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Noradrenaline and ethanol intake in the rat
Neuroscience Letters, 12 (1979) 137--142 © Elsevier/North-Holland Scientific Publishers Ltd.
137
N O R A D R E N A L I N E A N D ETHANOL INTAKE IN THE RAT
S T E P H E N T. M A S O N , M I C H A E L
E. C O R C O R A N *
and H A N S C. FIBIGER
Division of Neurological Sciences, Department of Psychiatry, University of British Columbia, Vancouver V 6 T 1 W 5 (Canada) (Received December 6th, 1978) (Revised version received December 27th, 1978) (Accepted December 27th, 1978)
SUMMARY
Intracerebral injection of 4 pg of the neurotoxin 6-hydroxydopamine (6-OHDA) was used to deplete forebrain noradrenaline (NA) in rats to less than 5% of control values without affecting brain dopamine (DA) and the oral consumption of ethanol examined. Control rats showed a progressive increase in their intake of a 15% ethanol solution and after 15 days were consuming large quantities. This increase did n o t occur in NA depleted rats, which after 15 days had consumed no more than a few miUilitres of the solution in total. The results are discussed in terms of a central noradrenergic basis of ethanol reward.
A number of studies have implicated catecholaminergic mechanisms in the mediation of some of the pharmacological effects of ethanol. Thus, injection of the catecholamine synthesis inhibitor, alpha-methyl-para-tyrosine (AMPT) prevented the usual m o t o r excitation induced by ethanol [ 5], and has been reported to reduce its euphoric effects in humans [ 1 ]. Destruction of catecholaminergic neurones by intraventricular injection of the neurotoxin 6-hydroxydopamine (6-OHDA) has been shown to alter the patterns of oral consumption of ethanol solutions in rats [10,15]. The weakness with previous studies has generally been that no distinction between noradrenaline (NA) and the related catecholamine dopamine (DA) has been made. Thus, AMPT affects the synthesis of both amines and intraventricular 6-OHDA can damage both systems unless additional manipulations are used. Brown and Amit [3] did relate their results to 6-OHDA-induced depletion of NA alone, b u t the anatomical locus of the effect is unclear. Their intraventricular 6-OHDA injections would be expected to result in widespread depletion of NA throughout *Present address: Department of Psychology, University of Victoria, Victoria, B.C. V8W 2Y2 (Canada).
138
the forebrain, cerebellum and spinal cord. We sought to demonstrate a role for the noradrenergic innervation of the forebrain in ethanol consumption by using injections of 6-OHDA into the ascending NA fibre bundle in the mesencephalon that would n o t affect DA systems. 10 male albino Wistar rats (Woodlyn Farms, Ontario) weighing 300 g at the time of operation were anaesthetised with Nembutal (50 mg/kg, intraperitoneal) and positioned in a stereotaxic apparatus. T w o holes were drilled in the skull through which a 34 gauge cannula was lowered bilaterally to the following coordinates: AP ÷ 2.6 mm from interaural line, ML -+ 1.1 mm from midline suture at bregma and DV + 3.7 mm from interaural line [11]. 4 pg of 6-OHDA HBr (Regic Chemicals, weight expressed as free base) dissolved in 2 pl of 0.9% saline with 0.3 mg/ml ascorbic acid antioxidant were infused at the rate of 1 pl/min over 2 min and the cannula was left in place for a further minute to permit diffusion of the drug. The skin was then sutured and 2 weeks were allowed to permit anterograde degeneration of forebrain NA terminals before behavioural testing c o m m e n c e d [ 17 ]. 9 control rats received similar injections of salineascorbate vehicle only. Daily intake of water was measured by the use of the t w o graduated Richter tubes attached to the animal's home cage. After 5 days of water intake a choice was offered between one tube containing 15% ethanol solutions (v/v) and another containing water. These choice days were then alternated with days in which both tubes contained water so as to avoid the effects of dehydration or alteration in fluid balance. Water and ethanol intake was recorded for 15 days of ethanol versus water choice. Following completion of behavioural testing all animals were sacrificed by cervical fracture. Their brains were rapidly removed and dissected on ice as described elsewhere [ 16] into the following regions: hippocampus, cortex, hypothalamus and striatum. These areas were weighed and homogenised in TABLE I POST-MORTEM AMINE ASSAYS V a l u e s are m e a n s + S.E.M. in ng o f amine per g w e t w t . o f tissue. The % c o l u m n is the perc e n t a g e o f c o n t r o l c o n c e n t r a t i o n s remaining in l e s i o n e d tissues.
