Right now this old rat is feeling a bit rusty and put-upon.

'I wonder where that old rat went just now,' he thought.

The first he had killed, unaware that it was an old and feeble rat.

For the older rats, a more prolonged signal may be required.

The older rats cannot respond that quickly and fail to complete the healing process.

The old rat was at a loss to know how to deal with this.

Today I feel like one old rat who wans to get off the exercise wheel.

New ideas needed a running jump to get into the old rat's head.

That has been observed in an experiment with young and old rats.

The place we went to that night had big old rats.