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Changes in biogenic amines in rat hippocampus during development and aging
Life Sciences, Vol. 42, pp. 2503-2508 Printed in the U.S.A.
Pergamon Press
CHANGESIN BICGENIC AMINES IN RAT HIPPKAhWS M. Santiagoa,
DURING DEVELOPMZNTAND AGING
A. Machadoa, F. Reinoso-Suirezb
and J. Canoa’Y
aDepartamento de Bioquimica. Facultad de Farrrncia. 41012-SEVILLA and bDepartamento de Morfologia. Facultad de Medicina. Universidad Aut6norra de h4drid. Spain. (Received
in final
form April
14, 1988)
SUMVWRY The effects of postnatal development and aging on the of dopamine, noradrenal ine, serotonin and their concentration principle metabolites have been studied in the hippocanpus of the rat. During development the concentration of dopamine increases 1.5 fold during the first 90 days. 3-methoxytyramine \nas found in low concentrations. The homovanillic acid and DOPAC concentrations showed no changes apart from a decrease at day 15 and an increase at day 8, respectively. Fran birth up to 30 months, the noradrenaline concentration increased by a factor of about 10. Their metabolites each showed a different profile. The concentration of tryptophan \k~s almys the highest amcng the conpounds studied. It decreased f ran birth to day 15, while the concentration of serotonin and 5_hydroxyindolacetic acid increased 3 and 5 fold respectively during this time. However, 5_hydroxyt ryptophan and 5-hydroxyttyptophol concentrations were very low and unchanged at all stages. These findings led to the conclusion that the neurotransmitters: noradrenaline and serotonin, are developed in the hippocanpus during the first three months. During aging, the serotonin concentration is increased without significant change in the other conpounds studied. The hippocanpus (HP) plays an irrportant role in short term memory (1) and locomotor activity (2). The memory changes or losses during a life time are due to the nom1 aging process (3) and occur even more rapidly when senile dementia occurs (4). It is kn0v.n that axons containing dopamine (DA), noradrenal ine (NA) , serotonin 6HT), as well as other neurotransmitters, converge in the HP (5-9). Sune research has been carried out in order to clarify the role of hippocarrpal NA and 5-HT. The underlying assumption is that the HP rrny be the integrating structure for the expressian of NA and S-HT effects an behaviour (10). It has been suggested that the brain NA is involved in some motor activity mechanisms such as: theta rhythm generation and modulation of the hippocanpal in response to behaviourally significant stirmli, coding for non-rekard, learning and memory (11-13). At the same time, several reports have questioned tiether the locus coeruleus system is involved in attention, learning or memory (14,151. In most of these phenomena NA plays a facilitatory role.
*
To Tom all
correspondence
shmld
be addressed.
0024-3205/88 $3.00 + .OO Copyright (c) 1988 Pergamon Press
plc
2504
Biogenic
Amines in Bat Hippocampus
Vol.
42, No. 24, 1988
I&h less is larom about the role of the hippocanpal serotaninergic system. There is evidence that serotonin has an inhibitory ef feet on the activity of the hippocaspal neurons, motor activity, learning and memory and pain perception (2,161. Pathological changes in the raphe system may al so inpair memory (17). The HP is a brain region with a relatively small dopaminergic innervation. The dopaminergic activity is layoff to be involved in the septo hippocanpal path-y (18,191. The aim of this work v.ns to study the behaviour of DA, NA and 5-HT and the concentrations of their main metabolites (3_methoxytyramine, 3-MT; 3,4-dihydroxyphenylacetic acid, DOPAC; hanovanillic acid, HVA; 3-methoxy-4- hydroxyphenylglycol , M-K; normetanephrine, NM; metanephrine, MJ; tryptophan, ttyp; 5-hydroxyttyptophan, 5-HTP; 5-hydraxyindolacetic acid, 5-HIAA; and 5-hydroxy5-HTOL) during the developmental and aging periods in the HP of t ryptophol, the rat, in order to understand changes and look for some correlation between behavicur changes described during this period.