Controls ( n = 9) NA Hippocampus Cortex Hypothalamus
3 0 5 -+ 18 2 8 9 +- 14 2 3 8 0 -+ 1 1 0
DA Striatum Hypothalamus
1 3 , 6 0 0 -+ 6 6 0 4 5 2 -+ 19
Lesioned ( n = 10)
15 -+ 9 +8 6 0 *-
%
3 6 90
5 3 36
1 2 , 9 0 0 +- 1 2 3 0 421 _+ 26
95 93
139
0.1 N perchloric acid and the endogenous catecholamine c o n t e n t was assayed by the m e t h o d of McGeer and McGeer [14]. This served to confirm that the 6-OHDA injection had produced the expected pattern and extent of amine depletion. The biochemical data shown in Table I indicate that severe and permanent destruction of forebrain noradrenaline neurones occurred. Thus, hippocampal and cortical NA was reduced to less than 5% of control values and marked, but less severe, damage occurred to the hypothalamic innervation, with the NA c o n t e n t being reduced to some 35% of control. No significant alteration in brain dopamine was found with this treatment. The ethanol intake on alternate days of free-choice between 15% (v/v) ethanol solution and water is shown in Fig. 1 for the control and NA-depleted rats. It can be seen that control rats gradually increased their intake over the 15 days so that by the end of this period quite considerable volumes of ethanol solution (mean = 12 ml) were being consumed. The NA-depleted rats, however, failed to increase their intake, and apart from occasional sampling of the ethanol solution, failed to consume more than a few millilitres of it over the entire 15-day period. The total volume of ethanol solution consumed
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o f a 1 5 % ethanol solution (v/v) over 15 days of free-choie between ethanol and water for 10 NA-depleted rats and 9 vehicle injected controls, o D, controls, n = 9 ; m - - - - - - m t r e a t e d , n = 1 0 Fig. 1. Consumption
140
over 15 days is shown in Fig. 2 as a scatter diagram and it can be seen that NA depleted rats tended to drink very little and cluster towards the bottom left-hand comer of the graph, whereas the control rats consumed large volumes (sometimes in excess of 100 ml in toto) and so cluster towards the upper right-hand corner with very little overlap between the two groups. Statistical analysis confirmed the significance of the difference. Thus, the MannWhitney U-test [18] on the total ethanol intake over 15 days revealed a U-value of 10.5,P < 0.01. A two-factor repeated measures analysis of variance [ 19] applied to the daily intake showed that the control and lesioned animals were slgmficantly ditferent (between groups F (1, 17) = 8.53, P < 0.01 and group by days interaction F { 1 4 , 2 3 8 ) = 3.70, P < 0.001). Water intake, both between ethanol days and on the water tube in the
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Fig. 2. Scatter diagram s h o w i n g total c o n s u m p t i o n o f 15% ethanol solution (v/v) over 15 days o f free-choice for 10 N A - d e p l e t e d and 9 vehicle injected rats. ~, controls, n = 9; , , treated, n = 10.
