No description available.

No description available.

published_or_final_version / Zoology / Master / Master of Philosophy

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 6 uppsatser.

No description available.

No description available.

The nuclei of the midline thalamus are an important part of the brain’s limbic system. Previous work has described the presence of dopamine D2 receptors in the midline thalamus in humans, non-human primates, and rodents. A similar body of literature has also demonstrated dopaminergic innervation of the midline thalamus across these species. However, little is known regarding a) the source of dopaminergic innervation to the midline thalamus in rodents and b) the function of D2R in the midline thalamus in any species. I begin this thesis with a review of the literature examining the anatomy, electrophysiological properties, and role in behavior of the paraventricular nucleus of the thalamus (PVT), a region where D2R mRNA and protein is expressed. I next describe a series of three sets of experiments aimed toward examining the anatomical, electrophysiological, and behavioral role of D2R in the PVT in mice. In the first set of experiments, I used anatomical methods to show that D2R are particularly enriched in neurons of the PVT. I focused on D2R-expressing PVT neurons specifically and show their afferent and efferent projections throughout the brain. In addition, I describe a set of experiments aimed to establish a dopaminergic innervation to the PVT. In the second set of experiments, I used electrophysiological methods to study D2R-expressing PVT neurons. Here, I establish that tonic firing in D2R-expressing thalamic relay neurons in the PVT is inhibited by quinpirole, a D2R/D3R agonist, and increased by sulpiride, a D2R/D3R antagonist. In the third set of experiments, I assessed the behavioral function of D2R in PVT neurons since this has never been studied in any species. I directly manipulated PVT D2R in two directions: a) by overexpressing D2R, and b) by downregulating D2R. Here I show PVT D2R plays a role in both cocaine locomotor sensitization as well as contextual fear expression. Our findings demonstrate for the first time the role of D2R in the PVT and add to literature suggesting that the PVT is an important component of the neural circuitry underlying fear behavior and drug reward. I conclude this thesis with a discussion of the findings described in the three sets of experiments as well as a proposal for future experiments.

Not available / text

No description available.

It is well established that chronic treatment with neuroleptic agents which selectively block dopamine (DA) receptors in the brain leads to the development of DA receptor supersensitivity. However comparing the degree and duration of the changes in receptor sensitivity obtained by different investigators has been extremely difficult, because of the numerous differences that exist in individual methods of producing and examining DA receptor supersensitivity. By examining the DA receptor supersensitivity that ensues following chronic treatment with different doses and durations of pimozide, at various intervals after withdrawal from treatment, the overall parametric changes can be more directly compared. To measure the changes in DA receptor sensitivity following chronic pimozide treatment, both behavioral (d.-amphetamine-induced locomotor activity; apomorphine-induced stereotypy) and biochemical (DA receptor binding assay) techniques were utilized. With increasing doses of chronic pimozide treatment, the degree and duration of the resulting DA receptor supersensitivity increased as measured both behaviorally and biochemically. Similarily, the longer durations of chronic pimozide treatment had a greater effect on the degree and duration of the increased DA receptor sensitivity than did the shorter durations of treatment. Correlations were found between the biochemical and behavioral results both between groups of animals treated chronically with different doses and durations of pimozide and within individual groups of animals. In addition, the changes in receptor sensitivity following chronic pimozide treatment was due to an increase in the number of DA receptors with no change in the affinity of these receptors to DA. These results following chronic treatment with neuroleptics demonstrate that the behavioral supersensitivity observed in animals in response to either the direct DA agonist apomorphine or the indirect DA agonist d-amphetamine, may be a result of an increased number of DA receptors. Finally, the supersensitive DA receptors that develop as a result of chronic treatment with neuroleptics are discussed with regard to their possible relevance as an animal model of the iatrogenic disease, tardive dyskinesia, observed clinically in schizophrenic patients withdrawn from neuroleptic therapy. / Medicine, Faculty of / Graduate