Avaliação da injeção na substância cinzenta periaquedutal de agonista serotonérgico em camundongos submetidos à constrição crônica do nervo ciático : efeitos nos testes de nocicepção e ansiedade
Reis, Luciana Maria dos
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Studies have shown that situations of anxiety/fear can inhibit nociception and serotonin (5-HT) has antinociceptive effect in the brain structures such as the periaqueductal gray matter (PAG). This work aimed to evaluate the effect of anxiety/fear in nociception-induced model of sciatic nerve constriction (CNC), and infused intra-ventrolateral PAG (PAGvl) of 8-OH-DPAT (5- HT1A agonist), nociception and anxiety/fear datas. Male mice, Swiss albino (n = 7-15/group) were exposed to the real rat (RR) and toy rat (TR), for registration of nociception (total scratching) and anxiety/fear [total entries (TE), percentage of protected entries (% PE) and time spent (% PT) in the apparatus and behaviors of self-cleaning, rearing and total immobility (s)], as well as tests of mechanical and termic hyperalgesia. Experiment 1, performed without drug administration, showed that animals with CNC had an increase in total scratching compared to SHAM group being, this index decreased by exposure to RR. It also showed an increase in % PE and % PT in animals exposed to RR. In Experiment 2, the 8-OH-DPAT (5.6 nmol/0.1 μl) intra- PAG of mice with CNC, decreased levels of anxiety (TE, % PE, and % PT) only in animals exposed to RR, without decreasing the indices in SHAM animals. The 10 nmol/0.1 μl dose takes effect only in increased % PT and immobility time in animals exposed to TR. None doses of 8- OH-DPAT was able to modify the nociceptive response (scratching and frequency of mechanical and thermal hyperalgesia tests). Together, we conclude that exposure of mice to the predator (rat) produced increased anxiety/fear in both SHAM or CNC mice, and reduction measures of nociception only in CNC animals. The 5-HT1A receptor agonist in 5.6 nmol dose, intra-PAGvl, produced anxiolytic effects in CNC mice without altering the levels of pain, while the 10 nmol dose effects produced suggestive nociception increased. Thus, these results support the involvement of the 5-HT1A receptors in modulating responses PAGvl anxiety/fear and nociception evaluated in rodents.