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Narcotic analgesics and the regulation of neuronal catecholamine stores
Frontiers in Catecholamine Research
xxi
NARCOTIC ANALGESICS AND THE REGULATION OF NEURONAL CATECHOLAMINE STORES E. Costa, A. Carenzi, A. Guidotti and A. Revuelta Laboratory of Preclinical Pharmacology, NIMH, Saint Elizabeths Hospital, Washington D.C ., U.S .A . An involvement of catecholaminergic neurons has been advocated in explaining the action of narcotic analgesics . This involvement was inferred from changes in the incorporation of radioactive tyrosine into brain catecholamines caused by morphine (Clouet and Ratner, Science 168: 854, 1970 ; Smith et al ., Science 170: 1106, 1970 ; Rosenman and Smith, Nature 240: 153, 1972 ; Rethy et al., . J . Pharmacol . exp. Ther . 176: 472, 1971 ; Smith et al.,. J. Pharmacol. exp. Ther. 180: 547, 1972 ; Loh et al., . Life Sci. 12 : 33, 1973 The present study deals with a measurement of turnover rate of dopamine (DM) in striatum, and norepinephrine (NE) in cerebellum and spinal cord of rats receiving various doses of morphine (from 2 .5 to 20 mg/kg i.p.) administered acutely or chronically . Chronic administration of morphine was performed by pellet implantation (Ho et al ., J. Pharmacol. exp. Ther . 182: 155, 1972). Rats were pulse labeled with 3, 5' -'H tyrosine (500 to 1000 E.r.c/kg, S.A . 30 Ci/mmole) ; NE, DM, Dope, and tyrosine specific radioactivity was measured in the same tissue sample after tissue extract purification by ion exchange column chromatography and A1,0, adsorption ; turnover rate of NE or DM was measured from the initial rates of radio-activity incorporation by applying principles of steady state kinetics . The turnover rate measurements were performed in tissues that contain only terminal axons of only one type of catecholaminergic neurons. The analgesic AD,o of morphine administered intraperitoneally was about 20 mg/kg, this dose of morphine is about threshold to cause an increase of the turnover rate (nmoles/g/hr) of striatal DM (from a rate 15 ± 1 .3 to 25 ± 2.5). In the same animals, doses even greater of morphine fail to change the turnover rate of cerebellar or spinal cord NE . The selectivity of the morphine action on striatal DM turnover rate is in keeping with recent reports on the location of the opiate receptor in nervous tissue (Pert and Snyder, Science 179: 1011, 1973). Rats chronically implanted with morphine pellets have no alterations of the catecholamine turnover rate in the three brain areas mentioned above. When intraperitoneal doses of morphine (from 20 to 160 mg/kg i.p.) are inj ected into rats made tolerant to morphine the turnover rate of striatal DM is again selectively increased but the doses required are about four fold that of normal rats . The rats implanted with morphine pellets are tô be considered morphine dependent according to thenaloxone test . . Naloxone in doses of 32 mg/kg i.p . increased the turnover rate of striatal DM ; smaller doses (4, 8 and 16 mg%kg) were inactive on striatal DM turnover . Also, naloxone in the doses rested failed to change NE turnover rate in cerebellum and spinal cord . Viminol or 1-(a}(N-O-chlorbenzyl}pyrryl~l-di sec butylamine ethanol
axü
Frwitiera in Catecholamine Research
p~ydroxybenzoate, is a central analgesic (Dells Bells, Boll . Chim . Farm. 111 : 5. 1972) which exhibits cross tolerance to morphine . This copipound possesses three asymmetric carbon atoms and thus there are six possible seric configurations of vimïnol. The analgesic activity resides in the R2 stereoisomer . Viminol (R,), like morphine, selectively increases the turnover rate of striatal DM without affecting the turnover rate of cerebellar or spinal cord NE . The dose which increases DM turnover rate is about 2 .5 mg/kg, this dose is about AD for analgesia. The S, stereoisomer is devoid of analgesic activity but antagonizes the analgesic effect of R but not that of morphine . However, viminol S, can antagonize the effects of chronic administration of morphine end R~ . When a maximal tolerated dose of S, (20 mg/kg i.p.) is inj acted into rats the turnover rate of striatal DM or of cerebellar and spinal cord