carried out this study in the whole brain synaptosomes.
However, there are various types of neurons in the brain, e.g.,
excitatory and inhibitory, hence it is possible that the responses
of some neurons may differ and also the effects would depend
on the duration of deprivation. This view may be supported by
the ﬁnding in slice preparation that although the dentate gyrus
granule neurons were not affected, the hippocampal CA1
neurons showed reduced ﬁring after REMSD (McDermott
et al., 2003). In related in vivo study it has been shown that the
ﬁring of REM-OFF neurons decreased, while that of REM-ON
neurons increased after REMSD (Mallick et al., 1989), while,
other neurons responded to lower intensity of auditory
stimulation (Mallick et al., 1991). Therefore, it is worth
studying the threshold and excitability of neurons in different
brain areas and speciﬁcally on neurochemically identiﬁed
neurons. Though this method has been used widely for
synaptosomal potential studies, it has a few limitations. The
dye might accumulate in different organelles or it might
remain bound to the synaptosomal membrane, thereby affecting
the ﬁnal ﬂuorescence intensity. However, since we have studied
relative changes in intensity, these are likely to be comparable
in the control samples, unless there is any speciﬁc reason to
believe that REMSD alters the synaptosomal membrane
property affecting its interactions with DiSC
In conclusion, we had proposed that REMSD alters brain
excitability but direct evidence was lacking. Although it was
known that REMSD increases NA that stimulates Na–K–
ATPase activity, we did not know how the enzyme gets
activated. It was also known that intracellular positivity
stimulates the enzyme. In this study, we observed that
indeed the intracellular positivity is increased after REMSD
Thus, the results of this study conﬁrm and provide
direct evidence in support of our hypothesis that REMSD
increases brain excitability and that is mediated by at
increased level of NA.
Research was supported by funding from Indian Council of
Medical Research and University Grants Commission, India.
GD received research fellowship from Council of Scientiﬁc and
Industrial Research, India.
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