The performed
measurement of the biogenic according to methods described
amines and their elsewhere (20).
metabolites
was
Cur study was performed on male rats of the Wi star strain. These were maintained on a 12-h dark/l2-h light cycle and allowed free access to food and wnter. The anirrals at all stages were decapitated between 10.00 and 11.00 a.m. and the whole brain \nas quickly removed and dissected at OK using a A cut was made thrash the corpus callosum and the dissecting microscope. cortex ms peeled back exposing the HP which MIS carefully removed. Statistical analyses: behavioural data were treated variance (Snedecor’s F-test). Observed mean differences Tuckey’s t-test.
via analysis of the were evaluated with
RESULTS Table I shows the content of DA and its metabolites. The DA underwent a increase between days 0 and 90, but withat any statistically slight significant differences during any of the stages studied. The adult level (3 months) found was in relatively good agreement with those obtained by other authors (21,221. During development and aging, 3-MT had the lowest concentration of any DA metabolites studied (ranging between 4.1 and 10.9 nglg wet tissue) and was not detectable at birth. DOPAC and HVA developmental profiles were different during the first stages of development. COPAC underwent a significant increase fran day 0 to day 8 (287.fX, PcO.05, Tuckey’s t-test), HVA underwent a decrease at day 15 (41.4%). However, among while in contrast, DA metabolites only the DOPAC showed a statistical change. The amount of NA and its metabolites found in the HP is presented in table II. This catecholamine underwent an increase during postnatal development up to 3 nxxtths. When the first stages (0, 8, 15 and 30 days) are curpared with the others (1, 3, 6, 12, 24 and 30 months) they show statistically significant changes (table II). There were no statistical differences after 3 The NA concentration found in the adult rat (3 nuxlths.1 conpares mxlths. favorably with that reported by other investigators (21-24).
Biogenic
Vol. 42, No. 24, 1988
2505
Amines in Rat Hippocampus
TABLE I Concentration
of Dopamine and its Age in days 8 15
0
Metabolites
in the Rat Hippocanpus.
3
30
6
Age in months 24 12
30
DA
16.0 *1.2 (6,
17.4 +1.1 (6)
18.7 22.1 (10)
21.0 il.2 (7)
24.3 k3.5 (4)
19.5 *1.0 (5)
19.8 kO.4 (4)
20.3 +1.8 (4)
20.6 k3.6 (4)
3-W
n.d.
7.9 +0.7 (4)
8.3 *0.7 (4)
8.0 +0.6 (6,
10.9 kO.6 (4)
10.3 fl.1 (4)
7.1 kO.3 (4)
8.8 *0.8 (4)
4.1 +o.g (4)
DOPAC
5.4 *o. 7l (4)
20.9 20.6 (61~
19.2 *1.1 (lOI3
20.6 +1.3 (514
13.8 k1.6 (4)
15.5 k0.6 (5)
9.6 f0. 75 (4)
10.7 *1.26 (4)
12.9 *0.7 (4)
HVA
27.9 Zt1.1 (6,
27.5 f1.4 (4)
16.1 +1.6 (4)
14.5 kO.8 (5)
16.7 k2.8 (4)
21.5 +2.0 (6)
15.6 *3.5 (4)
16.3 *1.9 (4)
17.6 *1.3 (4)
Results are given in rig/g wet tissue as mean + SEM for the nurrber of animals in parentheses. n.d.= not detectable. Behavioural data were analyzed by ANOVA. (Tuckey’s t-test): 2-4 vs . 1,536., P
of Noradrenaline Age in days 15 8
32.8 *2.S1 (6,
59.0 i2.72 (5)
74.5 *2.S3 (12)
n.d.
19.3
21.4
n.d.
n.d.
and its
30
3
163.9 +9.g4 (7)
316.8 k12.5 (415
29.3
Metabolites b
in the Rat Hippocanpus.
Age in months 12 24
30
283.5 *11.76 (6,
290.8 *6. g7 (4)
306.6 *lo. 3 (4?
324.5 *13.0g (4)
53.8
56.8
64.3
45.9
47.4
‘;;‘;12
*;;;13
*;;;14
4.4 *0.6 (4,18
8.0
19.4
27.8
24.4
27.6
30.0
20.8
‘&‘;19
*:;;20
‘$$21
*;;;22
+:4;23
+;4;24
*;$25
n.d.
n.d.
n.d.
