RESUMEN
RATIONALE: Glutamate antagonists microinjected into the dorsolateral PAG (DLPAG) show an anxiolytic-like profile in the elevated plus maze. Other columns of the PAG are also involved in defensive reactions. Few studies, however, have investigated the effects of pharmacological manipulation of the ventrolateral PAG (VLPAG) on procedures that predict anxiolytic activity. OBJECTIVES: To investigate the effects of the NMDA receptor (NMDAr) antagonist 2-amino-7-phosphonoheptanoic acid (AP7) microinjected into the DL or VLPAG in two procedures that predict anxiolytic activity using distinct aversive contingencies, the elevated plus maze and the Vogel punished licking test. METHODS: Male Wistar rats (7-14/group) with cannulas aimed at the DLPAG or VLPAG received AP7 (2 nmol/0.5 microl) or saline and 10 min later were submitted to the behavioural tests. In the punished licking experiment, water deprived (48 h) animals were allowed to drink for 3 min, receiving a 0.5 mA shock every 20 licks. The elevated plus maze test was performed as described elsewhere. Using this test, a dose response-curve for AP7 (0.2-20 nmol) injected in a smaller volume (0.25 microl) into the VLPAG was also performed. RESULTS: AP7 increased exploration of open arms of the EPM when microinjected into either the DLPAG or VLPAG ( P<0.05, ANOVA). The drug also increased the number of punished licks when administered into those columns (ANOVA, P<0.05). CONCLUSIONS: The results suggest that antagonism of endogenous excitatory amino acid neurotransmission in the DLPAG or VLPAG is able to reverse behavioral suppression induced by distinct aversive contingencies.
Asunto(s)
2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacología , Ansiolíticos , Antagonistas de Aminoácidos Excitadores/farmacología , Sustancia Gris Periacueductal/fisiología , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , 2-Amino-5-fosfonovalerato/administración & dosificación , Animales , Ansiedad/psicología , Conducta Consumatoria/efectos de los fármacos , Inyecciones , Masculino , Dimensión del Dolor/efectos de los fármacos , Castigo , Ratas , Ratas Wistar , Tiempo de Reacción/efectos de los fármacosRESUMEN
The behavioral effects of trans-(+/-)-1-amino-1, 3-cyclopentanedicarboxylic acid (t-ACPD), a metabotropic glutamate receptor (mGluR) agonist, or 0.9% (w/v) saline, injected into the dorsal periaqueductal gray (DPAG), was investigated. Male Wistar rats showed defense reactions characterized by jumps toward the top edges of the cages (saline = 0 vs t-ACPD = 6.0, medians P<0.05) and gallops (saline = 0 vs t-ACPD = 10.0, medians P<0.05) during the 60-s period after the beginning of the injection. In another experiment animals were placed inside an open arena for 5 min immediately after injection. Their behavior was recorded by a video camera and a computer program analyzed the videotapes. Eleven of fifteen rats injected with t-ACPD showed a short-lasting (about 1 min) flight reaction. No saline-treated animal showed this reaction (P<0.0005, chi-square test). The drug induced an increase in turning behavior (P = 0.002, MANOVA) and a decrease in the number of rearings (P<0.001, MANOVA) and grooming episodes (P<0.001, MANOVA). These results suggest that mGluRs play a role in the control of defense reactions in the DPAG.
Asunto(s)
Cicloleucina/análogos & derivados , Mecanismos de Defensa , Fármacos Neuroprotectores/farmacología , Sustancia Gris Periacueductal , Receptores de Glutamato Metabotrópico/agonistas , Animales , Cicloleucina/farmacología , Reacción de Fuga/efectos de los fármacos , Masculino , Microinyecciones , Ratas , Ratas WistarRESUMEN
The behavioral effects of trans-(+ or -)-1-amino-1,3-cyclopentanedicarboxylic acid (t-ACPD), a metabotropic glutamate receptor (mGluR) agonist, or 0.9 per cent (w/v) saline, injected into the dorsal periaqueductal gray (DPAG), was investigated. Male Wistar rats showed defense reactions characterized by jumps toward the top edges of the cages (saline = 0 vs t-ACPD = 6.0, medians P<0.05) and gallops (saline = 0 vs t-ACPD = 10.0, medians P<0.05) during the 60-s period after the beginning of the injection. In another experiment animals were placed inside an open arena for 5 min immediately after injection. Their behavior was recorded by a video camera and a computer program analyzed the videotapes. Eleven of fifteen rats injected with t-ACPD showed a short-lasting (about 1 min) flight reaction. No saline-treated animal showed this reaction (P<0.0005, chi-square test). The drug induced an increase in turning behavior (P = 0.002, MANOVA) and a decrease in the number of rearings (P<0.001, MANOVA) and grooming episodes (P<0.001, MANOVA). These results suggest that mGluRs play a role in the control of defense reactions in the DPAG.