Thesis (PhD (Biomedical Sciences. Medical Physiology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Psychosocial stressors have frequently been associated with an increased risk for developing The contributions of the cholinergic (Lobeline) and opioid (Naltrexone) systems in place
preference behaviour were determined by employing a post-methamphetamine
pharmacological treatment strategy. These two treatments failed to reverse the
methamphetamine-induced place preference. However, administration of the drugs did lead to
alterations in striatal dopamine and serotonin levels which may infer beneficial effects against
the biochemical alterations induced by methamphetamine.
We used both 2-D gel-based proteomics and isobaric tagging for relative and absolute
quantitation (iTRAQ) to identify proteins in the frontal cortex, and nucleus accumbens shell
and core of rats that were subjected to maternal separation, methamphetamine or both
regimes. The proteins were associated with cytoskeletal modifications, altered energy
metabolism, degenerative processes, interruptions in normal neurotransmission and enhanced
intracellular signalling. We found that more proteins were quantitatively expressed in rats that
were exposed to maternal separation followed by methamphetamine treatment than those
animals subjected to the individual interventions independently. Additional proteins recruited
by the combination of MS followed by MA which remained unchanged with independent
treatments included malate dehydrogenase, V-type proton ATPase subunit E1, beta-synuclein,
brevican core protein, eukaryotic translation initiation factor 4H, histidine triad nucleotide
binding protein 1 and stress-induced phosphoprotein in the nucleus accumbens shell subregion.
Additional proteins recruited in the core subregion with the combination treatment
included thymosin beta-4, calretinin, Arpp-21 protein, alpha-synuclein, ubiquitin carboxylterminal
hydrolase isozyme L1, cytochrome c, brain acid soluble protein 1, prosaposin and
stress-induced phosphoprotein 1. Although, on a behavioural level via the use of CPP we
found that MS did not exacerbate the rewarding effects of MA, the proteomic data does infer
a role played by early life stress by the recruitment of additional proteins. We therefore
propose that the molecular mechanisms by which early adverse events predispose animals to
the addictive state may involve a complex assembly of cellular processes within the brain.
depression, anxiety or substance abuse in adult life. Animal studies have also suggested that
stressful experiences may result in altered behavioural responses to drugs of abuse as
evidenced by enhanced cocaine self-administration and psychostimulant-induced
hyperlocomotor activity.
The main aim of our study was to establish whether adversity early in life would render
individuals more vulnerable to later drug usage. We adopted maternal separation as our
animal model of early life adversity and treated these animals with methamphetamine during
the adolescent stage of their life. A conditioned place preference (CPP) paradigm was
subsequently used to determine the rewarding effects of methamphetamine. To obtain an
understanding of the underlying molecular mechanisms of methamphetamine-induced
behaviour, we measured neurochemical changes on a neuroendocrine, neurotrophic,
neurotransmitter and proteome level.
Firstly, we established that methamphetamine-induced place preference behaviour lasted for
at least 2 weeks after the last methamphetamine administration. Contrary to expectation, this
behaviour was not affected by prior exposure to maternal separation. However, rats subjected
to maternal separation caused a decrease in apomorphine-induced locomotor behaviour in
methamphetamine-treated rats. Maternal separation therefore preferentially affected the
behavioural repertoire of the dorsal striatum rather than that of the ventral striatum.
A general down regulation of neuroendocrine activity (ACTH and corticosterone levels) was
observed in animals subjected to maternal separation or methamphetamine treatment, as well
as those subjected to the combination of the two interventions. Increased concentrations of
plasma prolactin levels in maternally separated as well as normally reared animals subjected
to methamphetamine-CPP were found which suggested a reduction in dopamine inhibition.
Maternal separation resulted in increased NGF levels in the ventral hippocampus of
methamphetamine treated rats. This suggested that the ventral hippocampus may particularly
be vulnerable to the effects of early life stress. The increased neurotrophin concentrations may reflect a compensatory response to stress and drug exposure. / AFRIKAANSE OPSOMMING: Psigososiale stressors word gereeld geassosieer met ‘n verhoogde risiko vir die ontwikkeling
van depressie, angs en dwelm misbruik in volwassenheid. Diere studies het ook al bewys dat
vroeë lewensstres in die vorm van moederlike skeiding lei tot veranderde gedrag teenoor
dwelm misbruik. Hierdie veranderde gedrag veroorsaak deur moederlike skeiding sluit die
verhoodge kokaïne toediening en psigostimulant geinduseerde verhoging in lokomotoriese
aktiwiteit in.
Die hoofdoel van die studie was om vas te stel of vroeë lewensstres mense meer vatbaar laat
vir latere dwelm misbruik. ‘n Moederlike skeidings diere model was gebruik om vroeë
lewensstres voor te stel and het verder hierdie diere behandel met metamfetamiene gedurende
adolesensie. Die gekondisioneerde plek voorkeur model was gebruik om die euforiese /
verslawende effekte van metamfetamiene te bepaal. Om die onderliggende molekulêre
meganismes van metamfetamien geinduseerde gedrag te verstaan het ons neurochemiese
veranderinge op ‘n neuroendokriene, neurotrofiese, neurotransmissie en proteinvlak vasgestel.