NE is unchanged. Therefore, S, differs from naloxone because it does not antagonize morphine analgesia and it does not change DM turnover . Morphine increases the cyclic 3' , 5' -AMP (CAMP) concentrations of adrenal cortex, adrenal medulla and anterior pituitary but it does not change the concentration of this nucleotide in striatum, cerebellum and hypothalamus . The increment of cAMP elicited by morphine in adrenal medulla persists longer than four hours and at peak intensity the accumulation is greater than 5-fold in pituitary, adrenal cortex and medulla . The increase of medullary cAMP elicited by morphine correlates with a delayed appearance of an increase of tyrosine hydroxylase activity in adrenal medulla. In animals receiving 50 mg/kg of morphine i.p ., the tyrosine hydroxylase activity of brain stem, striatum, hypothalamus and denervated adrenal is unchanged. Rats implanted with morphine pellets, show no changes in cAMP concentrations or tyrosine hydroxylase in adrenal medulla. The response of adrenal medulla cAMP concentrations and tyrosine hydroxylase activity to cold exposure in rats chronically implanted with morphine will be reported . ONTOGENETIC REGULATION OF CATECHOLAMINE SYNTHESIS Joseph T. Coyle, Jr . National lnatitute of Mental Health,Betheeda, Md . 20014, U .3 .A .
Histologic studies indicate that the maj or nuclei of the central catecholaminergic neurons of the rat are formed well before birth whereas the outgrowth of their axons and terminals occurs primarily during the four weeks after birth.; In the whole brain during this period, there is a marked increase in the activity of the specific uptake mechanism for norepinephrine, a process associated with the nerve terminals . The activities of the enzymes involved in the biosynthesis of catecholamines, tyrosine hydroxylese (EC 1.14.3a), DOPA decarboxylase (EC 4.1 .1 .26) and dopamine-/.~-hydroxylase (EC 1 .14.2 .1) increase 500-fold per neuron during maturation . Concurrently, there is a centrifugal movement of these enzymes from the regions of the brain that contain the catecholaminergic cell bodies to the regions that receive the terminals as well as an increase in the
xxi
NARCOTIC ANALGESICS AND THE REGULATION OF NEURONAL CATECHOLAMINE STORES E. Costa, A. Carenzi, A. Guidotti and A. Revuelta Laboratory of Preclinical Pharmacology, NIMH, Saint Elizabeths Hospital, Washington D.C ., U.S .A . An involvement of catecholaminergic neurons has been advocated in explaining the action of narcotic analgesics . This involvement was inferred from changes in the incorporation of radioactive tyrosine into brain catecholamines caused by morphine (Clouet and Ratner, Science 168: 854, 1970 ; Smith et al ., Science 170: 1106, 1970 ; Rosenman and Smith, Nature 240: 153, 1972 ; Rethy et al., . J . Pharmacol . exp. Ther . 176: 472, 1971 ; Smith et al.,. J. Pharmacol. exp. Ther. 180: 547, 1972 ; Loh et al., . Life Sci. 12 : 33, 1973 The present study deals with a measurement of turnover rate of dopamine (DM) in striatum, and norepinephrine (NE) in cerebellum and spinal cord of rats receiving various doses of morphine (from 2 .5 to 20 mg/kg i.p.) administered acutely or chronically . Chronic administration of morphine was performed by pellet implantation (Ho et al ., J. Pharmacol. exp. Ther . 182: 155, 1972). Rats were pulse labeled with 3, 5' -'H tyrosine (500 to 1000 E.r.c/kg, S.A . 30 Ci/mmole) ; NE, DM, Dope, and tyrosine specific radioactivity was measured in the same tissue sample after tissue extract purification by ion exchange column chromatography and A1,0, adsorption ; turnover rate of NE or DM was measured from the initial rates of radio-activity incorporation by applying principles of steady state kinetics . The turnover rate measurements were performed in tissues that contain only terminal axons of only one type of catecholaminergic neurons. The analgesic AD,o of morphine administered intraperitoneally was about 20 mg/kg, this dose of morphine is about threshold to cause an increase of the turnover rate (nmoles/g/hr) of striatal DM (from a rate 15 ± 1 .3 to 25 ± 2.5). In the same animals, doses even greater of morphine fail to change the turnover rate of