doumalof
Ne.rul ~
J. Neural Transmission 44, 309--316 (1979)
~
n
@ by Springer-Verlag 1979
Distribution
of PNMT
and
Epinephrine
in the
Medulla o b l o n g a t a o f N o r m o t e n s i v e and Spontaneous Hypertensive R a t s * j. Y. Lew, F. Hata, A. Sauter, Y. Baba, J. Engel, and M. Goldstein Department of Psychiatry, Neurochemistry Laboratories, New York University Medical Center, New York, U.S.A. With 1 Figure Received July 27, 1978
Summary The distribution of the Epinephrine forming enzyme (PNMT) activity and Epinephrine (E) levels was investigated in the medulla oblongata of spontaneous hypertensive rats (SH-rats) and in two normotensive strains, namely Wistar Kyoto rats (WK-rats) and Wistar rats. The PNMT activity increases progressively from the caudal to rostral parts in the C1 and C2 regions of the medulla oblongata. The enzyme activity and the E levels are in all parts of the C~ and C2 regions higher in Wistar rats than in WK-rats. The PNMT activity in all parts of the G, region (with the exception of the caudal region), and in the middle part of the C1 region is higher in SH-rats than in WK-rats. The E levels in the SH-rats are higher than in WK-rats in the mediocaudal parts of the C2 and C1 regions.
Introduction Immunohistochemical and biochemical studies have been shown that phenylethanolamine-N-methyltransferase ( P N M T ) and Epinephrine (E) neurons are localized in the C1 and C.~ cell groups of reticular formation in the medulla oblongata and in nerve terminals * Supported by NIMH and NSF grants.
0300-9564/79/0044/0309/8 01.60
310
J.Y. Lew et al.:
in various nuclei of the brain stem and spinal cord [I, 2]. The adrenergic innervation pattern established by immunofluorescence studies suggests that central E may be involved in the regulation of the cardiovascular system. Based on studies of the blockade of the hypotensive and respiratory actions of clonidine by piperoxane, it was postulated by B o l m e et al. [3] that P N M T neurons might be involved in controlling blood pressure. PNMT activity was found to be markedly elevated in the C1 and Ca regions of 4 and 6 week old spontaneous hypertensive rats (SHrats) [4, 5] and in the C1 region of adult DOCA salt hypertensive rats [4]. E levels were reported to be elevated in the C2 regions but not in the C1 regions of SH-rats when compared with Wistar Kyoto (WK) rats [6]. Since there is a significant genetic variation in the levels of catecholamine (CA) biosynthetic enzymes in various inbred rat strains [7] we have determined the distribution of PNMT activity and E levels in the medulla oblongata of SH-rats and in two normotensive strains namely in WK-rats and in Wistar rats. Methods Male rats of inbred Wistar strain, spontaneous hypertensive rats (SHrats), and Wistar Kyoto rats (WK-rats) ('Taconic Farms, Germantown, N.Y.) were used in this study. All animals were maintained under identical conditions for at least one week. Blood pressure measurements were carried out with a tail-sphygmographic method. The animals were killed by decapitation and the brains were taken out rapidly and frozen on dry ice. Serial sections, of 500 F~m were cut in a cryostat at --10 ~ from the level of the nucleus nervi facialis to the pyramidal decussation. Five slices were made, the most caudal slice was designated, "a" and the most rostral, "e" (Fig. 1). The selected regions were then punched out (1.0 mm diameter) under the dissecting microscope. The PNMT activity was assayed by a previously described procedure [8], using DL-phenylethanolamine as the methyl-accepting substrate and HZ-methyl-S-adenosyl-L-methionine as the methyl donating substrate [9]. Epinephrine was assayed by a radioenzymatic procedure [ 10]. Results The results presented in Table 1 show that PNMT activity increases progressively from the caudal to rostral parts in the C1 and C.~ regions of the medulla oblongata. The PNMT activity in all parts of the C1 and Ca regions is higher in the Wistar rats than in the WKrats or SH-rats. In the Ca region the PNMT activity of SH-rats is
Distribution of PNMT and Epinephrine in the Medulla oblongata
0
0
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G'-, ,::,o G", x D
0
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311
312
J.Y. Lew et al.:
significantly higher than in the WK-rats in all analyzed parts with the exception of the caudal part (section a, Fig. 1). In the C1 region the P N M T activity of the SH-rats is higher than in the WK-rats only in the middle part (section c, Fig. 1) but not in the other analyzed parts. The results presented in Table 2 show the E levels in the caudalrostral parts of the C1 and C2 regions in the three strains of rats. The E levels are in all parts of the C1 and Ce regions of the medulla oblongata significantly higher in the Wistar rats than in the WK-rats or SH-rats. The E levels are significantly higher in the SH-rats than in
I.--- P.'. i Y L b
a
2
Fig. 1. Schematic illustration of the dissected areas. P S.O mm (a) is the most caudal level and P 4.5 mm (f) is the most rostral level. Abbreviations were the same as
previously described [14]. The following regions were punched out: C 1 Region: (section a--d) N. reticularis lateralis and adjacent structures (A.S.); (section e) N. originis nervi facialis, and A.S. Co. Region: (section a) N. tractus solitarii, N. commisuralis, and A.S.; (section b) N. tractus solitarii, N. intercalatus, and A.S.; (section c) N. tractus solitarii, N. originis dorsalis vagi, N. originis nervi hypoglossi, and A.S.; (section d) N. tractus solitarii, N. originis nervi hypoglossi, and A.S.; (section e) N. tractus solitarii, N. vestibularis medialis, N. prep0situs hypoglossi,and A.S.