3.1 *0.4 (4)
6.4 kO.6 (4)
8.9 1tO.6 (4)
8.1 20.9 (4)
7.6 Al.0 (4)
Results are given in rig/g wet tissue in parentheses. n.d.= not detectable.
as mean f SEM for the nutiber of animals Behavicural data were analyzed by MVA. 4,8,9 10,ll Statistical significance (Tuckey’s t-test): 4 vs. l-3; 5 vs vs. 13-17; 12 vs 16,17, 18 vs 21-25, 19 vs 23,24,) P
None of NA metabolites studied were detectable at birth. M-KG WIS found to have the highest concentration, and at day 8 and 15 showed statistical changes hen ccrrpared with day 90 cnv,ards. NM showed a behaviour similar to MPG. W was not f-d in detectable levels up to 3 months, and the level rained very low during aging (ranging between 3.1 and 8.9 nglg wet tissue).
Biogenic
2506
Amines
in
Rat Hippocampus
Vol.
42,
No.
24,
1980
As can be seen from table III, the concentration of tryptophan was found It underwent a decrease during development up to day 15 to be the highest. (65.696, PcO.05, as coqared with day 0). From day 15 onwards no statistical differences were found. The 5-HTP was not detectable up to 3 months and, after its concentration was very low during all stages studied (ranging that, between 3.6 and 6.0 nglg wet tissue). The 5-HT continued to increase throughout (table III). With respect to 5_HIAA, the nain 5-HT metabolite, the three first stages (0, 8 and 15 days) showed some statistical changes as conpared with other stages. Thereafter, it renained without statistically significant changes, apart fom differences observed when conparing levels at 30 days with those at 24 (45.896, P
TABLE II1 Concentration
Age 8
0 Trvu aL 5-HTP
8615.4 k379.4 (6+ n.d.
5-HT
78.5 ‘$0
5-HIAA
5-HTOL
of
2963.8 k100.1 (413
its
Metabolites
2930.0 k132.7 (414
n.d.
n.d.
138.5
181.8
238.6
:70;12
*&;13
202.6
3 3100.4 ?69.25 (4)
2454.1 ?126.B6 (5)
6.0 +o.g (4)
4.7 kO.5 (4)
264.5
259.1
*:;;14
+;6;20
$~21
?$;22
10.1 +1.1 (4)
10.4 +-0.9 (4)
7.8 kO.7 (4)
8.9 kO.5 (8)
10.1 fl.1 (4)
22
253.1
nglg wet tissue not detectable.
,
l
vs. 26,27;
2284.5 ?127.67 (41
2528.6 *47.g8 (4)
3.6 +0.3 (4)
5.7 kO.7 (4)
21 v,.
30 2425.1 +67. 3g (4) 6.0 fl.1 (4) 358.1
346.7 512.5 +22. B16 - f4) ‘T&7
“:;:18 379.5
319.8
+2:4:24
+2;$25
+$;26
+~$27
8.3 +0.6 (4)
10.0 kO.5 (4)
9.1 fl.1 (4)
7.4 +1.2 (4)
as means * SEM for
4,&g;
Hippocanpus.
285.2
Behavioural 1 (Tuckey’s t-test )* 13,15 vs 16,18. 17 vs
26127: p
Rat
in months 12 24
*;;;15
*:&-;19
significance 11 13-15; vs.
the
6
318.1 +34.6 - f4,23
113.5
in Age
30
n.d.
*;6;11
58.6
Statistical 12,14,15; 10_13;15;
and
in days 15
5155.4 k442.2 (61~
Results are given in in parentheses. n.d.=
23-26:
Serotonin
data
10’ 27;
P
369.0
the number of anirral s
were
analyzed
by ANoVA.
Vol.
