Involvement of dorsolateral periaqueductal gray N-methyl-D-aspartic acid glutamate receptors in the regulation of risk assessment and inhibitory avoidance behaviors in the rat elevated T-maze.
The involvement of the dorsolateral periaqueductal gray in the regulation of fear-related behaviors such as escape and freezing is well established. It is still a matter of investigation, however, whether this midbrain area may have a relevant role in the modulation of more subtle defensive responses associated with anxiety such as risk assessment and inhibitory avoidance. By stimulating N-methyl-D-aspartic acid glutamate receptors located in the dorsolateral periaqueductal gray with its prototypical agonist N-methyl-D-aspartic acid (50 pmol), we report here an increase in both risk assessment and inhibitory avoidance behaviors of male Wistar rats tested in the elevated T-maze. These results are indicative of an anxiogenic-like effect. The selective N-methyl-D-aspartic acid receptor antagonist DL-2-amino-7-phosphonoheptanoic acid (2.0 and 4.0 nmol) had the opposite effect on both defensive tasks. Pretreatment with an ineffective dose of DL-2-amino-7-phosphonoheptanoic acid (1.0 nmol) prevented the N-methyl-D-aspartic acid anxiogenic-like effect. At the dose range of DL-2-amino-7-phosphonoheptanoic acid and/or N-methyl-D-aspartic acid tested, neither the escape response from one of the elevated T-maze open arms nor the general exploratory activity as assessed in the open-field test was affected. The present results suggest that the dorsolateral periaqueductal gray column is also involved in the regulation of defensive behaviors related to anxiety, and N-methyl-D-aspartic acid glutamate receptors are recruited for this action.
Bertoglio
Leandro José
LJ
Department of Pharmacology, School of Medicine, University of São Paulo, São Paulo, Brazil. lejobe@usp.br
Zangrossi
Hélio
H
D015763:2-Amino-5-phosphonovalerate / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology; D001007:Anxiety / Q000188:drug therapy* / Q000523:psychology*; D005013:Ethosuximide / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000008:administration & dosage / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D005106:Exploratory Behavior / Q000187:drug effects; D005239:Fear / Q000187:drug effects* / Q000523:psychology*; D006624:Hippocampus / Q000502:physiology; D008297:Male; D008845:Microinjections; D016202:N-Methylaspartate / Q000008:administration & dosage / Q000494:pharmacology; D010487:Periaqueductal Gray / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects*; D012309:Risk-Taking
D000927:Anticonvulsants; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D005013:Ethosuximide; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; C031231:2-amino-7-phosphonoheptanoic acid