nAChR. ANI alone evoked minimal responses compared to ACh but suppressed subsequent
responses to ACh (Fig 2). ANI produced no detectable responses in oocytes that were not
injected with RNA for nAChR subunits (not shown). When 10 μMof the α7-selective PAM
PNU-120596 [31] was added to the ANI, the α7-expressing cells showed responses that were
much larger than those evoked by ACh alone. PNU-120596 is known to destabilize desensitized
states of α7 nAChR and so typically evokes responses that are much more prolonged than
those stimulated by ACh or other α7 agonists [32]. When used in combination with ACh in
our system, PNU-120596-potentiated responses normally decay well back to baseline during
the normal washout procedure [32]. However, potentiated ANI responses were biphasic and
only partially decayed through the washout period. When 60 μMACh was applied 4 minutes
after the initial ANI application, there was a transient increase in current added to the still
decaying responses to the previous application of ANI plus 10 μM PNU-120596.
There are many potentially active molecules in the areca nut, including numerous alkaloids,
with the most abundant and active for producing responses in central and peripheral nervous
system tissues being arecoline, a muscarinic agonist with activity at M1, M2, and M3-typ