42, No. 24, 1988
Biogenic
Amines in Bat Hippocampus
2507
DISCUSSION The HP has been identified as critical for the mediation of normal memory. It has been reported that dopaminergic neurons could have a modulatory (26). As our results show DA, as well as its influence on memory processes DOPAC, HVA and 3-MI’ are not markedly modified, thagh I-WA levels metabolites, It is to be noted that at birth the DA content WLS very decrease slightly. was similar to that of the adult. This seems to suggest that the DA path-y more developed at birth than those of the NA and 5-HT. Though, at present it is not safe to conclude that a change in any of the metabolites reflects a it roust be kept in mind that 3-MI levels are variation in DA neuron activity, cannonly considered as a reliable indicator of DA release (27). Therefore, our results point tmrds the lack of changes in hippocarrpal dopaminergic activity and release during development and aging. were the highest found. They underwent a concentrations Tryptophan statistical decrease throughout the developmental period, nrtinly during the first fifteen days. The changes in tryptophan in the brain could be related to the tryptophan concentration in the blood at different ages, in as nuch as only 3% of it passes to the brain (28). The blood concentration of tryptophan also decreased throughout postnatal development up to day 15 (unpublished results). This seems to indicate that there is a relationship between tryptophan in the HP and in the blood. It is know that tryptophan is mostly metabolized by the liver via the tryptophan pyrrolase. This enzyme is induced during the first month of rat life (29). The induction of this metabolic pathway could produce the decrease in tryptophan in the blood. Our results show that 5-HT increased during the first month of life and NA increased during the first three months, which seem to indicate that as in other brain structures (30-32) the development of NA and 5-HT is predom:nantly a postnatal event. Likewise, it has been reported that specific binding of ?HX-HT increased by more than 25cpb in the HP between the first week and the third month after birth (33). Serotoninergic ascending prelections arising frcxn raphe medialis and dorsalis nuclei spread inhibitory inpulses all over the hippocanpal fields, especially in hippocaapal pyramidal cells (34). The 5-HT increased during aging and being signif icant from 6 to 24 increased synthesis, months, it nay reflect decreased catabolism or both. Our results indicate that there is an increase in the 5-HT -synthesis, since the 5-HT:5-HIAA ratio ws increased in this period. NA and its metaboli te M-K did not change during aging. However, a significant loss in the noradrenemic metabolitx (4-nxethmpc recently, J 3-hydr&yphenylgiycol) MS observed in AlzheimerzTyPe dementia (35). lt is possible that changes in the NA metabolism only occur in some diseases, but not during no-1 aging. hibreover, these observations in tk nor-erg&r system ascribed to Alzheimer’s disease have to be interpret-d with cautim since it has been found that anirwl brains with areas of chabinergic darmge are innervated by noradrenergic fibres (36). ACKNOWLEDGMXI This work MS supported by CAICYT nQ 1029184. M. Santiago is a recipient of a predoctoral Fond0 de Invest igaciones Sani tarias.
fellowship
from I. I.E.
de1
2508
Biogenic
Amines in Rat Hippocampus
Vol.
42,
No. 24,
1988
REFERENCES 1. R.T. BARTUS, R.L. DEAN, B. BEER and A.S. LIPPA, Science 217 408417 (1982). 2. F.H. GAGE and J .E. SPRINGER, Phanmcol . Biochem. Behav. 14 815-821 (1981). 3. L.L. LIGHT and P.A. ANDERSON, J. Gerontol. 40 737-747 (1985). 4. P.L MXEER, Can. J. Physiol. Pham~col. 62 741-754 (1984). 5. E.C. AZMITIA, Handbook of Psychophamacology, vol. 9, p. 233, Plenum Press, New York (1978). 6. F. FONNUMand J. S’IDRN-MATHISEN, Handbook of Psychophamcology, vol. 9, p. 357, Plenum Press, New York (1978). 7. P.R. LEWIS and C.C.D. SHUTE, Handbook of Psychc@amacology, vol.-g, p. 315 Plenum Press, New York (1978). 8. 0. LINDVALL and A. BJORKLUND, Handbook of Psychopharmacology, vol. 9, p. 139, Plenum Press, New York (19781. 9. K. ISHIKAWA, T. OTT and J.L. MXAUGH, Brain Res. 232 222-226 (1982). 10. A. PLAZNICK, W. DANYSZand W. KOSTowsKI, Physiol. Behav. 31 625-631 (1983)) 11. S.S. KETY, Res. Publ. Assoc. Res. Nerv. Ment. Dis. 50 376-389 (1972). 12. F.H. GAGE, R.G. THObf’sONand J.J. VALDES, Pharmccrl _ Eiochm. Behw+- 4 359-367 (1978). 13. CH. FLICKER and M.A. GEYER, Brain Res. Rev. 4 79-103 (1982). 14. M. PISA and H.C. FIBIGER, Brain Res. 272 319-329 (19831. 