Journal of Neuroscience, Vol 6, 2535-2542, Copyright © 1986 by Society for Neuroscience
Nucleus basalis involvement in conditioned neuronal responses in the rat frontal cortex
GC Rigdon and JH Pirch
Rat frontal cortex neurons exhibit alterations in firing in response to a 2
sec tone cue followed by rewarding medial forebrain bundle (MFB)
stimulation. Nucleus basalis neurons supply up to 75% of the cortical
cholinergic innervation. The nucleus basalis and ACh have been implicated
as playing a role in cognitive function. Three experiments were designed to
test the hypothesis that the nucleus basalis cholinergic system is involved
in the generation of conditioned neuronal responses in the rat frontal
cortex. Local microinjection of the cholinergic antagonist, atropine, into
the frontal cortex suppressed the conditioned responses of 22 of 25
cortical single units. Unilateral kainic acid lesioning of the nucleus
basalis resulted in a significant decrease in the proportion of units
exhibiting conditioned responses in the cortex ipsilateral to the lesion
(25%) compared to the proportion of responding units from the cortex of
untreated animals (70%). When the firing rates of units encountered in the
region of the nucleus basalis were monitored during presentation of the
cue-MFB paradigm, 28 of 38 unit recordings exhibited significant increases
or decreases in firing rate. Therefore, the results of the experiments
indicate that the nucleus basalis cholinergic neurons are involved in the
generation of conditioned neuronal responses in the rat frontal cortex.
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