Selective lesions of the entorhinal cortex, the hippocampus, or the fimbria-fornix in rats: a comparison of effects on spontaneous and amphetamine-induced locomotion.
Using adult Long-Evans male rats, this experiment compared spontaneous (assessed 15 days and 4.5 months after surgery) and amphetamine-induced (assessed from 4.5 months after surgery onwards; 1 mg/kg, i.p., ten injections, 48 h apart) locomotor activity following N-methyl-D-aspartate lesions of the entorhinal cortex, electrolytic lesions of the fimbria-fornix, or ibotenate lesions of the hippocampus. Sham-operated rats were used as controls. Hippocampal and fimbria-fornix lesions, but not entorhinal-cortex lesions induced diurnal and nocturnal hyperactivity, which was attenuated over time, but only in rats with fimbria-fornix lesions. Amphetamine-induced hyperlocomotion was assessed in a familiar environment. Lesions of the entorhinal cortex potentiated the locomotor effects of amphetamine, but not lesions of the hippocampus or interruption of the axons in the fimbria-fornix pathway. Sensitization appeared to be decreased by fimbria-fornix lesions and to be prevented by hippocampal lesions. Rats with entorhinal-cortex lesions behaved as if they had already been sensitized by the lesion. These results clearly show that lesions of the fimbria-fornix, the hippocampus, and of the entorhinal cortex have different effects on spontaneous and amphetamine-induced hyperactivity, as they also have on learning and memory tasks.
Coutureau
E
E
Laboratoire de Neurosciences Comportementales et Cognitives, UMR 7521 ULP/CNRS, Strasbourg, France.
Galani
R
R
Jarrard
L E
LE
Cassel
J C
JC
D000661:Amphetamine / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D004572:Electrolysis; D018728:Entorhinal Cortex / Q000187:drug effects / Q000502:physiology*; D020712:Fornix, Brain / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology*; D016202:N-Methylaspartate / Q000633:toxicity; D051381:Rats; D020318:Rats, Long-Evans; D013238:Stereotaxic Techniques
D016202:N-Methylaspartate; D000661:Amphetamine