Abstract
Purpose: :
To determine changes in levels of GABA, dopamine, glutamate, and GFAP in zebrafish retinas exposed to alternating hyperglycemic conditions for up to 2 months.
Methods: :
Adult, wildtype zebrafish were made hyperglycemic by alternating exposure to 2% glucose/0% glucose solution every 24hr. Control fish were alternately exposed to either 0% glucose/0% glucose every 24hr or 2% mannitol/0% glucose every 24hr (osmotic control). After 4 and 8 weeks of hyperglycemic conditions, retinas were removed and processed for immunocytochemistry and Western Blot analysis to determine changes in neurotransmitter distribution and content. For immunocytochemistry, retinal cryostat sections were probed with antibodies to GABA, TOH, glutamate, and GFAP; secondary antibodies were conjugated to TRITC or Cy-3. Labeled cryostat sections were viewed to determine changes in the distribution of these neurochemicals. Western Blots were used to quantify changes in these compounds.
Results: :
After 4 weeks, no changes were observed in GFAP levels, but after 8 weeks GFAP levels appear to increase. Glutamate labeling also appears to increase during this time. In contrast, TOH levels appear to decrease; while GABA labeling does not appear different from controls.
Conclusions: :
After 2 months of hyperglycemic conditions, increased glutamate immunoreactivity and increased GFAP levels, but decreased TOH immunoreactivity were observed. These findings are consistent with neurochemical changes previously reported following hyperglycemia in diabetic models suggesting zebrafish is a potential new model in which to study diabetic retinopathy.
Keywords: diabetic retinopathy • neurotransmitters/neurotransmitter systems