Anxiogenic effects in the rat elevated plus-maze of 5-HT(2C) agonists into ventral but not dorsal hippocampus.
The effect of the non-selective 5-HT2C receptor agonist trifluoromethyl-phenylpiperazine (TFMPP, 0.75, 1.5 and 3.0 microg) and the preferential 5-HT2C agonist 6-chloro-2(1-piperazinyl)pyrazine (MK-212, 0.1, 0.3 and 1.0 microg) microinjected into the ventral or dorsal hippocampus was investigated in anxiety measures of rats exposed to the elevated plus-maze test. Ventral hippocampal (VH) microinjections of the 0.75 or 1.5 microg doses of TFMPP reduced open-arm exploration without affecting the number of closed-arm entries, indicating a selective anxiogenic profile. The highest dose (3.0 microg) reduced open- and closed-arm entries, suggesting interference in locomotor activity. The 0.1 microg dose of MK-212 also caused a selective anxiogenic effect when microinjected into the ventral hippocampus, without disturbing locomotor activity. Microinjections of the two higher doses of MK-212 (0.3 or 1.0 microg) into the ventral hippocampus led to a decrease of exploration in both arms of the maze. In contrast to the anxiogenic effect observed in the VH, neither TFMPP nor MK-212 significantly changed anxiety measures when microinjected into the dorsal hippocampus. These results suggest that activation of 5-HT2C postsynaptic receptors located in the ventral, but not in the dorsal, hippocampus play an important role in anxiety triggered by the elevated plus-maze test.
Alves
S H
SH
Departamento de Processos Psicológicos Básicos, Instituto de Psicologia, Universidade de Brasília, Brasília, Brazil.
Pinheiro
G
G
Motta
V
V
Landeira-Fernandez
J
J
Cruz
A P M
AP
D000818:Animals; D001143:Arousal / Q000187:drug effects*; D001931:Brain Mapping; D004305:Dose-Response Relationship, Drug; D005239:Fear / Q000187:drug effects*; D006624:Hippocampus / Q000187:drug effects*; D008297:Male; D018782:Maze Learning / Q000187:drug effects*; D008845:Microinjections; D010879:Piperazines / Q000494:pharmacology*; D011719:Pyrazines / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D058826:Serotonin 5-HT2 Receptor Agonists; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*
D010879:Piperazines; D011719:Pyrazines; D058826:Serotonin 5-HT2 Receptor Agonists; D017366:Serotonin Receptor Agonists; C018406:1-(3-trifluoromethylphenyl)piperazine; C014896:6-chloro-2-(1-piperazinyl)pyrazine