K. Arakawa et al., DIFFERENT EFFECTS OF CHOLINERGIC AGENTS ON RESPONSES RECORDED FROM THE CAT VISUAL-CORTEX AND LATERAL GENICULATE-NUCLEUS DORSALIS, Electroencephalography and clinical neurophysiology. Evoked potentials, 104(4), 1997, pp. 375-380
We investigated the effect of cholinergic agents on the cat visual evo
ked potentials (VEPs) recorded from the primary visual cortex (V1) and
lateral geniculate nucleus dorsalis (LGNd) to determine on which leve
l of the visual pathway the cholinergic system acts. VEPs to the alter
nation of 0.1 cycles per degree sinusoidal gratings at 1 and 4 Hz were
recorded from N2O-anesthetized cats directly from the surface of V1 a
nd LGNd The depth of recording in LGNd was determined by the site wher
e the maximal response was obtained by 1 Hz stimulation, VEPs to 4 Hz
stimulation, which showed sinusoidal waveforms and were analyzed by fa
st Fourier transforms, were used as indicators for modulation by choli
nergic agents, Physostigmine, an acetylcholinesterase inhibitor, 0.7 m
g/kg i.v., suppressed the amplitude of the responses more at V1 (suppr
ession ratio: mean +/- SD, 85.4 +/- 9.3%) than at LGNd (32.4 +/- 30.7%
) (P < 0.05). Conversely, scopolamine, a muscarinic receptor blocker,
0.7 mg/kg i.v., increased the amplitude of the responses more at V1 (e
nhancement ratio: mean +/- SD, 60.3 +/- 22.3%) than at LGNd (-22.2 +/-
22.5%) (P < 0.05). These results indicate that the V1 changes reflect
a direct cortical cholinergic effect, probably by modulating the chol
inergic projection from the nucleus basalis of Meynert to V1. (C) 1997
Elsevier Science Ireland Ltd.