Enhancement of passive avoidance learning through small doses of intra-amygdaloid physostigmine in the young rat. Its relation to the development of acetylcholinesterase

Authors

  • Vincent Dumery,

    1. Université Pierre et Marie Curie-C.N.R.S. UA 1199, Institut des Neurosciences, Département de Neurophysiologie Comparée, 9 quai Saint Bernard, F-75005 Paris, France
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  • Paul Derer,

    1. Université Pierre et Marie Curie-C.N.R.S. UA 1199, Institut des Neurosciences, Département de Cytologie, 9 quai Saint Bernard, F-75005 Paris, France
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  • Denise Blozovski

    Corresponding author
    1. Université Pierre et Marie Curie-C.N.R.S. UA 1199, Institut des Neurosciences, Département de Neurophysiologic Comparée, 9 quai Saint Bernard, F-75005 Paris, France
    • Université Pierre et Marie Curie-C.N.R.S. UA 1199, Institut des Neurosciences, Departement de Neurophysiologie Comparée, 9 quai Saint Bernard, F-75005 Paris, France
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Abstract

Passive avoidance learning was studied in young rats 7-20 days old, in control conditions and after bilateral injections of physostigmine into the lateral amygdaloid nucleus. Acquisition in controls was possible from postnatal Day 8 on, progressed markedly after Day 11, and nearly reached maturity by Day 20. Physostigmine differentially altered acquisition depending on the dose: facilitation with low doses, no effect with moderate doses, and impairment with high doses. Enhanced learning through small doses of physostigmine was observed at all ages from Day 8 on, and was greater with 0.2 μg than with 0.1 μg. Maturation of the cholinergic innervation of the amygdaloid region was also studied between Days 9-20 using acetylcholine-esterase histochemistry. The results suggest that passive avoidance learning is dependent on amygdaloid cholinergic mechanisms early in life. In addition, very immature cholonergic systems, which are known to be uninfluenced by anticholinesterases.

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