cerebellar or spinal cord NE . The selectivity of the morphine action on striatal DM turnover rate is in keeping with recent reports on the location of the opiate receptor in nervous tissue (Pert and Snyder, Science 179: 1011, 1973). Rats chronically implanted with morphine pellets have no alterations of the catecholamine turnover rate in the three brain areas mentioned above. When intraperitoneal doses of morphine (from 20 to 160 mg/kg i.p.) are inj ected into rats made tolerant to morphine the turnover rate of striatal DM is again selectively increased but the doses required are about four fold that of normal rats . The rats implanted with morphine pellets are tô be considered morphine dependent according to thenaloxone test . . Naloxone in doses of 32 mg/kg i.p . increased the turnover rate of striatal DM ; smaller doses (4, 8 and 16 mg%kg) were inactive on striatal DM turnover . Also, naloxone in the doses rested failed to change NE turnover rate in cerebellum and spinal cord . Viminol or 1-(a}(N-O-chlorbenzyl}pyrryl~l-di sec butylamine ethanol
axü
Frwitiera in Catecholamine Research
p~ydroxybenzoate, is a central analgesic (Dells Bells, Boll . Chim . Farm. 111 : 5. 1972) which exhibits cross tolerance to morphine . This copipound possesses three asymmetric carbon atoms and thus there are six possible seric configurations of vimïnol. The analgesic activity resides in the R2 stereoisomer . Viminol (R,), like morphine, selectively increases the turnover rate of striatal DM without affecting the turnover rate of cerebellar or spinal cord NE . The dose which increases DM turnover rate is about 2 .5 mg/kg, this dose is about AD for analgesia. The S, stereoisomer is devoid of analgesic activity but antagonizes the analgesic effect of R but not that of morphine . However, viminol S, can antagonize the effects of chronic administration of morphine end R~ . When a maximal tolerated dose of S, (20 mg/kg i.p.) is inj acted into rats the turnover rate of striatal DM or of cerebellar and spinal cord NE is unchanged. Therefore, S, differs from naloxone because it does not antagonize morphine analgesia and it does not change DM turnover . Morphine increases the cyclic 3' , 5' -AMP (CAMP) concentrations of adrenal cortex, adrenal medulla and anterior pituitary but it does not change the concentration of this nucleotide in striatum, cerebellum and hypothalamus . The increment of cAMP elicited by morphine in adrenal medulla persists longer than four hours and at peak intensity the accumulation is greater than 5-fold in pituitary, adrenal cortex and medulla . The increase of medullary cAMP elicited by morphine correlates with a delayed appearance of an increase of tyrosine hydroxylase activity in adrenal medulla. In animals receiving 50 mg/kg of morphine i.p ., the tyrosine hydroxylase activity of brain stem, striatum, hypothalamus and denervated adrenal is unchanged. Rats implanted with morphine pellets, show no changes in cAMP concentrations or tyrosine hydroxylase in adrenal medulla. The response of adrenal medulla cAMP concentrations and tyrosine hydroxylase activity to cold exposure in rats chronically implanted with morphine will be reported . ONTOGENETIC REGULATION OF CATECHOLAMINE SYNTHESIS Joseph T. Coyle, Jr . National lnatitute of Mental Health,Betheeda, Md . 20014, U .3 .A .
Histologic studies indicate that the maj or nuclei of the central catecholaminergic neurons of the rat are formed well before birth whereas the outgrowth of their axons and terminals occurs primarily during the four weeks after birth.; In the whole brain during this period, there is a marked increase in the activity of the specific uptake mechanism for norepinephrine, a process associated with the nerve terminals . The activities of the enzymes involved in the biosynthesis of catecholamines, tyrosine hydroxylese (EC 1.14.3a), DOPA decarboxylase (EC 4.1 .1 .26) and dopamine-/.~-hydroxylase (EC 1 .14.2 .1) increase 500-fold per neuron during maturation . Concurrently, there is a centrifugal movement of these enzymes from the regions of the brain that contain the catecholaminergic cell bodies to the regions that receive the terminals as well as an increase in the