| Abstract No.: | C-D3148 |
| Country: | Brazil |
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| Title: | GLYCINE MICROINJECTION INTO DPAG INDUCES HYPER AND HYPONOCICEPTION DEPENDING ON DOSE, SEX AND LOCAL OF NOCICEPTIVE STIMULUS. |
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| Authors/Affiliations: | 1 Maria Alcina Martins*; 1 Lúcia de Castro Bastos; 1 Carlos Rogério Tonussi; 1 Antônio de Pádua Carobrez;
1 Federal University of Santa Catarina, Florianópolis, Brazil
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| Content: | Objectives: Periaqueductal gray matter (PAG) stimulation produces either inhibition or facilitation of nociceptive transmission. However, it is still not clear how these mechanisms can be used in freely behaving animals. The aim of this study was to verify the effect of different levels of PAG activation on persistent nociception in superficial and deep tissue, in male and female rats. Materials and Methods: Glycine (GLY; 10, 20 and 80 nmols / 0.3 µl) microinjection into dorsal PAG (DPAG) of Wistar male and female rats was made 5 min before formalin (2% / 50 µl) injection into knee-joint and hindpaw. Nociception was evaluated during 1 hour by the paw elevation time (PET, s) and the number of paw shaking (PS) after formalin injection, respectively. Results: In female rats, GLY (10 and 80 nmol) microinjection into DPAG evoked hypernociception in the knee-joint test (PETcontrol: 40.76 ± 4.9 s; PETGLY80: 52.00 ± 4.62 s at 25 min) and in paw test (PScontrol: 49.63 ± 8.96 s and PSGLY10: 81.56 ± 7.84 s, at 35 min). In males, GLY (10 and 20 nmols) produced hypernociceptive effect (PETcontrol: 28.96 ± 3.99 s; PET GLY10: 37.08 ± 6.35 s and PET GLY20: 33.81 ± 2.63 s, at 20 min), while 80 nmols produced hyponociceptive effect (PETcontrol: 47.27± 3.60 s; PET GLY80: 29.05 ± 4.64 s, at 20 min), in the knee-joint test. In the paw test, only a hypernociceptive effect with the higher dose was observed (PScontrol: 53.90 ± 6.57 s and PS GLY80: 93.50 ± 8.94 s, at 35min). Both effects, hyper and hyponociception were blocked by the co-administration of GLY with (±)-3-amino-1-hydroxy-2-pyrrolidone (10 nmols / 0.3 µl) or 7-clorokynurenic acid (10 nmols / 0.3 µl), glycine site-specific / NMDA (N-methyl-D-aspartate) antagonists. Conclusion: It was shown here that glycine microinjection into DPAG is able to produce either facilitation or inhibition of persistent nociception, via glycine site-specific / NMDA. The glycine effects on PAG seem to be determined by sex and nociceptive model.
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