Rose J D, Marrs G S, Moore F L
Department of Psychology, University of Wyoming, Laramie, Wyoming 82071, USA.
Horm Behav. 1998 Dec;34(3):268-82. doi: 10.1006/hbeh.1998.1483.
Endogenously secreted or injected corticosterone (CORT) rapidly suppresses courtship clasping in male roughskin newts (Taricha granulosa) by an action on a specific neuronal membrane receptor. Previous studies, using immobilized newts, showed that CORT administration rapidly depresses excitability of reticulospinal neurons and attenuates medullary neuronal responsiveness to clasp-triggering sensory stimuli. The present study used freely moving newts to examine clasping responses and concurrently record sensorimotor properties of 67 antidromically identified reticulospinal and other medullary reticular neurons before and after CORT injection. Before CORT, reticulospinal neurons fired in close association with onset and offset of clasps elicited by cloacal pressure. Reticulospinal neurons also showed firing correlates of nonclasping motor events, especially locomotion. Neuronal activity was typically reduced during clasping and elevated during locomotion. Medullary neurons that were not antidromically invaded (unidentified neurons) usually showed sensorimotor properties that resembled those of reticulospinal neurons. Intraperitoneal CORT (but not vehicle) reduced the probability and quality of hindlimb clasping in response to cloacal pressure, especially within 5-25 min of injection. Simultaneously, responses of reticulospinal and unidentified neurons to cloacal pressure and occurrence of clasping-related activity were attenuated or eliminated. CORT effects were relatively selective, altering clasping-related neuronal activity more strongly than activity associated with nonclasping motor events. The properties of CORT effects indicate that the hormone impairs clasping by depressing processing of clasp-triggering afferent activity and by disrupting the medullary control of clasping normally mediated by reticulospinal neurons. The rapid onset of these CORT effects implicates a neuronal membrane receptor rather than genomic action of the steroid.
内源性分泌或注射的皮质酮（CORT）通过作用于特定的神经元膜受体，迅速抑制雄性糙皮蝾螈（Taricha granulosa）的求偶抱握行为。先前使用固定蝾螈的研究表明，给予CORT会迅速降低网状脊髓神经元的兴奋性，并减弱延髓神经元对引发抱握的感觉刺激的反应性。本研究使用自由活动的蝾螈来检查抱握反应，并同时记录67个经逆向鉴定的网状脊髓神经元和其他延髓网状神经元在注射CORT前后的感觉运动特性。在注射CORT之前，网状脊髓神经元的放电与泄殖腔压力引发的抱握的开始和结束密切相关。网状脊髓神经元还表现出与非抱握运动事件（尤其是运动）相关的放电相关性。在抱握过程中神经元活动通常会减少，而在运动过程中会增加。未被逆向侵入的延髓神经元（未鉴定的神经元）通常表现出与网状脊髓神经元相似的感觉运动特性。腹腔注射CORT（而非溶剂）会降低后肢对泄殖腔压力做出抱握反应的概率和质量，尤其是在注射后的5 - 25分钟内。同时，网状脊髓神经元和未鉴定神经元对泄殖腔压力的反应以及与抱握相关活动的发生都会减弱或消除。CORT的作用具有相对选择性，与非抱握运动事件相关的活动相比，对与抱握相关的神经元活动的改变更强。CORT作用的特性表明，该激素通过抑制引发抱握的传入活动的处理以及破坏通常由网状脊髓神经元介导的抱握的延髓控制来损害抱握行为。这些CORT作用的快速起效意味着是神经元膜受体而非类固醇的基因组作用。