Eerstens het ons was gestel dat metamfetamien geinduseerde plek voorkeur vir ten minste
twee weke na die laaste metafetamien toediening voortduur. In teenoorstelling met
verwagting, het moederlike skeiding nie metamfetamien geinduseerde plek voorkeur
beinvloed nie, maar eerder apo-morfien geinduseerde lokomotoriese aktiwiteit geaffekteer.
Moederlike skeiding stres het by voorkeur die gedrags funksie van die dorsale striatum
beinvloed eerder as die ventrale gedragsfunksie.
‘n Algemene afregulering van neuroendokriene aktiwiteit was waargeneem
(adrenokortikotrofiene en kortikosteroon vlakke) in diere wat aan moederlike skeiding of
metafetamien behandeling sowel as die kombinasie behandeling blootgestel was. Verhoogde
plasma prolaktien vlakke was gevind in moederlike skeidings rotte sowel as kontrole diere
wat verder blootgestel is aan metamfetamien behandeling wat ‘n inhibisie van die dopamiene
sisteem toon.
Moederlike skeiding het ook ‘n verhooging in neurotrofiene (NGF) in die ventrale
hippokampus van metamfetamien behandelde rotte veroorsaak. Hierdie bevinding stel voor
dat die ventrale hippokampus veral vatbaar is vir die effekte van vroeë lewensstres. ‘n Verhoging in neurotrofien konsentrasies mag ‘n kompenserende teenslag van die brein wees
teen stres en dwelm blootstelling.
Die bydrae van die cholinergiese (Lobeline) en opiaat (Naltrexone) sisteme in plek voorkeur
gedrag was bepaal deur farmaseutiese behandeling te volg na metamftemien toediening.
Lobeline en naltrexone was egter nie suksesvol om die metamfetamien geinduseerde plek
voorkeur te wysig nie. Alhoewel die toediening van die twee behandelings het tot
veranderinge in neurotransmissie (dopamiene en serotoniene) gelei wat moontlik tot
voordelige effekte teen die biochemiese veranderinge van metamfetamien kan lei.
Om veranderinge op proteinvlak in die frontale korteks en nukleus akkumbens middel en
buitenste subareas vas te stel het ons gebruik gemaak van twee-dimensie gel elektroforese en
isobariese merkers vir relatiewe en absolute kwantifisering (iTRAQ) gevolg deur massa
spektrofotometrie. Geindentifiseerde proteine was geassosieer met sitoskeletale modifikasies,
veranderde energie metabolisme, afbrekende prosesse, onderbrekings met normale
neurotransmissie en intrasellulêre seintransduksie. Meer proteine was beduidend in die diere
wat aan beide moederlike skeiding en metamfetamien behandeling blootgestel was.
Addisionele proteine wat deur die kombinasie behandeling geaffekteer is in die buitenste
subarea van die nukleus akkumbens sluit ‘malate dehydrogenase’, ‘V-type proton ATPase
subunit E1’, ‘beta-synuclein’, ‘brevican core protein’, ‘eukaryotic translation initiation factor
4H’, ‘histidine triad nucleotide binding protein 1’ en ‘stress-induced phosphoprotein’ in.
Additionele proteine geaffekteer in die middelste subarea van die nukleus akkumbens sluit
‘thymosin beta-4’, ‘calretinin’, ‘Arpp-21 protein’, ‘alpha-synuclein’, ‘ubiquitin carboxylterminal
hydrolase isozyme L1’, ‘cytochrome c’, ‘brain acid soluble protein 1’, ‘prosaposin’
en ‘stress-induced phosphoprotein 1’ in. Vanuit ‘n gedrags benadering deur die gebruik van
metamfetamien geinduseerde plek voorkeur het moederlike skeiding nie diere meer vatbaar
gemaak vir die effekte van metamfetamien nie, maar die protein data wys wel dat vroeë
lewens stres ‘n rol speel deur dat meer proteine geaffekteer word deur die kombinasie van
moederlike skeiding gevolg deur later metamfetamien toediening. Ons stel voor dat die
molekulêre meganismes waardeur vroeë lewensstres diere meer vatbaar maak vir die
verslawende effekte van stimulante behels ‘n komplekse samestelling van sellulêre prosesse in die brein.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/3189 |
| Date | 03 1900 |
| Creators | Faure, Jacqueline Jeanette |
| Contributors | Daniels, W.M.U, Stein, D.J, University of Stellenbosch. Faculty of Health Sciences. Dept. of Biomedical Sciences. Medical Physiology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
Page generated in 0.0538 seconds