Distribution of P N M T and Epinephrine in the Medulla oblongata
~
O
+1 +1 +1 +I +1
~q~qq ~
O
~
+l+l+l+l+l ~
0
~
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~
m
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l
+1 +1+1 + l + l 0 0 0 0 ~
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~
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o
21 Journal of Nem'al Transmission 44/4
313
314
J.Y. Lew et al.:
the WK-rats only in the mediocaudal parts of the C~ region (section a and b, Fig. 1) and C~ region (section b, Fig. 1). The P N M T activity and E levels in the area postrema of SH-rats were significantly higher than in the WK-rats. However, the dissected area postrema (section b, Fig. 1) probably contains some medial aspects of the nucleus tractus solitarii complex. Thus P N M T and E may not necessarily be localized in the area postrema. At the age of six weeks the systolic blood pressure of SH-rats was 140_+5 (n = 18), of WK-rats 115+5 (n = 18), and of Wistar rats 110 _+ 3 mm Hg (n = 10).
Discussion
The results of this study show that P N M T activity in the C1 and C2 regions of the medulla oblongata increases progressively from the caudal to rostral planes while the E levels are the highest in the medial parts. The distribution of P N M T activity is compatible with the immunofluorescence results [1, 2] which show that the density of P N M T containing cell bodies is higher in the C1 and C2 rostral regions while the density of the P N M T containing dendrites and terminals is higher in the mediocaudal regions. The heterogenous distribution of P N M T activity and of E in the C1 and C2 regions of the medulla oblongata could perhaps explain some of the reported differences in the levels of P N M T and E in these regions. In this study we have found that E levels are higher in the SH-rats than in the WK-rats only in the mediocaudal parts of the C2 and C1 regions. Wijnen et al. [11] have reported that E levels are elevated in the C2 regions of SH-rats when compared to WK-rats, while Saavedra [12] have recently found that the E levels are not elevated in the C~ region of SH-rats. It is conceivable that in these two studies the E levels were determined in different rostro-caudal parts of the C2 region and therefore different results were obtained. The immunohistochemical data has revealed that P N M T containing neurons are located in the C2 region of the medulla oblongata which contains the nucleus tractus solitarii, an area which is implicated in the control of blood pressure. The previously reported biochemical results that P N M T activity [4] and E levels [6, 11] in the C~ region are higher in the SH-rats than in the WK-rats further supports the idea that adrenergic neurons are involved in the regulation of blood pressure. However, the observed increase in the P N M T activity and E levels in the C~ and C1 regions of SH-rats could be due to a genetic influence occurring specifically in this particular group of cell bodies
Distribution of PNMT and Epinephrine in the Medulla oblongata
315
which may not necessarily be related to the development of hypertension. In the present study we have therefore investigated the distribution of P N M T activity and E levels in one hypertensive strain and two normotensive strains of rats. It is apparent from our data that there is a significant genetic variation in the brain P N M T activity and E levels. One is tempted to postulate that at least two components influence P N M T and E levels in the C1 and C2 regions of the medulla oblongata. One component not related to the development of hypertension and another perhaps related to the development of hypertension. The component which is not related to the development of hypertension appears to have a more pronounced influence on brain P N M T and E levels. To elucidate the role of the E neurons in the development of hypertension the effects of P N M T inhibitors on blood pressure were investigated. The systemic administration of the P N M T inhibitor SKF 7698 [4] or of SKF 64139 [13] results in a lowering