RESUMO
The glutamatergic system of the dorsal periaqueductal gray matter (DPAG) has been implicated in anxiety. This study shows that microinjections of glycine (GLY) or D-serine (D-SER), into the DPAG of rats, dose-dependently reduced the number of entries and the time spent on open arms of an elevated plus-maze (EPM), an established animal model for measuring anxiety-related behavior. This anxiogenic-like effect was greatest following DPAG application of either 80 nmol GLY or 160 and 320 nmol D-SER. Microinjections of these same amino acid doses outside the DPAG, or of L-serine (320 nmol) inside the DPAG, produced neither of these pro-anxiety effects. The current results suggest that, in vivo, the GLY modulatory site of N-methyl-D-aspartate receptors is not fully saturated, and further substantiate a role for the DPAG excitatory amino acid system in anxiety.
Assuntos
Ansiedade/induzido quimicamente , Glicina/farmacologia , Substância Cinzenta Periaquedutal/fisiologia , Serina/farmacologia , Animais , Ansiedade/psicologia , Relação Dose-Resposta a Droga , Glicina/administração & dosagem , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Microinjeções , Substância Cinzenta Periaquedutal/anatomia & histologia , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/metabolismo , Serina/administração & dosagem , EstereoisomerismoRESUMO
We have compared the performance of male and female Wistar rats at different ages (45, 60, 90, 120 and 150 days) in the elevated plus-maze test, a reliable animal model of anxiety. Up to 60 days of age, rats of both sexes exhibited a high number of entries and of time spent on open arms (50% or above). At 120 days of age or more, rats of both sexes characteristically exhibited a reduction in the number of entries and of the time spent on open arms (below 50%). Within the range of 60 and 120 days there are statistically significant sex differences. At 90 days of age male rats showed a marked switch in their performance in the apparatus, reaching levels of the latter stage, whereas in females it happened around 120 days. These results suggest an ontogenetic difference in rats that accounts for at least two distinct performances for rats placed in an elevated plus-maze. Gender effects were found in a certain range, suggesting caution on interpreting data obtained in rats within 60 and 120 days old. Also, the results obtained highlight the importance of carefully controlling animal age in studies using the elevated plus-maze.
Assuntos
Envelhecimento/fisiologia , Nível de Alerta/fisiologia , Aprendizagem por Discriminação/fisiologia , Comportamento Exploratório/fisiologia , Medo/fisiologia , Orientação/fisiologia , Animais , Feminino , Masculino , Atividade Motora/fisiologia , Psicofisiologia , Ratos , Fatores Sexuais , Meio SocialRESUMO
The effect of kynurenic acid (20 to 160 nmol) microinjected into the dorsal periaqueductal gray matter was measured in rats placed in an elevated plus-maze. Microinjection of 160 nmol of kynurenic acid increased the percentages of open arm entries and of time spent in the open arms. Both of these measures may be considered indexes of anxiolysis. Although kynurenic acid also increased the total number of entries, analysis of covariance shows that the increase in open arm entries is independent of the effect on closed arm entries. Thus, the anxiolytic effect of kynurenic acid detected in the elevated plus-maze strengthens the proposal that glutamatergic neurons of the dorsal periaqueductal gray matter play an important role in anxiety.
Assuntos
Ansiedade/tratamento farmacológico , Comportamento Exploratório/efeitos dos fármacos , Ácido Cinurênico/farmacologia , Substância Cinzenta Periaquedutal/fisiologia , Análise de Variância , Animais , Ácido Cinurênico/administração & dosagem , Masculino , Ratos , Ratos EndogâmicosRESUMO
The effect of kynurenic acid (20 to 19=60 nmol) microinkected into the dorsal periaqueductal gray matter was measured in rats placed in a elevated plus-maze. Microinjection of 160 nmol of kynurenic acid increased the percentages of open arm entries and of time spent in the open arms. Both of these measures may be considered indexes of anciolysis. Although kynurenic acid also invreased the total number of entries, analysis of covariance shows that the increase in open arm entries is independent of the effect on closed arm entries. Thus, the anxiolytic effect of kynurenic acid detected in the elevated plus-maze strengthens the proposal that glutamatergic neurons of the dorsal periaqueductal gray matter paly an important role in anxiety