15. T.W. ROBBINS, B. J . EVERITT, B.J. COLE, T. ARCHERand A. MXIAMID, Pbysi ological Psychology 13 127-150 (1985). 16. M. SEGAL, Brain Res. 103 167-169 (1976). 17. G. WENT, D . HLKGHEY , V. BDUNDY, A. KIM, L . W!!KER and D . OLSON, Behav. Neurosci. 101 325-332 (1987). 18. S.E. ROBINSON, D. M%‘Il-IE-SORENSSEN, B.L WODDand J. COhrMISSIoME, J. Pham. Exp. Ther. 20 476-479 (1979). 19. E. COSTA, P. PANULA, M.K. THOk&‘RSON and D.L. CHENEY, Life Sci. 32 165-179 (19831. 20. A. MUHtUXI, J. CAN0 and M. SANTIAGO, Arch. Gerontol. Geriatr. 5 323-342 (19861. 21. I .N. AFFORD , M. GILBERG and J .D. BARCHAS, Anal. Biochem. 104 469-472 (1980). 22. C. KIM, C. CAM%NELLI and J .M. JHANNA, J. Chrotmtog. 282 151-159 Cl98i31. 23. B.H.C. WESTERINK, J. Liquid Cbmtog. 6 2337-2351 (19831. 24. H. HALLI&N and G. JONSSON, Brain Res. Bull. 13 383-389 (1984). 25. S. CHEIFETZ and J .J. WARSH, J. Neurochem. 34 1093-1099 (1980). 26. K. TACXZXJTI, M. LE MIAL and H. SIWN, Neurosci. Lett. suppl. 26 S332 (1986) 27. P.L. WCxDD,N.P.V. NAIR and W. E0ZARTH, Neurosci. Lett. 32 291-294 el9822,. 28. H.M. VAN PRAAG and C. LEMIS, Nutrition and the Bmin, vd. 7, P. 89, Raven Press, New York (19831. Chem. 252 43%436Q Pl9771. 29. M.D. ROPER and J.M. FRANZ, J. Biol. 30. L.A. LOIZDU, Brain Res. 40 395418 (19721. 31. J . CAN0 and F. REIMXO-SUAREZ, Dev. Brain Res. 5 19!%201 (1982). Biogmic Amines 4 32. M. SANTIAGO, J. CANo, A. F&HNlO ad F. REIH)X)-!%AREZ, 137-145 (1987). Receptors for Neclro33. M. HAMlN, D.L. NELm, A. HERBERT and J . CXJWlNSKI, New York (1983). transmitters and Peptide Home. p- 223, Raven Press, 34. S.E. ROBINSON, Life Sci. 32 345-353 (1983). and Pathological 35. E.K. PERRY and R.H. PERRY, The Aging Brain, Physiological Aspects, p. 140, Springer-Verlag, Berlin, Heidelberg, New York (1982). 36. C.A. CRUTCHER and J.N. DAVIS, Trends Neurosci. 4 70-72 (1981).
Pergamon Press
CHANGESIN BICGENIC AMINES IN RAT HIPPKAhWS M. Santiagoa,
DURING DEVELOPMZNTAND AGING
A. Machadoa, F. Reinoso-Suirezb
and J. Canoa’Y
aDepartamento de Bioquimica. Facultad de Farrrncia. 41012-SEVILLA and bDepartamento de Morfologia. Facultad de Medicina. Universidad Aut6norra de h4drid. Spain. (Received
in final
form April
14, 1988)
SUMVWRY The effects of postnatal development and aging on the of dopamine, noradrenal ine, serotonin and their concentration principle metabolites have been studied in the hippocanpus of the rat. During development the concentration of dopamine increases 1.5 fold during the first 90 days. 3-methoxytyramine \nas found in low concentrations. The homovanillic acid and DOPAC concentrations showed no changes apart from a decrease at day 15 and an increase at day 8, respectively. Fran birth up to 30 months, the noradrenaline concentration increased by a factor of about 10. Their metabolites each showed a different profile. The concentration of tryptophan \k~s almys the highest amcng the conpounds studied. It decreased f ran birth to day 15, while the concentration of serotonin and 5_hydroxyindolacetic acid increased 3 and 5 fold respectively during this time. However, 5_hydroxyt ryptophan and 5-hydroxyttyptophol concentrations were very low and unchanged at all stages. These findings led to the conclusion that the neurotransmitters: noradrenaline and serotonin, are developed in the hippocanpus during the first three months. During aging, the serotonin concentration is increased without significant change in the other conpounds studied. The hippocanpus (HP) plays an irrportant role in short term memory (1) and locomotor activity (2). The memory changes or losses during a life time are due to the nom1 aging process (3) and occur even more rapidly when senile dementia occurs (4). It is kn0v.n that axons containing dopamine (DA), noradrenal ine (NA) , serotonin 6HT), as well as other neurotransmitters, converge in the HP (5-9). Sune research has been carried out in order to clarify the role of hippocarrpal NA and 5-HT. The underlying assumption is that the HP rrny be the integrating structure for the expressian of NA and S-HT effects an behaviour (10). It has been suggested that the brain NA is involved in some motor activity mechanisms such as: theta rhythm generation and modulation of the hippocanpal in response to behaviourally significant stirmli, coding for non-rekard, learning and memory (11-13). At the same time, several reports have questioned tiether the locus coeruleus system is involved in attention, learning or memory (14,151. In most of these phenomena NA plays a facilitatory role.