141
ethanol-water choice days, did n o t differ between control and lesioned rats. This is in accord with previous observations [ 1 2 ] . Spontaneous l o c o m o t o r activity of these same animals measured in photocell cages also failed to differ, again consistent with previous reports [ 1 6 ] . The changes in ethanol intake do n o t therefore appear to be secondary to a reduced water-intake or a general lethargy induced by the lesion. The results of this experiment indicate that catecholamines are indeed involved in the voluntary ingestion of ethanol solutions by rats. Depletion of forebraln NA to less than 5% of control values completely prevented the usual, sometimes quite copious, intake of ethanol seen in controls. The experim e n t further indicates that the catecholamine of importance is NA, since loss of brain NA, without any effect on dopamine, was adequate to alter ethanol intake. This thus extends and refines previous work [ 1,3,10,15] suggesting a role of catecholamines in the pharmacological effects of ethanol. The mechanism by which the NA depletion acts to reduce ethanol intake is uncertain. It has been suggested that NA neurones serve a critical role of central reward [6,7] and this has been generalised to include ethanol-reward [2--4]. Since additional work has questioned the involvement of NA in reward generated by food, electrical stimulation of the brain, water, or negative reinforcers such as electric foot-shock or taste aversion paradigms (for review see refs. 9 and 13) it seems less justifiable to invoke a NA system in the reward aspect of ethanol ingestion. A perseveration of responding during withdrawal of reward (in extinction) has been demonstrated after NA depletions (for review see ref. 13) and this inflexibility in altering behaviour might explain the failure of the NA depleted group to increase their ethanol intake in the present experiment. We have preliminary evidence that NA depletion does n o t affect either the 'sensitivity' of the rat to the unpleasant taste of ethanol or the pharmacologically aversive properties of the drug as measured in a taste aversion paradigm, t w o other factors which would be expected to be of importance in determining the amount of ethanol solution consumed voluntarily. Thus, it is n o t immediately clear why NA depletion should reduce the self-administration of ethanol. As a first step in clarifying this, it would be useful to examine the effects of NA depletion on other actions of ethanol and on self-administration in other experimental situations. The clinical relevance of the present study is shown by the use of the noradrenaline synthesis inhibiting drug Antabus ® in the treatment of alcoholism [2--4] and by suggestions of a role for brain NA in other behavioural disorders [ 8 ] .
ACKNOWLEDGEMENTS
The work was supported by the MRC and S.T.M. is in receipt of an MRC Fellowship. The able technical assistance of Betty Richter is gratefully acknowledged.
142 REFERENCES 1 Ahlenius, S., Carlsson, A., Engel, J., Svensson, H. and Sodersten, P., Antagonism by alpha-methyl-para-tyrosine of the ethanol-induced stimulation and euphoria in man, Clin, Pharmacol. Ther., 14 (1973) 586--591. 2 Amit, Z., Brown, W., Levitan, D.E. and Ogren, S.-O., Noradrenergic mediation of the positive reinforcing properties of ethanol. I. Suppression of ethanol in laboratory rats following dopamine-beta-hydroxylase inhibition, Arch. Int. Pharmacodyn. Ther., 203 (1977) 65--75. 3 Brown, A.W. and Amit, Z., The effects of selective catecholamine depletions by 6-hydroxydopamine on ethanol preference in rats, Neurosci. Lett., 5 (1977) 333--336. 4 Brown, A.W., Amit, Z., Levitan, D.E., Ogren, S-0. and Sutherland, E.A., Noradrenergic mediation of the positive reinforcing properties of enthanol. II. Extinction of ethanol-drinking behavior in laboratory rats by inhibition of dopamine-beta-hydroxylase. Implications for treatment procedures in human alcoholics, Arch. int. Pharmacodyn., 230 (1977) 76--82. 5 Carlsson, A., Engel, J. and Svensson, T., Inhibition of ethanol-induced excitation in mice and rats by alpha-methyl-para-tyrosine, Psychopharmacologia (Berl.) 26 (1972) 307--312. 6 Crow, T.J., Catecholamine-containing neurons and electrical self-stimulation. 