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Rats were trained to turn lateral hypothalamic electrical brain stimulation on and off by crossing back and forth in a shuttlebox. Injections of 10 mg/kg morphine doubled the amount of time animals left the stimulation ON without altering OFF times. Tolerance did not develop to this action during 5 daily trials. Injections of 20 mg/kg produced a 4- to 5-fold increase in average ON times together with a large increase in average OFF times. Tolerance did not develop to the ON time increase over 5 daily injections, but did partially develop to the OFF time increase. The ON time increase appears to be based on a mechanism separate from the analgesic action of morphine and from the OFF time increase. Differentiable neurological structures and receptor systems may mediate these actions.
R A Levitt, and
D J Stilwell, and
T M Evers
February 1983,
Pharmacology, biochemistry, and behavior,
R A Levitt, and
D J Stilwell, and
T M Evers
July 1972,
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R A Levitt, and
D J Stilwell, and
T M Evers
April 1977,
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R A Levitt, and
D J Stilwell, and
T M Evers
May 1982,
Pharmacology, biochemistry, and behavior,
R A Levitt, and
D J Stilwell, and
T M Evers
September 1973,
Psychopharmacologia,
R A Levitt, and
D J Stilwell, and
T M Evers
January 1982,
Pharmacology, biochemistry, and behavior,
R A Levitt, and
D J Stilwell, and
T M Evers
July 1983,
The Journal of pharmacology and experimental therapeutics,
R A Levitt, and
D J Stilwell, and
T M Evers
October 1982,
The Journal of pharmacy and pharmacology,
R A Levitt, and
D J Stilwell, and
T M Evers
January 1977,
Science (New York, N.Y.),
R A Levitt, and
D J Stilwell, and
T M Evers
May 1975,
Science (New York, N.Y.),