*
To Tom all
correspondence
shmld
be addressed.
0024-3205/88 $3.00 + .OO Copyright (c) 1988 Pergamon Press
plc
2504
Biogenic
Amines in Bat Hippocampus
Vol.
42, No. 24, 1988
I&h less is larom about the role of the hippocanpal serotaninergic system. There is evidence that serotonin has an inhibitory ef feet on the activity of the hippocaspal neurons, motor activity, learning and memory and pain perception (2,161. Pathological changes in the raphe system may al so inpair memory (17). The HP is a brain region with a relatively small dopaminergic innervation. The dopaminergic activity is layoff to be involved in the septo hippocanpal path-y (18,191. The aim of this work v.ns to study the behaviour of DA, NA and 5-HT and the concentrations of their main metabolites (3_methoxytyramine, 3-MT; 3,4-dihydroxyphenylacetic acid, DOPAC; hanovanillic acid, HVA; 3-methoxy-4- hydroxyphenylglycol , M-K; normetanephrine, NM; metanephrine, MJ; tryptophan, ttyp; 5-hydroxyttyptophan, 5-HTP; 5-hydraxyindolacetic acid, 5-HIAA; and 5-hydroxy5-HTOL) during the developmental and aging periods in the HP of t ryptophol, the rat, in order to understand changes and look for some correlation between behavicur changes described during this period.
The performed
measurement of the biogenic according to methods described
amines and their elsewhere (20).
metabolites
was
Cur study was performed on male rats of the Wi star strain. These were maintained on a 12-h dark/l2-h light cycle and allowed free access to food and wnter. The anirrals at all stages were decapitated between 10.00 and 11.00 a.m. and the whole brain \nas quickly removed and dissected at OK using a A cut was made thrash the corpus callosum and the dissecting microscope. cortex ms peeled back exposing the HP which MIS carefully removed. Statistical analyses: behavioural data were treated variance (Snedecor’s F-test). Observed mean differences Tuckey’s t-test.
via analysis of the were evaluated with
RESULTS Table I shows the content of DA and its metabolites. The DA underwent a increase between days 0 and 90, but withat any statistically slight significant differences during any of the stages studied. The adult level (3 months) found was in relatively good agreement with those obtained by other authors (21,221. During development and aging, 3-MT had the lowest concentration of any DA metabolites studied (ranging between 4.1 and 10.9 nglg wet tissue) and was not detectable at birth. DOPAC and HVA developmental profiles were different during the first stages of development. COPAC underwent a significant increase fran day 0 to day 8 (287.fX, PcO.05, Tuckey’s t-test), HVA underwent a decrease at day 15 (41.4%). However, among while in contrast, DA metabolites only the DOPAC showed a statistical change. The amount of NA and its metabolites found in the HP is presented in table II. This catecholamine underwent an increase during postnatal development up to 3 nxxtths. When the first stages (0, 8, 15 and 30 days) are curpared with the others (1, 3, 6, 12, 24 and 30 months) they show statistically significant changes (table II). There were no statistical differences after 3 The NA concentration found in the adult rat (3 nuxlths.1 conpares mxlths. favorably with that reported by other investigators (21-24).
Biogenic
Vol. 42, No. 24, 1988
2505
Amines in Rat Hippocampus
TABLE I Concentration
of Dopamine and its Age in days 8 15
0
Metabolites
in the Rat Hippocanpus.
3
30
6
Age in months 24 12
30
DA
16.0 *1.2 (6,
17.4 +1.1 (6)
18.7 22.1 (10)
21.0 il.2 (7)
24.3 k3.5 (4)
19.5 *1.0 (5)
19.8 kO.4 (4)
20.3 +1.8 (4)
20.6 k3.6 (4)
3-W
n.d.