of blood pressure. It is noteworthy that the intraventricular or intracerebral administration of SKF 64139 results in a marked elevation of blood pressure. In conscious rats prepared for intra-arterial recording of blood pressure bilateral administration of 100/~g SKF 64139 into the medial parts of the C2 region results in a marked elevation of blood pressure for a period of 30--45 rain. However, intracerebral administration of a structural analog of SKF 64139, namely 72223 which is not a P N M T inhibitor (Pendleton, private communication) also elevates the blood pressure. These findings raise some doubts whether the elevation of blood pressure by SKF 64139 is related to its inhibition of the E forming enzyme. It should be pointed out that SKF 64139 and SKF 72223 have some structural resemblance with papevarine, which is also an isoquinoline derivative. Since papevarine is a known vasodilator it is possible that following systemic administration of the SKF compounds the blood pressure is decreased due to vasodilation. Thus, the elucidation of the role of central E in controlling blood pressure must await the development of more specific P N M T inhibitors. References
[1] H6kfelt, T., Fuxe, K., Goldstein, M., ]ohansson, 0.: Evidence for adrenaline neurons in the rat brain. Acta Physiol. Scand. 89, 286--288 (1973). [2] H~Skfelt, T., Fuxe, K., Goldstein, M., Johansson, 0.: Immunohistochemical evidence for the existence of adrenaline neurons in the rat brain. Brain Research 66, 235--251 (1974). 21"
316
J.Y. Lew et al.: PNMT and Epinephrine in the Medulla oblongata
[3] Bolrne, H., Corrodi, H., Fuxe, K., H6kfelt, T., Lidbrink, P., Goldstein, M.: Possible involvement of central adrenaline neurons in vasomotor and respiratory control. Studies with clonidine and its interactions with piperoxane and yohimbine. European J. Pharmacol. 28, 89--94 (1974). [4] Saavedra, J.M., Grobecker, H., Axelrod, J.: Adrenaline-forming enzyme in brainstem: Elevation in genetic and experimental hypertension. Science 191,483--484 (1976). [5] Saavedra, ]. M., Grobecker, H., Axelrod, J.: Changes in central catecholaminergic neurons in the spontaneously (genetic) hypertensive rat. Circulation Research 42 (1978). [6] Versteeg, D. H.G., Palkovits, M., Van Der Gugten, J., Wijnen, L.J.M., Srneets, G. W. M., DeJong, W.: Catecholamine content of individual brain regions of spontaneously hypertensive rats (SH-rats). Brain Research 112, 429--434 (1976). [7] Nagaoka, A., Lovenberg, W.: Regional changes in the activities of aminergic biosynthetic enzymes in the brains of hypertensive rats. European J. Pharmacol. 43, 297--306 (1977). [8] Deguchi, T., Barchas, J. D.: Inhibition of transmethylation of biogenic amines by S-adenosylhcmocysteine. J. Biol. Chem. 246, 3175--3181 (1971). [9] Saavedra, J.M., Palkovits, M., Brownstein, M.J., Axelrod, J.: Localization of phenylethanolamine-N-methyltransferase in the brain nuclei. Nature (Lond.) 248, 695 (1974). [10] DaPrada, M., Zuricher, G.: Simultaneous enzymatic determination of plasma and tissue adrenaline, noradrenaline and dopamine within the fentomole range. Life Sci. 16, 1161--1174 (1976). [11] Wijnen, H. J. L. M., Versteeg, D. H. G., Palkovits, M., DeJong, W.: Increased adrenaline content of individual nuclei of the hypothalamus and the medulla oblongata of genetically hypertensive rats. Brain Research 135, 180--185 (1977). [12] Saavedra, J. M.: Unpublished data. [13] Sauter, A. M., Lew, J. Y., Baba, Y., Goldstein, M.: Effect of phenylethanolamine-N-methyltransferase and dopamine-fl-hydroxylase inhibition on epinephrine levels in the brain. Life Sci. 21, 261--266 (1977). [14] Goldstein, M., Lew, J.Y., Matsumoto, Y., H6kfelt, T., Fuxe, K.: Localization and function of PNMT in the central nervous system. In: Psychopharmacology: A Generation of Progress (Lipton, M.A., DiMascio, A., Killarn, K. F., eds.). New York: Raven Press. 1978. Authors' address: Dr. J. Y. Lew, Department of Psychiatry, Neurochemistry Laboratories, New York University Medical Center, 550 First Avenue, New York, NY 10016, U.S.A.