1. A review of some data, Psychol. Med., 2 (1972) 414--417. 7 Crow, T.L., Catecholamine-eontaining neurons and electrical self-stimulation. 2. A theoretical interpretation and some psychiatric implications, Psychol. Med., 3 (1973) 1--5. 8 Farley, I.J., Price, K.S., McCullough, E., Deck, J.H.N., Hordynski, W. and Hornykiewicz, O., Norepinephine in chronic paranoid schizophrenia: above-normal levels in lumbic forebrain, Science, 200 (1978) 456--458. 9 Fibiger, H.C., Drugs and reinforcement mechanisms: a critical review of the catecholamine theory, Am. Rev. Pharmacol., 18 (1978) 37--56. 10 Kiianmaa, K., Fuxe, K., Jonsson, G. and Ahtee, L., Evidence for involvement of central NA neurones in alcohol intake. Increased alcohol consumption after degeneration of the NA pathway to the cortex cerebri, Neurosci, Lett., 1 (1975) 41--45. 11 Konig, J.F. and Klippel, R.A., The rat brain, a stereotaxic atlas, Williams and Wilkins Co., Baltimore, 1963. 12 Mason, S.T., Roberts, D.C.S. and Fibiger, H.C., Noradrenaline and neophobia, Physiol. Behav., 21 (1978) 353--361. 13 Mason, S.T., Noradrenaline: Reward or extinction, Neurosci. Biobehav. Rev., in press. 14 McGeer, E.G. and McGeer, P.L., Catecholamine content of spinal cord, Canad. J. Biochem., 40 (1962) 1141--1151. 15 Myers, R.D. and Melchior, C.L., Alcohol drinking in the rat after destruction of serotonergic and catecholaminergic neurons in the brain, Res. Commun. Chem. Path. Pharmacol., 10 (1975) 363--378. 16 Roberts, D.C.S., Zis, A.P. and Fibiger, H.C., Ascending catecholamine pathways and amphetamine induced locomotor activity: importance of dopamine and apparent non-involvement of norepinephrine, Brain Res., 93 (1975) 441--454. 17 Ross, R.A. and Reis, D.J., Effects of lesions of locus coeruleus on regional distribution of dopamine-beta-hydroxylase activity in rat brain, Brain Res., 73 (1974) 161--166. 18 Siegel, A., Nonparametric statistics, McGraw-Hill, 1956. 19 Winer, B.J., Statistical principles in experimental design, McGraw-Hill, 1962.
137
N O R A D R E N A L I N E A N D ETHANOL INTAKE IN THE RAT
S T E P H E N T. M A S O N , M I C H A E L
E. C O R C O R A N *
and H A N S C. FIBIGER
Division of Neurological Sciences, Department of Psychiatry, University of British Columbia, Vancouver V 6 T 1 W 5 (Canada) (Received December 6th, 1978) (Revised version received December 27th, 1978) (Accepted December 27th, 1978)
SUMMARY
Intracerebral injection of 4 pg of the neurotoxin 6-hydroxydopamine (6-OHDA) was used to deplete forebrain noradrenaline (NA) in rats to less than 5% of control values without affecting brain dopamine (DA) and the oral consumption of ethanol examined. Control rats showed a progressive increase in their intake of a 15% ethanol solution and after 15 days were consuming large quantities. This increase did n o t occur in NA depleted rats, which after 15 days had consumed no more than a few miUilitres of the solution in total. The results are discussed in terms of a central noradrenergic basis of ethanol reward.
A number of studies have implicated catecholaminergic mechanisms in the mediation of some of the pharmacological effects of ethanol. Thus, injection of the catecholamine synthesis inhibitor, alpha-methyl-para-tyrosine (AMPT) prevented the usual m o t o r excitation induced by ethanol [ 5], and has been reported to reduce its euphoric effects in humans [ 1 ]. Destruction of catecholaminergic neurones by intraventricular injection of the neurotoxin 6-hydroxydopamine (6-OHDA) has been shown to alter the patterns of oral consumption of ethanol solutions in rats [10,15]. The weakness with previous studies has generally been that no distinction between noradrenaline (NA) and the related catecholamine dopamine (DA) has been made. Thus, AMPT affects the synthesis of both amines and intraventricular 6-OHDA can damage both systems unless additional manipulations are used. Brown and Amit [3] did relate their results to 6-OHDA-induced depletion of NA alone, b u t the anatomical locus of the effect is unclear. Their intraventricular 6-OHDA injections would be expected to result in widespread depletion of NA throughout *Present address: Department of Psychology, University of Victoria, Victoria, B.C. V8W 2Y2 (Canada).
