INTRODUCTION

Morris water maze was devised by Prof Richard Morris (RGM Morris) 
and described in 1984. It continues to be popular, in fact we think 
its use is increasing, especially with the advent of knockout mice.
It is about place-learning and memory. 

Rats are natural swimmers. They want to get out of the water, but 
swimming does not distress them. Two advantages of Morris water maze 
over others mazes are: 

1. The rat wants to get out, so it searches - it does not wait about.
2. In water there are no local cues (eg scent trails).

(Mice are not so cooperative !)

THE POOL
The Morris water maze consists of a round featureless tank (pool) of water. 
For mice you might use 4-5ft diamter, for rats 5-6ft. The pools supplied
by HVS are 2 ft deep and used with 1 ft of water. The side-wall above the
waterline helps prevent the rodent seeing the pool operator. 
We think it is good to place the pool on a 1-2ft 
base, to make working more convenient(and protect backs !). 

For rats the escape platform can be 4ins (10cms) in diameter. 
The platform should not be too close to the side, or the rat finds it 
just by circling around the pool-side. 
For rats the platform can be 1/4 in below the water. For mice it should 
be very close to the surface.

Usually there are extra-maze cues, to test spatial learning.Roger Morris 
(no connection with Richard Morris) suggests at least 3 cues, which can be 
posters on the wall, with distinctly different patterns. Roger poiunts out that the 
cues should be visible to the rat at the platform, something which one
can overlook !

Is 12ins deep enough ? Reply - "Hi Richard, I've had no problems at all with even 450g rats. 
So in my opinion there should be no problems with 250g rats in 12" (30cm) of water! 
Rats are naturally good swimmers and do not normally sink in a pool!
Hope this helps.Cheers" Franklin Otu, UK


We are told that a good water temperature for rats is 26 deg C +-2 deg. 
Colder encourages activity but can cause hypothermia which impairs 
learning.