Thesis (MSc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: SEPARATION STUDY
Traumatic experiences during childhood can have a negative impact on behaviour
later in life. Kendier et al. (1992) found that the loss of a parent during childhood
increased the risk to develop major anxiety disorders and could also lead to
depressive-like behaviour (Furukawa et al., 1999).
Methods:
We subjected rat pups to maternal separation and determined the effects thereof on
adult behaviour. We removed rat pups from their mothers for 3 hours daily from
postnatal day 2 to 14. On day 60, the behaviours of the rats were tested using the
elevated plus-maze and the open field test. Controls were reared normally.
Behaviours: Amount of time spent and the number of entries into the arms of the
maze were noted on the elevated plus-maze, while the total time spent in each zone
(inner versus outer) and the number of zone crossings were noted for each rat on the
open field arena. The latency to move from the initial placement in the outer zone to
the inner zone as well as the number of quadrant crossings was also determined.
Defecation, freezing, rearing and grooming behaviours were also noted.
Neurotransmitter levels: Noradrenaline, serotonin and their metabolites were
evaluated in maternally separated rats and compared to controls. Their concentrations
at basal level, immediately after restraint stress and 15 minutes after restraint stress,
were also determined. A HPLC method was followed in these determinations. ACTH Determinations: All rats were subjected to restraint stress for a lO-minute
period. Trunk blood was collected for basal, as well as 15 and 60 minutes postrestraint
stress for ACTH determinations.
Results:
Behaviours: The amount of entries was significantly reduced in the separated
animals, indicating decreased locomotion. They spent significantly more time in the
closed maze arms. A significant increase in defecation frequency and rearing
behaviour was noted. These observations are typical of anxious behaviour. In the
open field test, the behavioural results were less convincing. Only a significant
increase in defecation frequency and a significant decrease in rearing behaviour in
separated animals, were observed.
Neurotransmitter levels: No significant differences were noted between separated
animals and controls with respect to basal monoamine levels. However,
noradrenaline levels were significantly decreased in the frontal cortex 15 minutes
after restraint stress and immediately after restraint stress in the hypothalamus and
hippocampus in separated animals. MHPG levels were significantly decreased in the
frontal cortex immediately after restraint stress. No significant differences were
found with respect to serotonin levels. However, significant increases were found in
5HIAA levels in the frontal cortex and hippocampus of separated rats, 15 minutes
after restraint stress.
The basal turnover ratios of serotonin (5HIAA/5HT) and noradrenaline (MHPGINA)
did not yield significant results. However, immediately after restraint stress, a
significant increase was found in serotonin turnover in the hypothalamus of separated rats when compared to controls. This turnover rate was also increased in separated
rats, 15 minutes after restraint stress in the frontal cortex and hypothalamus.
ACTH Determinations: Basal ACTH levels were significantly higher in separated
animals. At 15 minutes post-restraint stress, the levels were significantly lower than
controls, indicating a blunted stress response.
Our results therefore showed that maternal separation could lead to anxious
behaviours in adult life. These behavioural abnormalities were associated with
alterations in the central nervous and neuroendocrinological systems, particularly in
response to stressful situations.
CRF STUDY
The maternal separation study indicated that elevated CRF levels could possibly be
causally related to abnormalities observed in the anxious animals. We therefore
hypothesised that adverse development factors, such as maternal separation,
predisposes individuals to develop psychopathologies later in life and that this
process was driven by a presence of high CRF levels.
Methods:
Cannulas were implanted into the left lateral ventricles of normal rats, making use of
stereotaxic procedures. CRF (3 flg/fll) was injected into the ventricles daily for 5
days. Saline controls were handled similarly, but only injected with saline for the same time period. Both groups of animals were then compared to naïve controls.
Histology was performed to determine the correct placement of the cannulas.
Behaviours: The Elevated Plus-maze was employed to determine whether their
behaviours were anxious. The number of entries into the various arms of the maze as
well as the amount of time spent in the open and closed arms was accumulated.
Rearing, freezing, defecation and grooming were also noted.
ACTH Determinations: The ACTH levels ofCRF-injected, saline-injected and naïve
rats were determined 15 minutes after restraint stress.
Results:
Behaviours: A decrease in the number of entries into the closed arms of the maze
was noted in the CRF-injected rats when compared to naïve controls. No significant
differences were found between the groups with respect to the amount of time spent
in the various arms and the behaviours noted during the experiment.
