Vieira-Rasteli Eveline Bis, de Paula Bruna Balbino, de Paiva Yara Bezerra, Coimbra Norberto Cysne, Leite-Panissi Christie Ramos Andrade
Department of Psychology, School of Philosophy, Science and Literature of Ribeirão Preto of the University of São Paulo, 14040-901 Ribeirão Preto, SP, Brazil.
Department of Pharmacology, Medical School of Ribeirão Preto of the University of São Paulo, 14049-900 Ribeirão Preto, SP, Brazil.
Physiol Behav. 2018 Oct 1;194:538-544. doi: 10.1016/j.physbeh.2018.07.003. Epub 2018 Jul 10.
Tonic immobility (TI) is an innate defensive response exhibited by prey when physical contact with a predator is prolonged and inescapable. This defensive response is able to activate analgesia mechanisms; this activation has adaptive value because, during an attack by a predator, the manifestation of recuperative behaviors can affect the appropriate behavioral defense strategy. Some studies have suggested that similar structures of the central nervous system can regulate the response of both TI and nociception. Thus, this study evaluated the effect of chemical lesion through the administration of ibotenic acid in restricted brain areas of the periaqueductal gray matter (PAG) in guinea pig on the TI response and nociception evaluated in the hot plate test before and after emission of TI. The data showed that an irreversible chemical lesion in the ventrolateral PAG reduced of the TI response as well as defensive antinociception. However, a lesion in the dorsal PAG blocked the defensive antinociception induced by TI but did not alter TI duration. In summary, one could hypothesize that the neural substrates responsible for defensive behavior and antinociception represent similar systems that are distinct in modulation. Thus, the ventrolateral PAG has been associated with the modulation of TI and the defensive antinociception induced by TI. In contrast, the integrity of the dorsal PAG should be necessary for defensive antinociception to occur but not to elicit TI behavior in guinea pigs.
强直静止（TI）是猎物在与捕食者的身体接触持续且无法逃避时表现出的一种先天性防御反应。这种防御反应能够激活镇痛机制；这种激活具有适应性价值，因为在捕食者攻击期间，恢复行为的表现可能会影响适当的行为防御策略。一些研究表明，中枢神经系统的类似结构可以调节TI和痛觉感受的反应。因此，本研究通过向豚鼠中脑导水管周围灰质（PAG）的特定脑区注射鹅膏蕈氨酸来评估化学损伤对TI反应和在TI发生前后通过热板试验评估的痛觉感受的影响。数据显示，腹外侧PAG的不可逆化学损伤降低了TI反应以及防御性抗伤害感受。然而，背侧PAG的损伤阻断了TI诱导的防御性抗伤害感受，但并未改变TI的持续时间。总之，可以推测负责防御行为和抗伤害感受的神经基质代表了在调节方面不同的类似系统。因此，腹外侧PAG与TI的调节以及TI诱导的防御性抗伤害感受有关。相比之下，背侧PAG的完整性对于豚鼠发生防御性抗伤害感受是必要的，但对于引发TI行为并非必要。
