Department of Physiology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, 14049-900 Ribeirão Preto, SP, Brazil.
Behav Brain Res. 2010 Mar 17;208(1):237-42. doi: 10.1016/j.bbr.2009.11.047. Epub 2009 Dec 4.
Tonic immobility (TI) is an innate defensive behaviour elicited by physical restriction and postural inversion, and is characterised by a profound and temporary state of akinesis. Our previous studies demonstrated that glutamatergic stimulation of the dorsomedial/dorsolateral portion of periaqueductal gray matter (dPAG) decreases the duration of TI in guinea pigs (Cavia porcellus). Furthermore, evidence suggests that the anterior cingulate cortex (ACC) constitutes an important source of glutamate for the dPAG. Hence, in the current study, we investigated the effects of microinjection of the excitatory amino acid (EAA) agonist DL-homocysteic acid (DLH) and the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 into the ACC on the duration of TI in guinea pigs. We also assessed the effect of the NMDA receptor antagonist (MK-801) into the dorsal periaqueductal gray matter (dPAG) prior to DLH microinjection into the ACC on the TI duration in the guinea pig. Our results demonstrated that DLH microinjections into the ACC decreased the duration of TI. This effect was blocked by previous MK-801 microinjections into the ACC or into the dPAG. The MK-801 microinjections alone did not influence TI duration. These results provide the new insight that EAAs in the ACC can decrease the duration of TI. The mechanism seems to be dependent on the NMDA receptors present in the ACC and in the dPAG.
强直不动（TI）是一种由身体限制和姿势反转引起的先天防御行为，其特征是深度暂时的无运动状态。我们之前的研究表明，缰核背内侧/背外侧部的谷氨酸刺激可缩短豚鼠（Cavia porcellus）的 TI 持续时间。此外，有证据表明，前扣带回皮层（ACC）是缰核的谷氨酸的重要来源。因此，在本研究中，我们研究了将兴奋性氨基酸（EAA）激动剂 DL-高半胱氨酸（DLH）和 N-甲基-D-天冬氨酸（NMDA）受体拮抗剂 MK-801 微注射到 ACC 对豚鼠 TI 持续时间的影响。我们还评估了 NMDA 受体拮抗剂（MK-801）在将 DLH 微注射到 ACC 之前注射到背侧缰核（dPAG）对豚鼠 TI 持续时间的影响。我们的结果表明，DLH 微注射到 ACC 会缩短 TI 持续时间。这一作用被之前将 MK-801 微注射到 ACC 或 dPAG 所阻断。单独注射 MK-801 并不影响 TI 持续时间。这些结果提供了新的见解，即 ACC 中的 EAAs 可以缩短 TI 的持续时间。该机制似乎依赖于存在于 ACC 和 dPAG 中的 NMDA 受体。
