Adjusted to make it work for non-US langauges:
tell application "System Events"
set toggled to false
option key down
delay 0.1
try
click menu bar item "Notification Center" of menu bar 2 of application process "SystemUIServer"
set toggled to true
end try
if not toggled then
try
click menu bar item 1 of menu bar 2 of application process "SystemUIServer"
end try
end if
option key up
end tell