine (NE) injection into the medial preoptic area (MPOA) on plasma glucose was studied in freely moving male rats. The rats were implanted with chronic jugular catheters for blood sampling and with unilateral intracerebral cannulas placed just above the MPOA. Blood samples were taken immediately before and 5, 10, 15, and 30 min after NE injection. As early as 5 min after NE injection, plasma glucose levels rose rapidly, reaching a peak at 15 min poststimulus. The hyperglycemic response to NE injection into the MPOA was dose-related within the range of doses tested (10, 20, and 40 nmol). Previous administration of phentolamine (50 nmol), but not propranolol (100 nmol), into the MPOA blocked the hyperglycemic response to NE injection into the MPOA. The increase of plasma glucose induced by NE into the MPOA and the blockade of the hyperglycemic response to NE by phentolamine suggest the involvement of an alpha-adrenergic mechanism in MPOA-mediated hyperglycemia. On the basis of these and previous results, we propose that MPOA alpha-adrenergic synapses relay impulses activating the sympathetic outflow expressed by neurally mediated hyperglycemia.
在自由活动的雄性大鼠中研究了向内侧视前区（MPOA）注射去甲肾上腺素（NE）对血糖的影响。给大鼠植入用于采血的慢性颈静脉导管，并在MPOA上方植入单侧脑内插管。在注射NE前以及注射后5、10、15和30分钟立即采集血样。早在注射NE后5分钟，血糖水平迅速升高，在刺激后15分钟达到峰值。在测试剂量范围（10、20和40 nmol）内，向MPOA注射NE引起的高血糖反应与剂量相关。先前向MPOA注射酚妥拉明（50 nmol）而非普萘洛尔（100 nmol）可阻断向MPOA注射NE后的高血糖反应。NE注入MPOA诱导的血糖升高以及酚妥拉明对NE高血糖反应的阻断表明α-肾上腺素能机制参与了MPOA介导的高血糖症。基于这些及先前的结果，我们提出MPOAα-肾上腺素能突触传递激活由神经介导的高血糖症所表达的交感神经输出的冲动。
