Lima L, Arce V, Tresguerres J A, Devesa J
Laboratorio de Neurociencia Ramón Domínguez, Department of Physiology, School of Medicine Santiago de Compostela, Spain.
Life Sci. 1993;53(8):665-8. doi: 10.1016/0024-3205(93)90277-a.
This study was undertaken to investigate whether or not alpha 2-adrenergic pathways would negatively modulate the hypothalamic somatostatin release in rats. To induce pharmacological changes in SS release, three groups of male Sprague-Dawley rats (n = 30/group) were separately anesthetized by ip administration of urethan (which increases SS tone; 1.2 g/kg), pentothal (which impairs SS release; 30 mg/kg), or ketamine (which does not affect spontaneous SS secretion; 40 mg/kg). Ten rats from each group were challenged with GRF (2 micrograms/kg iv), clonidine (40 micrograms/kg iv), or GRF plus clonidine. Administration of clonidine markedly increased the GH responsiveness to GRF in rats anesthetized with urethane or ketamine. In contrast, the GH response to GRF was not modified by clonidine in rats anesthetized with pentothal. These results show that alpha 2-adrenergic stimulation only modifies the GRF-induced GH rise when SS release is high. Therefore, in rats, central alpha 2-adrenergic pathways appear to play a main inhibitory effect on hypothalamic SS secretion.
本研究旨在探讨α2-肾上腺素能通路是否会对大鼠下丘脑生长抑素的释放产生负调节作用。为诱导生长抑素释放的药理学变化，将三组雄性Sprague-Dawley大鼠（每组n = 30）分别通过腹腔注射乌拉坦（增加生长抑素水平；1.2 g/kg）、硫喷妥钠（损害生长抑素释放；30 mg/kg）或氯胺酮（不影响自发性生长抑素分泌；40 mg/kg）进行麻醉。每组选取10只大鼠，分别用生长激素释放因子（GRF，2微克/千克静脉注射）、可乐定（40微克/千克静脉注射）或生长激素释放因子加可乐定进行刺激。在乌拉坦或氯胺酮麻醉的大鼠中，给予可乐定可显著增强生长激素对生长激素释放因子的反应性。相比之下，在硫喷妥钠麻醉的大鼠中，可乐定对生长激素释放因子引起的生长激素反应无影响。这些结果表明，仅当生长抑素释放较高时，α2-肾上腺素能刺激才会改变生长激素释放因子诱导的生长激素升高。因此，在大鼠中，中枢α2-肾上腺素能通路似乎对下丘脑生长抑素分泌起主要抑制作用。
