Use keyboard command to toggle the Do Not Disturb option in OS X Notification Center
Turn the Do No Disturb option on or off with a keyboard command on your Mac
Here's how you can use a keyboard command to toggle the Do Not Disturb feature on or off in Notification Center in OS X.
1. Hold down the Option/Alt key.
2. Click the Notification Center on the far right of the menu bar.
3. Notification Center will be set to Do Not Disturb.
4. Repeat to disable Do Not Disturb.
For more, see the original article at the link below.