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TRANSCRIPT
Chronic treatment and loss of sensitivity to
the In vivo effects of cannabinoids in mice:
differences in mechanism of action
Harinder Singh Spring Semester Rotation
Under the supervision of Dr. Lance McMahon Dept of Pharmacology
UTHSCSA
CANNABIS
Marijuana, Bhang, Ganja, etc
Abuse
Therapeutics
Why Study Cannabis ?
TYPES OF CANNABINOIDS
Δ9-Tetrahydrocannabinol (Δ9-THC), Plant Derived
Anandamide, Brain Derived
CP 55940, Synthetic
CANNABINOID RECEPTORSCB1 CB2
Brain
Lungs
Liver
Kidneys
T-cells
B-cells
Macrophages
Question
Do cannabinoids act through same receptor mechanism to
produce their behavioral effects
Experimental Objective
Chronic treatment with Δ9 THC and examine changes in
sensitivity to Δ9 THC other cannabinoids
Consequences of Chronic Δ9 THC Treatment
• Decrease in receptor density (Rodriguez de Fonesca et al., 1994, Fan et al., 1996)
• Decreased G Protein coupled receptor signaling (Dill and Howlett 1988)
• Reduced sensitivity to the effects of Δ9 THC Tolerance
SPECIFIC AIM
To examine changes in sensitivity to behavioral and physiological effects of Δ9 THC , CP 55940, Anandamide, and a non-cannabinoid (Midazolam) before and during chronic Δ9 THC treatment
Dose
D
urin
g Ch
roni
c TH
C
Befo
re
Anandamide
Effe
ct
Durin
g Ch
roni
c TH
C
Befo
re
Effe
ct
Δ9-THC
Dose
D
urin
g Ch
roni
c TH
C
Befo
re
CP 55940
Effe
ct
Dose
Same MechanismDifferent Mechanism
HYPOTHETICAL DATA
DoseEf
fect
Anandamide
Befo
re
Durin
g C
hron
ic T
HC
Dose
CP 55940
Befo
re
Durin
g C
hron
ic T
HC
Effe
ct
• C57BL/6J male mice (n=7)
• Rectal temperature probe
• Operant conditioning chamber
MATERIAL AND METHODS
Experimental Design
B A A
32 mg/kg Δ9-THC
Δ9-THC
CP 55940
Anandamide
Midazolam
Before Treatment
During Chronic Treatment
AfterTreatment
Doses (mg/kg)
RESULTSBefore Chronic Δ9THC Treatment
Δ9 THC CP 55940 Anandamide Midazolam
Veh 1 3.2 10 17.8 3228
30
32
34
36
38
Veh .032 .1 .32 1 3.228
30
32
34
36
38
Veh 3.2 10 32 56 10028
30
32
34
36
38
Veh 1 3.2 10 32 5628
30
32
34
36
38
Veh 1 3.2 10 17.8 320
25
5075
100125150
Veh .032 .1 .32 1 3.20
25
5075
100125150
Veh 3.2 10 32 56 1000
25
5075
100125150
Veh 1 3.2 10 32 560
25
5075
100125150
Δ: 4°C
Δ: 9°C
Δ: 7°CΔ: 5°C
Tem
pera
ture
(°C
)R
ate
(% c
ontr
ol)
Veh 1 3.2 10 17.8 3228
30
32
34
36
38
Veh .032 .1 .32 1 3.228
30
32
34
36
38
Veh 3.2 10 32 56 10028
30
32
34
36
38
Veh 1 3.2 10 32 5628
30
32
34
36
38
Veh 1 3.2 10 17.8 320
25
5075
100125150
Veh .032 .1 .32 1 3.20
25
5075
100125150
Veh 3.2 10 32 56 1000
25
5075
100125150
Veh 1 3.2 10 32 560
25
5075
100125150
Δ9-THC CP 55940
Doses (mg/kg)
During Chronic Δ9 THC TreatmentTe
mpe
ratu
re (°
C)
Rat
e (%
con
trol
)
Veh 1 3.2 10 17.8 32 5628
30
32
34
36
38
Veh .032 .1 .32 1 3.228
30
32
34
36
38
Veh 1 3.2 10 17.8 32 560
25
50
75
100
125
150
Veh .032 .1 .32 1 3.20
25
50
75
100
125
150
BeforeDuring Chronic Δ9THC
Veh 1 3.2 10 32 5628
30
32
34
36
38
Veh 1 3.2 10 32 56 10028
30
32
34
36
38
Veh 1 3.2 10 32 560
25
50
75
100
125
150
Veh 1 3.2 10 32 56 1000
25
50
75
100
125
150
Anandamide Midazolam
Doses (mg/kg)
Tem
pera
ture
(°C
)R
ate
(% c
ontr
ol)
During Chronic Δ9 THC Treatment
BeforeDuring Chronic Δ9THC
SUMMARY
Drugs Hypothermia Rate of Responding
Δ9 THC Yes Slight
CP 55940 Yes SlightAnandamide NO NO
Midazolam NO NO
Tolerance/Cross-tolerance
CONCLUSIONS
1. CP 55940 effects are mediated by receptor mechanism similar to Δ9 THC
2. a) Anandamide acts at different receptor ?
b) metabolized to non-cannabinoid receptor ligand ?
3. Different cannabinoid mechanisms for hypothermia and decreases in operant responding
FUTURE DIRECTIONS
1. To study specific receptor subtype involved – antagonism studies
2. CB1 and CB2 receptor Knockout mice studies
3. Studies using inhibitors of enzyme metabolizing anadamide
ACKNOWLEDGEMENT
Victoria Carlton
Jesse Usrey
Leah Hargrove
Veronica Sprayberry (Friendly neighbour)
QUESTIONS