Stimulation of hippocampal 5-HT1A receptors causes amnesia and anxiolytic-like but not antidepressant-like effects in the rat.
Administration of 2 and 5 but not 0.4 microgram/microliter 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) into the CA1 region of the dorsal hippocampus 10 min before the acquisition trial in a passive avoidance task significantly reduced retention latencies 24 h later. The effect of 5 micrograms 8-OH-DPAT on retention latencies was completely antagonized by 1 microgram/microliter spiroxatrine, a 5-HT1A receptor antagonist, infused into the dorsal hippocampus 5 min before 8-OH-DPAT. Administered 5 min after the acquisition trial, 5 micrograms/microliters 8-OH-DPAT had no effect on retention latencies 24 h later. Administration of 5 micrograms/microliters 8-OH-DPAT into the dorsal hippocampus did not significantly change the thresholds for responses to the same electrical stimuli used in the passive avoidance task and had no antidepressant-like effect in the forced swimming test. The dose of 5 micrograms/microliters 8-OH-DPAT administered into the dorsal hippocampus caused anxiolytic-like effects assessed by stress-induced deficit in open field locomotor activity. The results suggest that stimulation of 5-HT1A receptors in the dorsal hippocampus impairs rats' performance in a passive avoidance task by interfering with memory processes or by attenuating the emotional impact of the shock through an anxiolytic action.
Carli
M
M
Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
Tatarczynska
E
E
Cervo
L
L
Samanin
R
R
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology*; D000647:Amnesia / Q000139:chemically induced*; D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D000928:Antidepressive Agents / Q000494:pharmacology*; D001362:Avoidance Learning / Q000187:drug effects; D004644:Emotions / Q000187:drug effects; D006624:Hippocampus / Q000033:anatomy & histology / Q000187:drug effects*; D007267:Injections; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009619:Nociceptors / Q000187:drug effects; D017288:Pain Threshold / Q000187:drug effects; D051381:Rats; D011985:Receptors, Serotonin / Q000187:drug effects*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013550:Swimming
D014151:Anti-Anxiety Agents; D000928:Antidepressive Agents; D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin