A. Alonso et al., DIFFERENTIAL OSCILLATORY PROPERTIES OF CHOLINERGIC AND NONCHOLINERGICNUCLEUS BASALIS NEURONS IN GUINEA-PIG BRAIN SLICE, European journal of neuroscience, 8(1), 1996, pp. 169-182
Evidence has suggested that the nucleus basalis magnocellularis has th
e potential to influence the functional state of the cerebral cortex t
hrough topographically organized, widespread projections of the cholin
ergic cells in that nucleus. It has also been shown that, in addition
to the cholinergic neurons, other non-cholinergic magnocellular basal
forebrain neurons, some of which have been identified as gamma-aminobu
tyric acid-ergic, project into the cerebral cortex and thus may also p
articipate in the modulation of its activity. We have performed a comp
arative study of the intrinsic rhythmic properties of immunohistochemi
cally and morphologically characterized choline acetyltransferase (ChA
T)-positive and ChAT-negative cells of the nucleus basalis by means of
intracellular recordings in guinea pig brain slices. Our results demo
nstrate that relatively large, multipolar cholinergic and non-choliner
gic neurons each display differential voltage-dependent properties tha
t allow them to discharge rhythmically in spike bursts and spike clust
ers, respectively, at low frequencies (<10 Hz). Cholinergic cells disp
lay bursts of 2-4 action potentials (at similar to 200 Hz) riding on l
ow-threshold spikes recurring at a low frequency (<5 Hz) when depolari
zed from a membrane potential more negative than -55 mV and display lo
w-frequency (<10-15 Hz) tonic firing when depolarized from a more posi
tive level. In contrast, non-cholinergic cells fire in a unique mode,
displaying non-adapting clusters of spikes interspersed with rhythmic
subthreshold membrane-potential oscillations when depolarized from lev
els less negative than -55 mV. The spike clusters repeat rhythmically
at relatively low frequencies (2-10 Hz). The intracluster spiking freq
uency is relatively high and coincides approximately with that of the
intervening membrane-potential oscillations (similar to 20-70 Hz). The
duster frequency of the non-cholinergic cells corresponds, in the sam
e manner as the burst frequency of the cholinergic cells, to a delta (
1-4 Hz) or theta (4-10 Hz) range of activity, whereas the intra-cluste
r and tonic spike frequencies of the non-cholinergic cells correspond
to high beta to gamma ranges of electroencephalographic activity (19-3
0 Hz and 30-60 Hz, respectively). We propose that the different modes
of oscillatory firing by the cholinergic and non-cholinergic basal for
ebrain cell populations could collectively contribute to the rhythmic
modulation of slow and fast rhythms within the cerebral cortex.