138
the forebrain, cerebellum and spinal cord. We sought to demonstrate a role for the noradrenergic innervation of the forebrain in ethanol consumption by using injections of 6-OHDA into the ascending NA fibre bundle in the mesencephalon that would n o t affect DA systems. 10 male albino Wistar rats (Woodlyn Farms, Ontario) weighing 300 g at the time of operation were anaesthetised with Nembutal (50 mg/kg, intraperitoneal) and positioned in a stereotaxic apparatus. T w o holes were drilled in the skull through which a 34 gauge cannula was lowered bilaterally to the following coordinates: AP ÷ 2.6 mm from interaural line, ML -+ 1.1 mm from midline suture at bregma and DV + 3.7 mm from interaural line [11]. 4 pg of 6-OHDA HBr (Regic Chemicals, weight expressed as free base) dissolved in 2 pl of 0.9% saline with 0.3 mg/ml ascorbic acid antioxidant were infused at the rate of 1 pl/min over 2 min and the cannula was left in place for a further minute to permit diffusion of the drug. The skin was then sutured and 2 weeks were allowed to permit anterograde degeneration of forebrain NA terminals before behavioural testing c o m m e n c e d [ 17 ]. 9 control rats received similar injections of salineascorbate vehicle only. Daily intake of water was measured by the use of the t w o graduated Richter tubes attached to the animal's home cage. After 5 days of water intake a choice was offered between one tube containing 15% ethanol solutions (v/v) and another containing water. These choice days were then alternated with days in which both tubes contained water so as to avoid the effects of dehydration or alteration in fluid balance. Water and ethanol intake was recorded for 15 days of ethanol versus water choice. Following completion of behavioural testing all animals were sacrificed by cervical fracture. Their brains were rapidly removed and dissected on ice as described elsewhere [ 16] into the following regions: hippocampus, cortex, hypothalamus and striatum. These areas were weighed and homogenised in TABLE I POST-MORTEM AMINE ASSAYS V a l u e s are m e a n s + S.E.M. in ng o f amine per g w e t w t . o f tissue. The % c o l u m n is the perc e n t a g e o f c o n t r o l c o n c e n t r a t i o n s remaining in l e s i o n e d tissues.
Controls ( n = 9) NA Hippocampus Cortex Hypothalamus
3 0 5 -+ 18 2 8 9 +- 14 2 3 8 0 -+ 1 1 0
DA Striatum Hypothalamus
1 3 , 6 0 0 -+ 6 6 0 4 5 2 -+ 19
Lesioned ( n = 10)
15 -+ 9 +8 6 0 *-
%
3 6 90
5 3 36
1 2 , 9 0 0 +- 1 2 3 0 421 _+ 26
95 93
139
0.1 N perchloric acid and the endogenous catecholamine c o n t e n t was assayed by the m e t h o d of McGeer and McGeer [14]. This served to confirm that the 6-OHDA injection had produced the expected pattern and extent of amine depletion. The biochemical data shown in Table I indicate that severe and permanent destruction of forebrain noradrenaline neurones occurred. Thus, hippocampal and cortical NA was reduced to less than 5% of control values and marked, but less severe, damage occurred to the hypothalamic innervation, with the NA c o n t e n t being reduced to some 35% of control. No significant alteration in brain dopamine was found with this treatment. The ethanol intake on alternate days of free-choice between 15% (v/v) ethanol solution and water is shown in Fig. 1 for the control and NA-depleted rats. It can be seen that control rats gradually increased their intake over the 15 days so that by the end of this period quite considerable volumes of ethanol solution (mean = 12 ml) were being consumed. The NA-depleted rats, however, failed to increase their intake, and apart from occasional sampling of the ethanol solution, failed to consume more than a few millilitres of it over the entire 15-day period. The total volume of ethanol solution consumed
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o f a 1 5 % ethanol solution (v/v) over 15 days of free-choie between ethanol and water for 10 NA-depleted rats and 9 vehicle injected controls, o D, controls, n = 9 ; m - - - - - - m t r e a t e d , n = 1 0 Fig. 1. Consumption
140
over 15 days is shown in Fig. 2 as a scatter diagram and it can be seen that NA depleted rats tended to drink very little and cluster towards the bottom left-hand comer of the graph, whereas the control rats consumed large volumes (sometimes in excess of 100 ml in toto) and so cluster towards the upper right-hand corner with very little overlap between the two groups. Statistical analysis confirmed the significance of the difference. Thus, the MannWhitney U-test [18] on the total ethanol intake over 15 days revealed a U-value of 10.5,P < 0.01. A two-factor repeated measures analysis of variance [ 19] applied to the daily intake showed that the control and lesioned animals were slgmficantly ditferent (between groups F (1, 17) = 8.53, P < 0.01 and group by days interaction F { 1 4 , 2 3 8 ) = 3.70, P < 0.001). Water intake, both between ethanol days and on the water tube in the
¢r
130
120 110 100
90
80
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30
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.
