PubMed · 5005925
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C J Witkop. 1971. Albinism.. https://pubmed.ncbi.nlm.nih.gov/5005925/
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The aim of this study was two-fold: 1) To provide in DA-HAN rats the basic brain monoamine data useful for later investigations of the neurochemical effects of sensory alterations and 2) to assess whether there is a relationship between the monoaminergic pattern in medial vestibular nuclei and optokinetic performances. We comparatively studied the regional brain monoamine distribution and the optokinetic performances in pigmented DA-HAN and albino Sprague-Dawley rats. As expected, the optokinetic responses and vestibulo-ocular reflex gain were by far more efficient in DA-HAN rats. Norepinephrine (NE), dopamine (DA), serotonin (5-HT) and their metabolites were determined in retina, brainstem nuclei and dopaminergic areas. DA-HAN rats exhibited an increased noradrenergic activity in the medial vestibular nuclei, locus coeruleus and anteroventral cochlear nucleus, an extended decrease of serotonergic activity in brainstem nuclei and increased DA stores with a reduced dopaminergic activity in most dopaminergic areas. These data confirm and extend the general findings that biochemical data obtained in one strain cannot be extrapolated to another strain. The possible role of the morphological neuronal abnormalities and functional impairment induced by albinism has been discussed especially in medial vestibular nucleus, cochlear nuclei and retina. Alternatively, behavioral factors may also explain some of the observed neurochemical differences.
Albinism connotes a large group of genetic disorders that are characterized by diminished ocular and oftentimes cutaneous pigmentation. These disorders are generally subclassified as oculocutaneous albinism (OCA) or ocular albinism (OA) based on the extent of their effects on the pigmentation of the skin and hair. Sometimes, different mutations in the same gene can cause OCA or OA.
Choroidal blood flow is one of the highest in the body on a global volume basis. Little is known, however, about flow through individual vessels, which has important consequences for ocular blood delivery and oxygen transport. The purpose of this study was to use a new epifluorescent technique to view, record, and quantify erythrocyte (RBC) flow in individual rat choroidal vessels through the intact sclera. With the Sprague-Dawley rats under urethan anesthesia, rhodamine-labeled liposomes were injected intravenously and served as a plasma marker. Rat RBC were labeled ex vivo with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate and then infused intravenously. The flow of the fluorescent RBC through 69 choroidal vessels with diameters between 12 and 52 microm in six rats was recorded on videotape, and the images were used to determine vascular diameter, RBC flux and velocity, and microvessel hematocrit (Hct). RBC flux and RBC velocity were positively correlated with vessel diameter (r = 0.67, P < 0.001 and r = 0.29, P = 0.016, respectively). Microvascular Hct ranged between 4 and 32% (8 and 67% of systemic Hct) and was negatively correlated with diameter (r = -0.28, P = 0.018). The relationships of RBC flux and RBC velocity with vessel diameter were the same as found in other tissues. However, in other vascular beds, microvascular Hct and diameter are positively correlated. Because microvascular Hct is a determinant of relative viscosity and oxygen delivery, this relatively high Hct in small choroidal vessels could have significant implications for local blood flow and oxygen transport.