2000 Chevy S-10 Oil Pressure Guage

When I start the truck (and it's been cold in Indiana lately) the oil pressure guage shows a high reading, nearly at the highest level.

Once the engine warms up, the reading's more in the middle range. But when I accelerate, the guage goes back to the higher reading. Once I begin to slow down or coast in traffic, the reading is near the middle again.

Is this normal or should my oil pump be replaced soon?