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18 1I9 R
Fig. 2. Scatter diagram s h o w i n g total c o n s u m p t i o n o f 15% ethanol solution (v/v) over 15 days o f free-choice for 10 N A - d e p l e t e d and 9 vehicle injected rats. ~, controls, n = 9; , , treated, n = 10.
141
ethanol-water choice days, did n o t differ between control and lesioned rats. This is in accord with previous observations [ 1 2 ] . Spontaneous l o c o m o t o r activity of these same animals measured in photocell cages also failed to differ, again consistent with previous reports [ 1 6 ] . The changes in ethanol intake do n o t therefore appear to be secondary to a reduced water-intake or a general lethargy induced by the lesion. The results of this experiment indicate that catecholamines are indeed involved in the voluntary ingestion of ethanol solutions by rats. Depletion of forebraln NA to less than 5% of control values completely prevented the usual, sometimes quite copious, intake of ethanol seen in controls. The experim e n t further indicates that the catecholamine of importance is NA, since loss of brain NA, without any effect on dopamine, was adequate to alter ethanol intake. This thus extends and refines previous work [ 1,3,10,15] suggesting a role of catecholamines in the pharmacological effects of ethanol. The mechanism by which the NA depletion acts to reduce ethanol intake is uncertain. It has been suggested that NA neurones serve a critical role of central reward [6,7] and this has been generalised to include ethanol-reward [2--4]. Since additional work has questioned the involvement of NA in reward generated by food, electrical stimulation of the brain, water, or negative reinforcers such as electric foot-shock or taste aversion paradigms (for review see refs. 9 and 13) it seems less justifiable to invoke a NA system in the reward aspect of ethanol ingestion. A perseveration of responding during withdrawal of reward (in extinction) has been demonstrated after NA depletions (for review see ref. 13) and this inflexibility in altering behaviour might explain the failure of the NA depleted group to increase their ethanol intake in the present experiment. We have preliminary evidence that NA depletion does n o t affect either the 'sensitivity' of the rat to the unpleasant taste of ethanol or the pharmacologically aversive properties of the drug as measured in a taste aversion paradigm, t w o other factors which would be expected to be of importance in determining the amount of ethanol solution consumed voluntarily. Thus, it is n o t immediately clear why NA depletion should reduce the self-administration of ethanol. As a first step in clarifying this, it would be useful to examine the effects of NA depletion on other actions of ethanol and on self-administration in other experimental situations. The clinical relevance of the present study is shown by the use of the noradrenaline synthesis inhibiting drug Antabus ® in the treatment of alcoholism [2--4] and by suggestions of a role for brain NA in other behavioural disorders [ 8 ] .
ACKNOWLEDGEMENTS
The work was supported by the MRC and S.T.M. is in receipt of an MRC Fellowship. The able technical assistance of Betty Richter is gratefully acknowledged.