Ne.rul ~
J. Neural Transmission 44, 309--316 (1979)
~
n
@ by Springer-Verlag 1979
Distribution
of PNMT
and
Epinephrine
in the
Medulla o b l o n g a t a o f N o r m o t e n s i v e and Spontaneous Hypertensive R a t s * j. Y. Lew, F. Hata, A. Sauter, Y. Baba, J. Engel, and M. Goldstein Department of Psychiatry, Neurochemistry Laboratories, New York University Medical Center, New York, U.S.A. With 1 Figure Received July 27, 1978
Summary The distribution of the Epinephrine forming enzyme (PNMT) activity and Epinephrine (E) levels was investigated in the medulla oblongata of spontaneous hypertensive rats (SH-rats) and in two normotensive strains, namely Wistar Kyoto rats (WK-rats) and Wistar rats. The PNMT activity increases progressively from the caudal to rostral parts in the C1 and C2 regions of the medulla oblongata. The enzyme activity and the E levels are in all parts of the C~ and C2 regions higher in Wistar rats than in WK-rats. The PNMT activity in all parts of the G, region (with the exception of the caudal region), and in the middle part of the C1 region is higher in SH-rats than in WK-rats. The E levels in the SH-rats are higher than in WK-rats in the mediocaudal parts of the C2 and C1 regions.
Introduction Immunohistochemical and biochemical studies have been shown that phenylethanolamine-N-methyltransferase ( P N M T ) and Epinephrine (E) neurons are localized in the C1 and C.~ cell groups of reticular formation in the medulla oblongata and in nerve terminals * Supported by NIMH and NSF grants.
0300-9564/79/0044/0309/8 01.60
310
J.Y. Lew et al.:
in various nuclei of the brain stem and spinal cord [I, 2]. The adrenergic innervation pattern established by immunofluorescence studies suggests that central E may be involved in the regulation of the cardiovascular system. Based on studies of the blockade of the hypotensive and respiratory actions of clonidine by piperoxane, it was postulated by B o l m e et al. [3] that P N M T neurons might be involved in controlling blood pressure. PNMT activity was found to be markedly elevated in the C1 and Ca regions of 4 and 6 week old spontaneous hypertensive rats (SHrats) [4, 5] and in the C1 region of adult DOCA salt hypertensive rats [4]. E levels were reported to be elevated in the C2 regions but not in the C1 regions of SH-rats when compared with Wistar Kyoto (WK) rats [6]. Since there is a significant genetic variation in the levels of catecholamine (CA) biosynthetic enzymes in various inbred rat strains [7] we have determined the distribution of PNMT activity and E levels in the medulla oblongata of SH-rats and in two normotensive strains namely in WK-rats and in Wistar rats. Methods Male rats of inbred Wistar strain, spontaneous hypertensive rats (SHrats), and Wistar Kyoto rats (WK-rats) ('Taconic Farms, Germantown, N.Y.) were used in this study. All animals were maintained under identical conditions for at least one week. Blood pressure measurements were carried out with a tail-sphygmographic method. The animals were killed by decapitation and the brains were taken out rapidly and frozen on dry ice. Serial sections, of 500 F~m were cut in a cryostat at --10 ~ from the level of the nucleus nervi facialis to the pyramidal decussation. Five slices were made, the most caudal slice was designated, "a" and the most rostral, "e" (Fig. 1). The selected regions were then punched out (1.0 mm diameter) under the dissecting microscope. The PNMT activity was assayed by a previously described procedure [8], using DL-phenylethanolamine as the methyl-accepting substrate and HZ-methyl-S-adenosyl-L-methionine as the methyl donating substrate [9]. Epinephrine was assayed by a radioenzymatic procedure [ 10]. Results The results presented in Table 1 show that PNMT activity increases progressively from the caudal to rostral parts in the C1 and C.~ regions of the medulla oblongata. The PNMT activity in all parts of the C1 and Ca regions is higher in the Wistar rats than in the WKrats or SH-rats. In the Ca region the PNMT activity of SH-rats is
Distribution of PNMT and Epinephrine in the Medulla oblongata
0
0
.,-, ~0 0
-H 4-1 +1 4-1 +l 9, , ~
G'-, ,::,o G", x D
0
0
u~
t
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,b
311
312
J.Y. Lew et al.:
significantly higher than in the WK-rats in all analyzed parts with the exception of the caudal part (section a, Fig. 1). In the C1 region the P N M T activity of the SH-rats is higher than in the WK-rats only in the middle part (section c, Fig. 1) but not in the other analyzed parts. The results presented in Table 2 show the E levels in the caudalrostral parts of the C1 and C2 regions in the three strains of rats. The E levels are in all parts of the C1 and Ce regions of the medulla oblongata significantly higher in the Wistar rats than in the WK-rats or SH-rats. The E levels are significantly higher in the SH-rats than in
I.--- P.'. i Y L b
a
2
Fig. 1. Schematic illustration of the dissected areas. P S.O mm (a) is the most caudal level and P 4.5 mm (f) is the most rostral level. Abbreviations were the same as
previously described [14]. The following regions were punched out: C 1 Region: (section a--d) N. reticularis lateralis and adjacent structures (A.S.); (section e) N. originis nervi facialis, and A.S. Co. Region: (section a) N. tractus solitarii, N. commisuralis, and A.S.; (section b) N. tractus solitarii, N. intercalatus, and A.S.; (section c) N. tractus solitarii, N. originis dorsalis vagi, N. originis nervi hypoglossi, and A.S.; (section d) N. tractus solitarii, N. originis nervi hypoglossi, and A.S.; (section e) N. tractus solitarii, N. vestibularis medialis, N. prep0situs hypoglossi,and A.S.