ACTH Determinations: A decrease in ACTH levels was noted in CRF-injected rats
15 minutes after restraint stress when compared to naïve controls. Therefore,
although the CRF injections did not alter the behaviour of the rat, they did exhibit a
blunted stress response to the stressor.
Conclusion:
Our experiments led us to conclude that early adverse experiences, such as maternal
separation, can lead to the development of psychopathologies later in life. CRF, however, is not pivotal in the development of these abnormalities; rather it seems that
the neurochemical abnormalities (serotonin and noradrenaline) play a more important
role in the development of these mental disturbances. Finally, we hypothesise that
combination drug therapy that targets both the noradrenergic and serotonergic
neurotransmitter systems could be preferred above those aimed at rectifying the
individual neurotransmitter systems in the treatment of psychopathologies, such as
anxiety disorders. / AFRIKAANSE OPSOMMING: MOEDERLIKE SKEIDINGS STUDIE
Traumatiese gebeurtenisse wat gedurende kinderjare ervaar word, kan 'n negatiewe
impak op die gedrag van dieselfde individue hê, as hulle volwassenheid bereik het.
Kendier et al. (1992) het waargeneem dat die verlies van 'n ouer tydens die
kinderjare, die risiko om angssteumisse te ontwikkel, dramaties verhoog en kan ook
lei tot 'n depressiewe gemoedtoestand (Furukawa et al., 1999).
Metodes:
Ons het neonatale rotte aan moederlike skeiding blootgestel en die effekte daarvan op
gedrag tydens hul volwasse lewe beoordeel. Ons het daagliks die moeders vir 3 ure
van die kleintjies afweggeneem, vanafpostnatale dag 2 tot 14. Op dag 60, het ons die
gedrag van die diere op die "elevated plus-maze" en die" open field test" getoets.
Kontrole rotte het onder normale omstandighede opgegroei.
Gedrag parameters: Die hoeveelheid tyd en aantal kere wat die rotte in die
verskillende arms van die "elevated plus-maze" gespandeer het, was waargeneem. Die
totale tyd in die "open field" toets se binneste ofbuitenste sones, die hoeveelheid
kruisings tussen die twee sones, die tyd wat dit neem om beweging in die binneste
sone te inisiëer, sowel as die hoeveelheid kwadrante wat gekruis was, is genotuleer.
Defekasie, botstilstande, steiering, en versorgingsgedragte was ook waargeneem
terwyl die rotte in die doolhowe was. Neurochemiese oordragstowwe: Die hippokampus, hipotalamus en frontale korteks
van moerderlik-geskeide rotte en kontroles, was uit hul brein gedissekteer om die
vlakke van noradrenalien, serotonien en hul metaboliete daarin te bepaal. Basale
vlakke sowel as hul konsentrasies onmiddelik na stres en 15 minute na stres, was
gedetermineer. 'n HPLC metode was gebruik vir hierdie bepalings.
ACTH bepalings: Rotte, moederlik-geskei en kontroles, was onderwerp aan
beperkingstres vir 'n tydsduur van 10 minute. Bloed was op die volgende
tydsintervalle gekollekteer vir die bepaling van ACTH vlakke, naamlik basaal, 15
minute en 60 minute na die einde van stresperiode.
Resultate:
Gedrag: Op die "elevated plus-maze" was moederlik-geskeide rotte minder
beweeglik omdat hul aanmerklik minder die arms van die doolhowe binne gegaan het.
Hulle het ook baie meer tyd in die geslote arms gespandeer. Verder het die
eksperimentele rotte meer defekasie bolusse uitgeskei en was die aantal steieringe
uitgevoer, ook aanmerklik verhoog. Hierdie patroon van gedrag is tipies die van
angstigheid.
Neurochemiese oordragstowwe: Daar was geen betekenisvolle verskil tussen die
basale neurotransmitter vlakke van moederlik-geskeide rotte en hul kontroles.
