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

1
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
Figure 1
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).
Results Acquisition All rats met the acquisition
criterion. As seen in Figure 2, there were no
significant differences between groups in latency
to find FLs during any trials (Trial 1
F(3,17).826, pgt.05 Trial 2 F(3,17)1.440,
pgt.05 Trial 3 F(3,17)1.201, pgt.05 Trial 4
F(3,17)1.017, pgt.05 Trial 5 F(3,17)1.436,
pgt.05 Trial 6 F(3,17)1.031, pgt.05). Testing As
shown in Figure 3, there were no significant
differences between groups in total quadrant
preference on the probe trial test (F(3,17).367,
pgt.05). In addition, none of the groups differed
from chance on the test trial (WIN/WIN
t(6)-1.360, pgt.05 WIN/VEH t(6).428, pgt.05
VEH/WIN t(2)-.240, pgt.05 VEH/VEH t(3)-.594,
pgt.05).
Day 1 Shaping
Trial 1 Exposed Trial 2 Partially Exposed
Day 2 Training
Trial 3 Partially Buried Trial 4 Shallow Buried
Table 1
Day 3 Training
Training
Trial 5 Buried Trial 6 Deep Buried
WIN/WIN (n7) SDR VEH/WIN (n3) Control
WIN/VEH (n7) Amnesia VEH/VEH (n4) Control
Testing
Day 10 Testing
Probe Trial No FL
2
Figure 2
Method Subjects The subjects were 90-day old,
male Long-Evans rats (N21). Rats were reduced
to and maintained at 85 of their free-feeding
weights one week prior to and during the
experiment. Rats were maintained on a 12-hour
light/dark cycle. 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 Froot Loops cereal (FL),
which was 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
for one week prior to shaping. A three-day
procedure was used with two trials per day, which
including shaping, training, and testing (see
Figure 1). Prior to shaping, rats were randomly
assigned to groups which determined whether they
received an injection of WIN-2 (3.0 mg/kg) or VEH
during training and testing (See Table 1). Rats
received intraperitoneal (I.P.) injections of
WIN-2 (3.0 mg/kg) or VEH 30 minutes prior to
training and testing. Latency to find the FL was
measured during acquisition, rats were required
to find the FLs within 10 minutes of the start of
the trial in order to meet the acquisition
criterion. Once acquisition criterion was met,
rats received a test trial in which no FL were
buried in the maze. Latency to dig and quadrant
preference were measured during videotaped test
trials.

• Discussion
• All rats performed to the same degree during
  shaping and training.
• None of the groups exhibited memory for the task
  during testing, regardless of drug
  administration.
• Lack of memory may be due to the training
  procedure employed, specifically massed training
  trials
• Trial Spacing Effect Kraemer Randall (1985)

• 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.  
• Kraemer, P. J., Randall, C. K. (1985). Spatial
  learning in preweanling rats trained in a Morris
  water maze. Psychobiology, 23(2), 144-152.
• 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.
• Spear, N. E. Riccio, D. C. (1994). Memory
  Phenomena and Principles. Boston Allyn Bacon.

Figure 3