dc.description.abstract | Acetylcholine is an important neurotransmitter in the mammalian brain. This
transmitter binds to muscarinic acetylcholine receptors (mAChR) to regulate activity of a
variety of intracellular signaling molecules. Fyn and Src are two members of the Src family
kinase (SFK). They are highly expressed in many brain regions, including the striatum, an
area in the forebrain critical for cognitive, reward, mood, and movement. Since the striatum
is also among brain regions showing a high level of mAChR expression, it is intriguing to
investigate whether mAChRs regulate Fyn and Src. In this study, this topic was investigated
by testing the effect of pharmacological blockade of mAChRs on phosphorylation of Fyn and
Src at a specific tyrosine site, tyrosine 416 (Y416), a phosphorylation event leading to
activation of Fyn and Src. A widely used mAChR antagonist scopolamine was used to block
mAChRs and changes in phosphorylation of SFK Y416 were examined in the two
subdivisions of the striatum, i.e., the caudate putamen (CPu) and nucleus accumbens (NAc),
using Western blot with a phospho- and site-specific anti-Y416 antibody. We found that a
single intraperitoneal injection of scopolamine at an effective dose (5 mg/kg) induced a
significant increase in Y416 phosphorylation in the CPu. A similar increase in Y416
phosphorylation was also seen in the NAc following scopolamine administration. The
scopolamine-stimulated Y416 phosphorylation was time-dependent. No significant change
occurred to the amount of total Fyn and Src proteins in the two regions. These results
indicate that mAChRs exert an inhibitory effect on basal phosphorylation of Fyn and Src in
striatal neurons under normal conditions. | eng |