Daarenteen was die vlakke van noradrenalien in die frontale korteks dramaties
verhoog by die 15 minute tydsinterval na die stres, asook onmiddelik na die stres in
die hipotalamus en hippokampus. MHPG vlakke was egter aanmerklik verlaag in die
frontale korteks onmiddelik na die stres. Terwyl daar geen noemenswaardige verskil in serotonien vlakke waargeneem is nie, was die vlakke van 5HlAA betekenisvol
verhoog in die frontale korteks en hippokampus van moederlik-geskeide rotte, 15
minute na die beperkingstres. Geen verskil in die omsettingsverhoudinge van basale
serotonien (5HlAA/5HT) ofnoradrenalien (MHPGINA) vlakke is gevind nie. Daar
was egter 'n betekenisvolle verhoging in die serotonien omset in die hipotalamus van
moerdlik-geskeide rotte, onmiddelik na beperkingstres. Hierdie verskil het ook
voorgekom 15 minute na die stresperiode in die hipotalamus, sowel as in die frontale
korteks.
ACTH bepalings: Rotte wat onderwerp was aan moederlike skeiding het verhoogde
basale konsentrasies van ACTH getoon. Die ACTH vlakke was egter aanmerklik laer
15 minute na stres toe dit met kontrole groepe vergelyk is.
Ons resultate toon dus dat moerderlike-skeiding wel tot angstige gedrag tydens die
volwasse lewe kan lei. Hierdie afwyking in gedrag was geassosieër met
abnormaliteite in die sentrale senuwee sisteem sowel as die neuroendokrienologiese
sisteem van die dier, veralonder toestande van stres.
Na gelang van ons bevindinge in die moerderlike skeidingstudie, het dit geblyk dat
CRF 'n belangrike rol speel tot daarstelling van angstige gedrag. Daarom het ons in
die tweede deel van ons studie gaan kyk ofverhoogde vlakke van CRF in die brein
moontlik die gedrag van die rot kon verander. CRF STUDIE
Metodes:
Kannules was in die linker ventrikel van die breine van normale rotte geïmplanteer
deur gebruik te maak van stereotaktiese prosedures. CRF (3 Ilg/IlI) was daagliks vir 5
dae aan die rotte toegedien. Rotte wat presies dieselfde gehanteer was het 'n
fisiologiese soutoplossing ontvang. Hierdie rotte was met naïewe rotte vergelyk. Die
korrekte plasing van kannules was met histologiese metodes bevestig.
Gedrag: Die "elevated plus-maze" was gebruik om te bepaal of angstige gedragte
by behandelde rotte ontlok was. Die aantal kere wat 'n rot die verskillende arms van
die doolhofbinne gaan, sowel as die tyd wat die dier op elke arm deurbring was
genotuleer. Die aantal steierings, botstilstande, defekasies en versorgingsbewegings
was weereens waargeneem.
ACTH bepalings: Die vlakke van ACTH was bepaal in al die rotgroepe, 15 minute
nadat hulle aan 10 minute beperkingstres onderwerp was.
Resultate:
Gedrag: Rotte wat met CRF toegedien was, het op minder geleenthede die toe arms
van die "elevated plus-maze" binne gegaan toe hulle met die naïewe groep rotte
vergelyk was. Hierdie verskil was betekenisvol. Daar was geen ander
noemenswaardige verskille ten opsigte van die ander gedragsparameter nie. ACTH bepalings: Daar was 'n afname in die ACTH vlakke, 15 minute na die stres
toegedien was in rotte wat CRF ontvang het, in vergelyking tot die naïewe kontrole
groep.
Hierdie resultate dui daarop dat die toediening van CRF in die brein nie die rot se
gedrag, maar wel die dier se respons op stres, beïnvloed het.
Gevolgtrekking:
In die lig van die voorafgaande resultate verky, blyk dit dat moederlike-skeiding
tydens die vroeë kinderjare wel kan aanleiding gee tot angstige gedrag tydens
volwassenheid. Ons studies dui ook aan dat CRF nie die primêre bron van hierdie
gedrags afwykings is nie, maar dat abnormaliteite in die neurochemiese
oordragstowwe (serotonien en noradrenalien) eerder die bepalende faktore is. Ten
slotte, ons beveel aan dat geneesmiddels wat geskoei is om die serotonerge sowel as
die noradrenerge sisteme aan te spreek, voordeel moet geniet in die behandeling van
gedragstoomisse, soos angs.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52567 |
| Date | 12 1900 |
| Creators | Pietersen, Charmaine Y. |
| Contributors | Daniels, W. M. U., Stein, D. J., Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 96 p. : ill. |
| Rights | Stellenbosch University |
Page generated in 0.0029 seconds