Distribution of P N M T and Epinephrine in the Medulla oblongata
~
O
+1 +1 +1 +I +1
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~
+l+l+l+l+l ~
0
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21 Journal of Nem'al Transmission 44/4
313
314
J.Y. Lew et al.:
the WK-rats only in the mediocaudal parts of the C~ region (section a and b, Fig. 1) and C~ region (section b, Fig. 1). The P N M T activity and E levels in the area postrema of SH-rats were significantly higher than in the WK-rats. However, the dissected area postrema (section b, Fig. 1) probably contains some medial aspects of the nucleus tractus solitarii complex. Thus P N M T and E may not necessarily be localized in the area postrema. At the age of six weeks the systolic blood pressure of SH-rats was 140_+5 (n = 18), of WK-rats 115+5 (n = 18), and of Wistar rats 110 _+ 3 mm Hg (n = 10).
Discussion
The results of this study show that P N M T activity in the C1 and C2 regions of the medulla oblongata increases progressively from the caudal to rostral planes while the E levels are the highest in the medial parts. The distribution of P N M T activity is compatible with the immunofluorescence results [1, 2] which show that the density of P N M T containing cell bodies is higher in the C1 and C2 rostral regions while the density of the P N M T containing dendrites and terminals is higher in the mediocaudal regions. The heterogenous distribution of P N M T activity and of E in the C1 and C2 regions of the medulla oblongata could perhaps explain some of the reported differences in the levels of P N M T and E in these regions. In this study we have found that E levels are higher in the SH-rats than in the WK-rats only in the mediocaudal parts of the C2 and C1 regions. Wijnen et al. [11] have reported that E levels are elevated in the C2 regions of SH-rats when compared to WK-rats, while Saavedra [12] have recently found that the E levels are not elevated in the C~ region of SH-rats. It is conceivable that in these two studies the E levels were determined in different rostro-caudal parts of the C2 region and therefore different results were obtained. The immunohistochemical data has revealed that P N M T containing neurons are located in the C2 region of the medulla oblongata which contains the nucleus tractus solitarii, an area which is implicated in the control of blood pressure. The previously reported biochemical results that P N M T activity [4] and E levels [6, 11] in the C~ region are higher in the SH-rats than in the WK-rats further supports the idea that adrenergic neurons are involved in the regulation of blood pressure. However, the observed increase in the P N M T activity and E levels in the C~ and C1 regions of SH-rats could be due to a genetic influence occurring specifically in this particular group of cell bodies
Distribution of PNMT and Epinephrine in the Medulla oblongata
315
which may not necessarily be related to the development of hypertension. In the present study we have therefore investigated the distribution of P N M T activity and E levels in one hypertensive strain and two normotensive strains of rats. It is apparent from our data that there is a significant genetic variation in the brain P N M T activity and E levels. One is tempted to postulate that at least two components influence P N M T and E levels in the C1 and C2 regions of the medulla oblongata. One component not related to the development of hypertension and another perhaps related to the development of hypertension. The component which is not related to the development of hypertension appears to have a more pronounced influence on brain P N M T and E levels. To elucidate the role of the E neurons in the development of hypertension the effects of P N M T inhibitors on blood pressure were investigated. The systemic administration of the P N M T inhibitor SKF 7698 [4] or of SKF 64139 [13] results in a lowering of blood pressure. It is noteworthy that the intraventricular or intracerebral