Specifically affected, are dopamine transporters which are presynaptic on the nigrostriatal cells. SPECT is used to detect these abnormalities in Dopamine transporters. Given that many patients have asymmetrical loss of function and metabolism this can help differentiate patients with CBD and those with Alzheimers.SPECT studies of individuals diagnosed with CBD involve perfusion analysis throughout the parts of the brain. SPECT evaluation through perfusion observation consists of monitoring blood release into different locations in tissue or organ regions, which, in the case of CBD, pertains to localized areas within the brain. Tissue can be characterized as experiencing overperfusion, underperfusion, hypoperfusion, or hyperperfusion. Overperfusion and underperfusion relate to a comparison with the overall perfusion levels within the entire body, whereas hypoperfusion and hyperperfusion are calculated in comparison to the blood flow requirements of the tissue in question. In general, the measurements taken for CBD using SPECT are referred to as regional cerebral blood flow (rCBF).In general, SPECT reveals hypoperfusion within both the posterior regions of the frontal and parietal lobes. As in images gathered through MRI, SPECT images indicated asymmetry in the presentation of abnormalities throughout the brain. Additional studies have revealed the presence of perfusion anomalies in the thalamus, temporal cortex, basal ganglia, and pontocerebellar (from the pons to the cerebellum) locations within subjects brains. FDOPA PET
Research has suggested that the integrity of the dopamine system in the striatum has been damaged as an effect of CBD.
It is thought that bimatoprost mimics the human bodys own prostamides (which are chemically similar), a class of substances related to prostaglandins, but with an unknown mechanism of action. No prostamide receptor has been identified as of 2015; the search is ongoing. As of 2019 it was thought that bimatoprost worked via the trabecular meshwork and uveoscleral pathways. Pharmacokinetics
Bimatoprost is well absorbed through the cornea. It starts lowering intraocular pressure after four hours, lasting for at least 24 hours. A low percentage enters the bloodstream. In the blood plasma, peak concentrations are reached after 10 minutes, then drop below the detection limit of 25 pg/ml after 1.5 hours. The substance does not accumulate in the body.Plasma protein binding is 88%. Bimatoprost is metabolized by oxidation, N-deethylation and glucuronidation, forming a variety of metabolites. Biological half-life was measured to be 45 minutes after intravenous infusion. 67% are eliminated via the kidney, and 25% via the feces. References
Further reading
"Prostaglandin Analogues for Ophthalmic Use: A Review of the Comparative Clinical Effectiveness and Cost-Effectiveness". CADTH Rapid Response Reports. July 2015. PMID 26985536. External links
"Bimatoprost". Drug Information Portal. U.S. National Library of Medicine.