The effects of 8-hydroxy-2-(di-n-propylamino)tetralin and other serotonergic agonists on performance in a radial maze: a possible role for 5-HT1A receptors in memory

A group of ten rats was trained to obtain food pellets in an 8-arm radial maze. The effects of pretreatment with (+)-Lysergic acid diethylamide (+)-tartrate (LSD), m-trifluoromethylphenylpiperazine (TFMPP), 5-methoxy-N,N-dimethyltryptamine oxalate (5-MeO-DMT), racemic 8-hydroxy-2-(di-n-propylamino)tetralin HBr (8-OH-DPAT), and 5-methoxy-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-indole succinate (RU 24969) were then evaluated. All drugs were administered IP 15 min before testing. With the exception of an increased rate of responding at a dose of 0.1 mg/kg of 8-OH-DPAT, all drugs produced a dose-related decline in response rate. In addition, LSD, RU 24969, and 8-OH-DPAT caused a statistically significant decrease in efficiency of responding. Of the three, 8-OH-DPAT was clearly the most active. Doses of 0.3, 1.0, and 3.0 mg/kg resulted in efficiencies of 61%, 53%, and 44%, respectively. The present results taken in light of 8-OH-DPAT's preferential binding to 5-HT1A receptors, the high density of these receptors in hippocampus, and the observation that the number of 5-HT1A receptors is decreased in Alzheimer's disease, suggest a possible role for this serotonergic receptor subtype in memory.