administration of SKF 64139 results in a marked elevation of blood pressure. In conscious rats prepared for intra-arterial recording of blood pressure bilateral administration of 100/~g SKF 64139 into the medial parts of the C2 region results in a marked elevation of blood pressure for a period of 30--45 rain. However, intracerebral administration of a structural analog of SKF 64139, namely 72223 which is not a P N M T inhibitor (Pendleton, private communication) also elevates the blood pressure. These findings raise some doubts whether the elevation of blood pressure by SKF 64139 is related to its inhibition of the E forming enzyme. It should be pointed out that SKF 64139 and SKF 72223 have some structural resemblance with papevarine, which is also an isoquinoline derivative. Since papevarine is a known vasodilator it is possible that following systemic administration of the SKF compounds the blood pressure is decreased due to vasodilation. Thus, the elucidation of the role of central E in controlling blood pressure must await the development of more specific P N M T inhibitors. References
[1] H6kfelt, T., Fuxe, K., Goldstein, M., ]ohansson, 0.: Evidence for adrenaline neurons in the rat brain. Acta Physiol. Scand. 89, 286--288 (1973). [2] H~Skfelt, T., Fuxe, K., Goldstein, M., Johansson, 0.: Immunohistochemical evidence for the existence of adrenaline neurons in the rat brain. Brain Research 66, 235--251 (1974). 21"
316
J.Y. Lew et al.: PNMT and Epinephrine in the Medulla oblongata
[3] Bolrne, H., Corrodi, H., Fuxe, K., H6kfelt, T., Lidbrink, P., Goldstein, M.: Possible involvement of central adrenaline neurons in vasomotor and respiratory control. Studies with clonidine and its interactions with piperoxane and yohimbine. European J. Pharmacol. 28, 89--94 (1974). [4] Saavedra, J.M., Grobecker, H., Axelrod, J.: Adrenaline-forming enzyme in brainstem: Elevation in genetic and experimental hypertension. Science 191,483--484 (1976). [5] Saavedra, ]. M., Grobecker, H., Axelrod, J.: Changes in central catecholaminergic neurons in the spontaneously (genetic) hypertensive rat. Circulation Research 42 (1978). [6] Versteeg, D. H.G., Palkovits, M., Van Der Gugten, J., Wijnen, L.J.M., Srneets, G. W. M., DeJong, W.: Catecholamine content of individual brain regions of spontaneously hypertensive rats (SH-rats). Brain Research 112, 429--434 (1976). [7] Nagaoka, A., Lovenberg, W.: Regional changes in the activities of aminergic biosynthetic enzymes in the brains of hypertensive rats. European J. Pharmacol. 43, 297--306 (1977). [8] Deguchi, T., Barchas, J. D.: Inhibition of transmethylation of biogenic amines by S-adenosylhcmocysteine. J. Biol. Chem. 246, 3175--3181 (1971). [9] Saavedra, J.M., Palkovits, M., Brownstein, M.J., Axelrod, J.: Localization of phenylethanolamine-N-methyltransferase in the brain nuclei. Nature (Lond.) 248, 695 (1974). [10] DaPrada, M., Zuricher, G.: Simultaneous enzymatic determination of plasma and tissue adrenaline, noradrenaline and dopamine within the fentomole range. Life Sci. 16, 1161--1174 (1976). [11] Wijnen, H. J. L. M., Versteeg, D. H. G., Palkovits, M., DeJong, W.: Increased adrenaline content of individual nuclei of the hypothalamus and the medulla oblongata of genetically hypertensive rats. Brain Research 135, 180--185 (1977). [12] Saavedra, J. M.: Unpublished data. [13] Sauter, A. M., Lew, J. Y., Baba, Y., Goldstein, M.: Effect of phenylethanolamine-N-methyltransferase and dopamine-fl-hydroxylase inhibition on epinephrine levels in the brain. Life Sci. 21, 261--266 (1977). [14] Goldstein, M., Lew, J.Y., Matsumoto, Y., H6kfelt, T., Fuxe, K.: Localization and function of PNMT in the central nervous system. In: Psychopharmacology: A Generation of Progress (Lipton, M.A., DiMascio, A., Killarn, K. F., eds.). New York: Raven Press. 1978. Authors' address: Dr. J. Y. Lew, Department of Psychiatry, Neurochemistry Laboratories, New York University Medical Center, 550 First Avenue, New York, NY 10016, U.S.A.
