The Journal of Neuroscience, September 1, 1999, 19(17):7661-7669
Redundant Basal Forebrain Modulation in Taste Aversion Memory
Formation
Humberto
Gutiérrez,
Ranier
Gutiérrez,
Luis
Ramírez-Trejo,
Ricardo
Silva-Gandarias,
Christopher E.
Ormsby,
María Isabel
Miranda, and
Federico
Bermúdez-Rattoni
Instituto de Fisiología Celular Universidad Nacional
Autónoma de México, Apartado Postal 70-253, 04510 México, D.F., México
Mnemonic deficits resulting from excitotoxic lesion of the basal
forebrain have been classically attributed to the resulting depletion
of cortical acetylcholine activity. It has been demonstrated that in
spite of the strong cholinergic depletion after injections into the
basal forebrain of the immunotoxin 192IgG-saporin, no detectable
deficit can be found in the acquisition of several learning tasks,
including conditioned taste aversion. Conversely, NMDA-induced
lesions of the basal forebrain strongly impair taste aversion learning.
In this study we show that 192IgG-saporin produces an efficient and
selective cholinergic deafferentation of the rat neocortex but not the
amygdala. Furthermore, a stronger relationship between severity of
memory impairment after NMDA lesions and basoamygdaloid cholinergic
deafferentation was found. Therefore, in a second experiment, we show
that combining NMDA-induced lesions into the basolateral amygdala with
192IgG-saporin injections into the basal forebrain results in a strong
disruption of taste aversion learning, whereas none of these treatments
were by themselves capable of producing any detectable impairment in
this learning task. The double lesion effect was only paralleled by
simple NMDA lesions into the basal forebrain, suggesting that the
learning deficits associated to excitotoxic lesions of the basal
forebrain are the result of the simultaneous destruction of the
corticopetal and basoamygdaloid interaction. A model is proposed,
according to which the modulation of learning processes exerted by the
basal forebrain can be redundantly performed by both the basocortical and basoamygdaloid pathway.
Key words:
conditioned taste aversion; learning; cholinergic basal
forebrain; ChAT; insular cortex; amygdala
Copyright © 1999 Society for Neuroscience 0270-6474/99/19177661-09$05.00/0
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