Examination of the State Dependent Properties of WIN-55-212-2 on Spatial Learning and Memory in Rats in the Sand Maze

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Examination of the State Dependent Properties of
WIN-55-212-2 on Spatial Learning and Memory in
Rats in the Sand Maze   Ashley R. Smith and
Gretchen Hanson Gotthard Randolph-Macon Womans
College Lynchburg, VA 24503
Results No differences in latency were exhibited
between groups on Day 1 however, differences
emerged on the first day of training when rats
received WIN-2. Overall quadrant preference did
not differ between groups, but a breakdown of
quadrant preference by minutes revealed poorer
performance in the different state group than in
the same state groups. Acquisition As can be
seen in Figure 1, latency did not differ between
groups on Day 1 Shaping Trial 1, F(2,14)
0.150, p gt .05, and Trial 2, F(2,14) 1.146, p gt
.05. Rats only differed on the first day of
drug administration Trial 3, F(2,14) 3.563, p
.05. That is, rats receiving WIN-2 showed
longer latencies to find the reward than rats
receiving vehicle injections on the first
training trial. Quadrant Preference As can be
seen in Figure 2, there were no differences in
overall quadrant preference between the groups
F(2,14) 1.239, p gt .05. However, as seen in
Figure 3, a breakdown of quadrant preference by
minutes showed significant differences between
the groups during Minute 1 F(2,14) 4.794, p lt
.05 and Minute 4 F(2,14) 4.231, p lt .05. An
LSD post hoc analysis showed that the different
state group spent significantly less time (p lt
.05) in the correct quadrant than the same state
groups. The different state group showed a
quadrant preference that was significantly below
chance during Minute 4 t(5) 3.043, p lt .05
and Minute 10 t(5) -2.632, p lt .05 of the
probe trial which would indicate a place aversion
to the correct quadrant.
Introduction Naturally occurring cannabinoids
(e.g., THC) and synthetic cannabinoids (e.g.,
WIN-55-212-2), have been linked with hippocampal
function, and therefore, spatial learning and
memory. Although a number of studies have shown
a relationship between cannabinoid administration
and learning and memory deficits (e.g., Lichtman,
et al., 1995), no studies have explicitly
examined the state dependent properties of
synthetic cannabinoids. State dependent
retention refers to the tendency of organisms to
recall information better when in the same
state they were in during learning, than if
they were in a different state during learning
and testing (Spear and Riccio, 1994). In fact, if
cannabinoid administration produces state
dependent effects, then a memory impairment
following cannabinoid administration may not be
due to decreased hippocampal function alone, but
may be due to an altered state between
acquisition and training or testing. The critical
test for state dependent retention is to return
the subject to the original state to determine if
an inaccessible memory can be retrieved. The
sand maze was used in the present study, and is
an appetitive open-field spatial task that may
serve as an alternative to the water maze in some
studies. While the water maze requires rats to
swim in a pool of water to locate a hidden
platform (Morris, 1981), the sand maze requires
rats to dig in a pool of sand to retrieve buried
cereal rewards (Hanson, 2003). The sand maze may
be a better alternative for studies that aim to
examine spatial behavior without the potential
side effects of aversive tasks (e.g., increased
amygdala activity and/or fight or flight
responses). The state dependent properties of
the synthetic cannabinoid WIN-55-212-2 (WIN-2)
were examined in the present study using the sand
maze. It was hypothesized that any deficit
produced by WIN-2 during training would be
diminished by returning the subject to the
original learning state during testing (i.e., no
drug).
Figure 1
Figure 2

• Discussion
• All rats performed equally well during shaping.
• Rats in the same state groups preferred the
  correct quadrant more than rats in the different
  state group.
• Rats in the different state group appeared to
  exhibit a place aversion for the correct
  quadrant.
• Robinson, et al., 2003
• Future research might examine the state dependent
  properties of WIN-2 with a lower dose of the drug
  (e.g., 3 mg/kg) to reduce the possible
  aversiveness produced by larger doses.

Method Subjects The subjects were 90-day old,
male Long-Evans rats (N20). Rats were reduced
to and maintained at 85 of their free-feeding
weights one week prior to and during the
experiment. Water was available ad
libitum. Apparatus The sand maze was a plastic
pool (36 inches wide by 6 inches deep) filled
with a sand/crushed Froot Loops (FL) cereal
mixture that was 2 inches deep (approximately 11
ounces of FL was crushed and mixed with 100
pounds of play sand to make the mixture). The
maze was elevated 36 inches off the floor.
Procedure Each rat was placed in the sand maze
and required to find FL, which were located in
one consistent location during shaping and
training (i.e., NW, NE, SW, or SE quadrant).
Rats were started from a different location in
the maze on each trial (i.e., N, S, E, or W).
After finding the reward on any given trial, the
rat was allowed to consume approximately three to
four FL prior to termination of the trial.
Rats were handled prior to shaping. A
three-day procedure was used with two trials per
day, which included shaping, training, and
testing (see Table 1). Rats were randomly
assigned to groups that determined whether they
were injected with WIN-2 (5.6 mg/kg) or VEH
during training and testing (see Table 1). Rats
received intraperitoneal (I.P.) injections of
WIN-2 (5.6 mg/kg) or VEH 30 minutes prior to
training and testing trials. Latency to find the
reward was measured during acquisition. Latency
to dig and quadrant preference were measured
during videotaped test trials.
References Hanson, G.R. (2003).  The sand maze
An appetitive alternative to the Morris water
maze (Doctoral dissertation, Kent
State University, 2003). Dissertation Abstracts
International, 63, 4958.   Lichtman, A.
H., Dimen, K. R., Martin, B. R. (1995).
Systemic or intrahippocampal
cannabinoid administration impairs spatial memory
in rats. Psychopharmacology,119(3),282-
290. Morris, R.G.M. (1981). Spatial
localization does not require the presence of
local cues. Learning and Motivation,
12, 239-260. Robinson, L., Hinder, L., Pertwee,
R. G., Riedel, G. (2003). Effects of Delta-9-
tetrahydrocannabinol and WIN-55,212-2 on
place preference in the water maze in rats.
Psychopharmacology, 166, 40-50. Spear, N. E.
Riccio, D. C. (1994). Memory Phenomena and
Principles. Boston Allyn Bacon.
Figure 3
Table 1
Day 1 Shaping Trial 1 Exposed Trial 2 Partially Buried Day 2 Training Trial 3 Shallow Buried Trial 4 Buried (Shallow) Day 3 Training Trial 5 Buried (Medium) Trial 6 Buried (Deep) ? Day 10 Testing Probe Trial (No Reward Buried in the Sand)
Different State (n6) No drug WIN-2 WIN-2 WIN-2
Same State (n5) No drug WIN-2 WIN-2 VEH
Same State (n9) No drug No drug No drug No drug