7.9 +0.7 (4)
8.3 *0.7 (4)
8.0 +0.6 (6,
10.9 kO.6 (4)
10.3 fl.1 (4)
7.1 kO.3 (4)
8.8 *0.8 (4)
4.1 +o.g (4)
DOPAC
5.4 *o. 7l (4)
20.9 20.6 (61~
19.2 *1.1 (lOI3
20.6 +1.3 (514
13.8 k1.6 (4)
15.5 k0.6 (5)
9.6 f0. 75 (4)
10.7 *1.26 (4)
12.9 *0.7 (4)
HVA
27.9 Zt1.1 (6,
27.5 f1.4 (4)
16.1 +1.6 (4)
14.5 kO.8 (5)
16.7 k2.8 (4)
21.5 +2.0 (6)
15.6 *3.5 (4)
16.3 *1.9 (4)
17.6 *1.3 (4)
Results are given in rig/g wet tissue as mean + SEM for the nurrber of animals in parentheses. n.d.= not detectable. Behavioural data were analyzed by ANOVA. (Tuckey’s t-test): 2-4 vs . 1,536., P
of Noradrenaline Age in days 15 8
32.8 *2.S1 (6,
59.0 i2.72 (5)
74.5 *2.S3 (12)
n.d.
19.3
21.4
n.d.
n.d.
and its
30
3
163.9 +9.g4 (7)
316.8 k12.5 (415
29.3
Metabolites b
in the Rat Hippocanpus.
Age in months 12 24
30
283.5 *11.76 (6,
290.8 *6. g7 (4)
306.6 *lo. 3 (4?
324.5 *13.0g (4)
53.8
56.8
64.3
45.9
47.4
‘;;‘;12
*;;;13
*;;;14
4.4 *0.6 (4,18
8.0
19.4
27.8
24.4
27.6
30.0
20.8
‘&‘;19
*:;;20
‘$$21
*;;;22
+:4;23
+;4;24
*;$25
n.d.
n.d.
n.d.
3.1 *0.4 (4)
6.4 kO.6 (4)
8.9 1tO.6 (4)
8.1 20.9 (4)
7.6 Al.0 (4)
Results are given in rig/g wet tissue in parentheses. n.d.= not detectable.
as mean f SEM for the nutiber of animals Behavicural data were analyzed by MVA. 4,8,9 10,ll Statistical significance (Tuckey’s t-test): 4 vs. l-3; 5 vs vs. 13-17; 12 vs 16,17, 18 vs 21-25, 19 vs 23,24,) P
None of NA metabolites studied were detectable at birth. M-KG WIS found to have the highest concentration, and at day 8 and 15 showed statistical changes hen ccrrpared with day 90 cnv,ards. NM showed a behaviour similar to MPG. W was not f-d in detectable levels up to 3 months, and the level rained very low during aging (ranging between 3.1 and 8.9 nglg wet tissue).
Biogenic
2506
Amines
in
Rat Hippocampus
Vol.
42,
No.
24,
1980
As can be seen from table III, the concentration of tryptophan was found It underwent a decrease during development up to day 15 to be the highest. (65.696, PcO.05, as coqared with day 0). From day 15 onwards no statistical differences were found. The 5-HTP was not detectable up to 3 months and, after its concentration was very low during all stages studied (ranging that, between 3.6 and 6.0 nglg wet tissue). The 5-HT continued to increase throughout (table III). With respect to 5_HIAA, the nain 5-HT metabolite, the three first stages (0, 8 and 15 days) showed some statistical changes as conpared with other stages. Thereafter, it renained without statistically significant changes, apart fom differences observed when conparing levels at 30 days with those at 24 (45.896, P
TABLE II1 Concentration
Age 8
0 Trvu aL 5-HTP
8615.4 k379.4 (6+ n.d.
5-HT
78.5 ‘$0
5-HIAA
5-HTOL
of
2963.8 k100.1 (413
its
Metabolites
2930.0 k132.7 (414
n.d.
n.d.
138.5
181.8
238.6
:70;12
*&;13
202.6
3 3100.4 ?69.25 (4)
2454.1 ?126.B6 (5)
6.0 +o.g (4)
4.7 kO.5 (4)
264.5
259.1
*:;;14
+;6;20
$~21
?$;22
10.1 +1.1 (4)
10.4 +-0.9 (4)
7.8 kO.7 (4)
8.9 kO.5 (8)
10.1 fl.1 (4)
22
253.1
nglg wet tissue not detectable.
