Glutamate Receptors in Both Brain and Eyes

Allison Shelley

February 24, 2012

February 24, 2012 — Glutamate receptors exist not only in the brain but also in the eyes, report researchers. This may explain the link between neurological diseases and cataracts and may also play a role in the unintended consequences antidepressants and antiepileptic drugs have.

Dr. Peter Frederikse

"It's not intuitive to think the most prevalent receptor for the major neurotransmitter in the brain is also present in the lens," senior investigator Peter Frederikse, PhD, from the University of Medicine and Dentistry in Newark, New Jersey, told Medscape Medical News.

These glutamate receptor proteins and a pivotal GluA2 subunit are expressed in the lens and appear to be regulated in a similar manner to the way they are in the brain, this preclinical work shows. Although the findings are preliminary, Dr. Frederikse says this represents the first hint of an association.

The research was published online January 10 and in the February 10 issue of Biochemical and Biophysical Research Communications.

In this animal study, investigators assessed mouse and rat tissues according to National Institutes of Health guidelines.

"Recent studies identified associations between increased cataracts and epilepsy, and showed increased cataract prevalence with use of antiepileptic drugs as well as some common antidepressants," Dr. Frederikse said.

In the nervous system, glutamate and GluA receptor proteins underlie memory formation and mood regulation and are important in epilepsy. These receptor proteins are also targets for a number of antidepressants and antiepileptic drugs.

Gamma-Aminobutyric Acid Also Implicated

The findings appear consistent with gamma-aminobutyric acid (GABA) receptors and related enzymes expressed in the lens. GABA is the major inhibitory neurotransmitter and is also linked to neural development and plasticity.

These observations suggest that glutamate and GABA have corresponding antagonistic roles in the lens that are associated with the precise cell growth needed to form an optically useful organ in proper alignment with the cornea and retina, the authors explain.

"Our goal now is to use this information to parse out the potential effects of antiepileptics and antidepressants on these off-target sites in the lens," Dr. Frederikse said, "and to determine the role glutamate receptors have in lens biology and pathology."

This study was funded by the National Eye Institute. Dr. Frederikse and 2 coauthors have obtained patent protection related to the current study.

Biophys Res Commun. 2012;418:273-277. Abstract

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