142 REFERENCES 1 Ahlenius, S., Carlsson, A., Engel, J., Svensson, H. and Sodersten, P., Antagonism by alpha-methyl-para-tyrosine of the ethanol-induced stimulation and euphoria in man, Clin, Pharmacol. Ther., 14 (1973) 586--591. 2 Amit, Z., Brown, W., Levitan, D.E. and Ogren, S.-O., Noradrenergic mediation of the positive reinforcing properties of ethanol. I. Suppression of ethanol in laboratory rats following dopamine-beta-hydroxylase inhibition, Arch. Int. Pharmacodyn. Ther., 203 (1977) 65--75. 3 Brown, A.W. and Amit, Z., The effects of selective catecholamine depletions by 6-hydroxydopamine on ethanol preference in rats, Neurosci. Lett., 5 (1977) 333--336. 4 Brown, A.W., Amit, Z., Levitan, D.E., Ogren, S-0. and Sutherland, E.A., Noradrenergic mediation of the positive reinforcing properties of enthanol. II. Extinction of ethanol-drinking behavior in laboratory rats by inhibition of dopamine-beta-hydroxylase. Implications for treatment procedures in human alcoholics, Arch. int. Pharmacodyn., 230 (1977) 76--82. 5 Carlsson, A., Engel, J. and Svensson, T., Inhibition of ethanol-induced excitation in mice and rats by alpha-methyl-para-tyrosine, Psychopharmacologia (Berl.) 26 (1972) 307--312. 6 Crow, T.J., Catecholamine-containing neurons and electrical self-stimulation. 1. A review of some data, Psychol. Med., 2 (1972) 414--417. 7 Crow, T.L., Catecholamine-eontaining neurons and electrical self-stimulation. 2. A theoretical interpretation and some psychiatric implications, Psychol. Med., 3 (1973) 1--5. 8 Farley, I.J., Price, K.S., McCullough, E., Deck, J.H.N., Hordynski, W. and Hornykiewicz, O., Norepinephine in chronic paranoid schizophrenia: above-normal levels in lumbic forebrain, Science, 200 (1978) 456--458. 9 Fibiger, H.C., Drugs and reinforcement mechanisms: a critical review of the catecholamine theory, Am. Rev. Pharmacol., 18 (1978) 37--56. 10 Kiianmaa, K., Fuxe, K., Jonsson, G. and Ahtee, L., Evidence for involvement of central NA neurones in alcohol intake. Increased alcohol consumption after degeneration of the NA pathway to the cortex cerebri, Neurosci, Lett., 1 (1975) 41--45. 11 Konig, J.F. and Klippel, R.A., The rat brain, a stereotaxic atlas, Williams and Wilkins Co., Baltimore, 1963. 12 Mason, S.T., Roberts, D.C.S. and Fibiger, H.C., Noradrenaline and neophobia, Physiol. Behav., 21 (1978) 353--361. 13 Mason, S.T., Noradrenaline: Reward or extinction, Neurosci. Biobehav. Rev., in press. 14 McGeer, E.G. and McGeer, P.L., Catecholamine content of spinal cord, Canad. J. Biochem., 40 (1962) 1141--1151. 15 Myers, R.D. and Melchior, C.L., Alcohol drinking in the rat after destruction of serotonergic and catecholaminergic neurons in the brain, Res. Commun. Chem. Path. Pharmacol., 10 (1975) 363--378. 16 Roberts, D.C.S., Zis, A.P. and Fibiger, H.C., Ascending catecholamine pathways and amphetamine induced locomotor activity: importance of dopamine and apparent non-involvement of norepinephrine, Brain Res., 93 (1975) 441--454. 17 Ross, R.A. and Reis, D.J., Effects of lesions of locus coeruleus on regional distribution of dopamine-beta-hydroxylase activity in rat brain, Brain Res., 73 (1974) 161--166. 18 Siegel, A., Nonparametric statistics, McGraw-Hill, 1956. 19 Winer, B.J., Statistical principles in experimental design, McGraw-Hill, 1962.