Changes in exploratory activity following stimulation of hippocampal 5-HT1A and 5-HT1B receptors in the rat.
The object exploration task allows the measure of changes in locomotor and exploratory activities, habituation, and reaction to a spatial change and to novelty. The effects of intrahippocampal (dorsal CA1 field) microinjections of serotonin 1 receptor (5-HT1) agonists on these behavioral components were evaluated in the rat. 8-Hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT, 5 micrograms/microliters) was used as a 5-HT1A agonist, 3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo[3,2-b]pyrid-5-one (CP 93,129,16 micrograms/microliters) as a 5-HT1B agonist, and scopolamine (10 micrograms/microliters) as a muscarinic cholinergic antagonist. Scopolamine induced a long-lasting increase in locomotor activity and a lack of reaction to spatial change; both these results are in agreement with the known crucial influence of the septo-hippocampal cholinergic system in hippocampal functioning. Stimulation of 5-HT1A and 5-HT1B receptors induced a decrease in object exploration and habituation without affecting the retrieval of spatial information. But stimulation of hippocampal 5-HT1B receptors induced a selective change in the animal's emotional state, i.e., an initial decrease in locomotor activity and a neophobic reaction in response to a new object; such effects did not occur following stimulation of 5HT1A receptors. These results have to be considered in the light of the anxiogenic property of 5-HT1B agonists. On the whole, they support the hypothesis of the involvement of the serotonergic system, via 5HT1A and 5-HT1B receptors, in the modulation of hippocampal functions.
Buhot
M C
MC
Centre National de la Recherche Scientifique, CNRS URA 339, Université de Bordeaux I, France.
Naïli
S
S
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D005106:Exploratory Behavior / Q000187:drug effects / Q000502:physiology*; D006185:Habituation, Psychophysiologic; D006624:Hippocampus / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000502:physiology*; D012601:Scopolamine / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013028:Space Perception; D013268:Stimulation, Chemical
D011725:Pyridines; D011758:Pyrroles; D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; C065046:3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo(3,2-b)pyrid-5-one; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D012601:Scopolamine