CONDITIONED PLACE PREFERENCE IN MICE

EXPOSED TO WEAK LOW FREQUENCY MAGNETIC

FIELDS

By Mansur MulkMEDBIO 3970Z

OUTLINE Definition. Possible application. Theory. Instrumentation. CPP Experiment. Experimental Results. Conclusion Advantages and Limitation.

WHAT IS CPP? Condition Place Preference is an environmental place

conditioning procedure which is a commonly used technique to model the condition reinforcing effect of drugs in experimental animals. It is the pairing between a novel environmental stimulus (place) and a reflex-eliciting stimulus (drug or in this case PLFMF). This paradigm is traditionally used to determine if

stimuli are rewarding. Conditioning a mouse to a novel environment is

conducted by singly or repeatedly placing it in a new environment while exposing it to a drug or PLFMF. If the stimulus is positive the mouse will choose

that environment when given a choice. If the stimulus if negative the opposite effect will

be observed.

POSSIBLE APPLICATIONS:

  A lot of information is present in a Condition Place Preference environment.

Anti Depression Drug. Protective Role of High Blood Pressure on pain

Complaints in the population.(Hagen et. Al., 2005) Magnetotherapy, employing static magnetic fields,

millimetre waves and specific pulsed magnetic fields.(Radzievsky et. al., 2000).

CONDITION PLACE PREFERENCE(CPP)WHEN EXPOSED TO PULSE LOW FREQUENCY MAGNETIC FIELD

Pain and Nociception:(C. Del Seppia et al. 2007)

“An unpleasant sensory or emotional experience associated with actual or potential tissue dmage”(Merskey, 1983)

Increase in Pain Sensitivity: in Snails(Kavaliers, 1988)

Increase or Decrease in Pain Sensitivity: Various combination of dynamic and static fields

(Prato et al., 2000)

Reduce thermal nociception in:

Snails (Thomas et al., 1997)

Mice (Shupak et al., 2004)

Humans (Shupak et al., 2004)

Influence the vestibular system in:

Humans (Thomas et al., 2001

PLFMF used in this study. The discontinuous 60 Hz field was identical except for the sinusoidal form in place of the box-like wave (refractory period identical in both). Yves Bureau, PhD, March 6, 2009

INSTRUMENTATION

CPP apparatus and magnetic field generator. Helmholtz coils surround the individual boxes.

Conditioned place preference (CPP) apparatus.

THE ASSUMPTION 1.PLFMF like many narcotics reduce sensation to pain in mice.2.Narcotics such as morphine easily condition mice to prefer one environment over another.3.PLFMF can also successfully be used to condition mice.

Attempted to condition mice to prefer one novel box over another using morphine and PLFMF.

EXPERIMENT DESIGN

1) Saline injected mice2) Sham (magnetic field generator is turned on but there is not power to the coils)3) 5 mg/kg of morphine sulfate.4) Complex Neuroelectromagnetic Pulse (Cnp)5) 60 Hz pulse which is equivalent to the Cnp with respect to refractory periods in the pulse.

GROUP MEMBERSHIP

PROTOCOL 1. Mice were first habituated to a conditioned place

preference apparatus.2. Following habituation, the amount of time mice spent in

either box or the bridge for a 15 minute session was recorded.

3. For the next 10 days mice were confined for 30 minutes per day every second day to the box they preferred least while being exposed to either: 1. Morphine (5 mg/kg)2. Saline or Sham magnetic field (Control)3. Cnp4. 60 Hz

4. On the alternate days mice were exposed to either saline if drug injected or to a sham magnetic field condition if exposed to PLFMF while in the preferred box.

5. On the test day the mice were given the choice of spending time in either the preferred or non-preferred box for 15 minutes.

STATISTICS

A mixed analysis of variance was conducted with pre/post conditioning and box type as the within subject variable and treatment as the between subject variable. Simple simple main effect analysis was conducted for condition at the non preferred box post conditioning. All results were considered significant when the probability of making a Type 1 error was less that 5% (p<.05). All results were interpreted using the Greenhouse Geisser correction.

RESULTS

  1. There was a tendency toward a pre/post conditioning by box type by treatment interaction, (F(5,74)=1.8, p=.120) (Figures 1a, 1b). Due to sample size this effect was not significant. 2. However, a simple simple main effect analysis on treatment at the non preferred boxes post conditioning was conducted in spite of this negative result. A significant group difference was observed (F(3,43)=2.96, p<.05). 3.A post hoc Tukey test did not show any differences suggesting that the simple simple main effect was due a combination of treatment groups that differed from the control group. 4.All-in-all the control group was different from all the treatment groups combined (Figure 1b).

RESULTS SHOWING TIME SPENT IN EITHER THE PREFERRED, NON-

PREFERRED, OR BRIDGE CONNECTING THE BOXES

Tim

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0200

250

300

350

400

450

500

Control 60 Hz Cnp Morphine

Tim

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150

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Control 60 Hz Cnp Morphine

Figures 1a: Time spent in either the preferred, neutal (bridge), or non preferred box prior to conditioning.

Figures 1b: Time spent in either the preferred, neural (bridge), or non preferred box and after condition using Morphine, Cnp, 60 Hz, or Saline.

Time Spend Before Conditioning Time spend after

Conditioning

CONCLUSIONS

Box paired with stimulus produced conditioning effect.

In order to have an optimistic result sample size should be 15 individual per group.

ADVANTAGES:

Tests animals in a drug-free state. Sensitive to both reward and aversion. Allows for simultaneous determination of CPP and neuron

activity. Adaptable to a variety of species; Utility in probing the neural circuits involved in drug reward.

LIMITATIONS1.Subject to interpretation based on the notion of novelty seeking. 2.Difficult to interpret when animals prefer one context prior to drug conditioning. 3.lacks face validity as an experimental protocol of drug reward in humans.

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