Neuropsychobiology 2: 307-312 (1976)
Effects of Repeated Administration of Morphine on Tyrosine Hydroxylase in the Rat Brain1 L. Branchey and A.J. Friedhoff Department of Psychiatry, New York University School of Medicine, New York, N.Y.
Key Words. Morphine ■Reexposure • Tyrosine hydroxylase • Biological memory Abstract. Tyrosine hydroxylase was measured in the caudate of rats subjected to two series of implantations of morphine pellets and in rats subjected to implantations of placebo pellets followed by morphine implantations. The results suggest the existence of a ‘bio logical memory’ for a prior exposure to morphine.
Introduction In previous studies carried out in this laboratory evidence has been found that enzyme systems which change in response to the administration of a drug are more sensitive to a second exposure to the same drug. This occurs even though the drug has been withdrawn long enough to permit the enzyme system to return to normal levels between the two administrations. Friedhoff et al. (1971) have reported that the activity of p-nitroanisole demethylase was higher in the liver of rats exposed to phénobarbital for the second time than in rats exposed for the first time. In another study Friedhoff and Miller (1973) observed a decrease in tyrosine hydroxylase (TH) activity measured in the caudate of rats exposed to ethanol for prolonged period. When rats treated with ethanol were withdrawn for periods sufficient for enzyme levels to return to normal and were then exposed to ethanol a second time, a greater
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 1/1/2019 6:09:34 PM
1 This work was supported by grant number MH08-618 and by Research Scientist Award 14024 to A.J. Friedhoff.
308
Branchey/Friedhoff
Table I. Tyrosine hydroxylase in caudate of rats subjected to one series of implanta tions of morphine pellets
Morphine implanted Control P
n
75 mg
n
225 mg'
8 8
10.88 ±3.72 11.60 ±2.24 NS
7 7
9.74 ±1.26 12.22 ±1.48
Effects of Repeated Administration of Morphine on Tyrosine Hydroxylase in the Rat Brain1 L. Branchey and A.J. Friedhoff Department of Psychiatry, New York University School of Medicine, New York, N.Y.
Key Words. Morphine ■Reexposure • Tyrosine hydroxylase • Biological memory Abstract. Tyrosine hydroxylase was measured in the caudate of rats subjected to two series of implantations of morphine pellets and in rats subjected to implantations of placebo pellets followed by morphine implantations. The results suggest the existence of a ‘bio logical memory’ for a prior exposure to morphine.
Introduction In previous studies carried out in this laboratory evidence has been found that enzyme systems which change in response to the administration of a drug are more sensitive to a second exposure to the same drug. This occurs even though the drug has been withdrawn long enough to permit the enzyme system to return to normal levels between the two administrations. Friedhoff et al. (1971) have reported that the activity of p-nitroanisole demethylase was higher in the liver of rats exposed to phénobarbital for the second time than in rats exposed for the first time. In another study Friedhoff and Miller (1973) observed a decrease in tyrosine hydroxylase (TH) activity measured in the caudate of rats exposed to ethanol for prolonged period. When rats treated with ethanol were withdrawn for periods sufficient for enzyme levels to return to normal and were then exposed to ethanol a second time, a greater
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 1/1/2019 6:09:34 PM
1 This work was supported by grant number MH08-618 and by Research Scientist Award 14024 to A.J. Friedhoff.
308
Branchey/Friedhoff
Table I. Tyrosine hydroxylase in caudate of rats subjected to one series of implanta tions of morphine pellets
Morphine implanted Control P
n
75 mg
n
225 mg'
8 8
10.88 ±3.72 11.60 ±2.24 NS
7 7
9.74 ±1.26 12.22 ±1.48