,
l
vs. 26,27;
2284.5 ?127.67 (41
2528.6 *47.g8 (4)
3.6 +0.3 (4)
5.7 kO.7 (4)
21 v,.
30 2425.1 +67. 3g (4) 6.0 fl.1 (4) 358.1
346.7 512.5 +22. B16 - f4) ‘T&7
“:;:18 379.5
319.8
+2:4:24
+2;$25
+$;26
+~$27
8.3 +0.6 (4)
10.0 kO.5 (4)
9.1 fl.1 (4)
7.4 +1.2 (4)
as means * SEM for
4,&g;
Hippocanpus.
285.2
Behavioural 1 (Tuckey’s t-test )* 13,15 vs 16,18. 17 vs
26127: p
Rat
in months 12 24
*;;;15
*:&-;19
significance 11 13-15; vs.
the
6
318.1 +34.6 - f4,23
113.5
in Age
30
n.d.
*;6;11
58.6
Statistical 12,14,15; 10_13;15;
and
in days 15
5155.4 k442.2 (61~
Results are given in in parentheses. n.d.=
23-26:
Serotonin
data
10’ 27;
P
369.0
the number of anirral s
were
analyzed
by ANoVA.
Vol.
42, No. 24, 1988
Biogenic
Amines in Bat Hippocampus
2507
DISCUSSION The HP has been identified as critical for the mediation of normal memory. It has been reported that dopaminergic neurons could have a modulatory (26). As our results show DA, as well as its influence on memory processes DOPAC, HVA and 3-MI’ are not markedly modified, thagh I-WA levels metabolites, It is to be noted that at birth the DA content WLS very decrease slightly. was similar to that of the adult. This seems to suggest that the DA path-y more developed at birth than those of the NA and 5-HT. Though, at present it is not safe to conclude that a change in any of the metabolites reflects a it roust be kept in mind that 3-MI levels are variation in DA neuron activity, cannonly considered as a reliable indicator of DA release (27). Therefore, our results point tmrds the lack of changes in hippocarrpal dopaminergic activity and release during development and aging. were the highest found. They underwent a concentrations Tryptophan statistical decrease throughout the developmental period, nrtinly during the first fifteen days. The changes in tryptophan in the brain could be related to the tryptophan concentration in the blood at different ages, in as nuch as only 3% of it passes to the brain (28). The blood concentration of tryptophan also decreased throughout postnatal development up to day 15 (unpublished results). This seems to indicate that there is a relationship between tryptophan in the HP and in the blood. It is know that tryptophan is mostly metabolized by the liver via the tryptophan pyrrolase. This enzyme is induced during the first month of rat life (29). The induction of this metabolic pathway could produce the decrease in tryptophan in the blood. Our results show that 5-HT increased during the first month of life and NA increased during the first three months, which seem to indicate that as in other brain structures (30-32) the development of NA and 5-HT is predom:nantly a postnatal event. Likewise, it has been reported that specific binding of ?HX-HT increased by more than 25cpb in the HP between the first week and the third month after birth (33). Serotoninergic ascending prelections arising frcxn raphe medialis and dorsalis nuclei spread inhibitory inpulses all over the hippocanpal fields, especially in hippocaapal pyramidal cells (34). The 5-HT increased during aging and being signif icant from 6 to 24 increased synthesis, months, it nay reflect decreased catabolism or both. Our results indicate that there is an increase in the 5-HT -synthesis, since the 5-HT:5-HIAA ratio ws increased in this period. NA and its metaboli te M-K did not change during aging. However, a significant loss in the noradrenemic metabolitx (4-nxethmpc recently, J 3-hydr&yphenylgiycol) MS observed in AlzheimerzTyPe dementia (35). lt is possible that changes in the NA metabolism only occur in some diseases, but not during no-1 aging. hibreover, these observations in tk nor-erg&r system ascribed to Alzheimer’s disease have to be interpret-d with cautim since it has been found that anirwl brains with areas of chabinergic darmge are innervated by noradrenergic fibres (36). ACKNOWLEDGMXI This work MS supported by CAICYT nQ 1029184. M. Santiago is a recipient of a predoctoral Fond0 de Invest igaciones Sani tarias.
fellowship
from I. I.E.
de1
2508
Biogenic
Amines in Rat Hippocampus
Vol.
42,
No. 24,
1988
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