Glutamate modulates intracellular Ca2+ stores in brain stem auditory neurons

Area of Science:

• Neuroscience
• Cellular Biology
• Auditory System Research

Background:

• Neurons in the avian cochlear nucleus (NM) play a crucial role in auditory processing.
• Intracellular calcium ion concentration ([Ca2+]i) dynamics are vital for neuronal function and survival.
• Glutamate is a key excitatory neurotransmitter in the central nervous system.

Purpose of the Study:

• To investigate the role of glutamate in modulating caffeine-sensitive intracellular calcium stores in NM neurons.
• To determine if glutamate affects the release of calcium from intracellular stores.
• To explore the potential involvement of calcium regulation in glutamate deprivation-induced cell death.

Main Methods:

• Fura-2 imaging was employed to measure changes in [Ca2+]i.
• Experiments were conducted in Ca(2+)-free media to isolate intracellular calcium store dynamics.
• Caffeine was used to stimulate the release of calcium from stores.
• The effects of glutamate and a metabotropic glutamate receptor agonist (ACPD) on caffeine-induced calcium release were assessed.

Main Results:

• Caffeine (100 mM) significantly increased [Ca2+]i by approximately 250 nM in Ca(2+)-free media.
• Glutamate (1 mM) significantly attenuated the caffeine-stimulated rise in [Ca2+]i.
• The metabotropic glutamate receptor agonist, ACPD, also inhibited the caffeine-stimulated increase in [Ca2+]i.
• Glutamate deprivation, induced by cochlear removal, led to an increase in [Ca2+]i, potentially from store release.

Conclusions:

• Glutamate plays a significant role in regulating intracellular calcium stores within NM neurons.
• Glutamate's inhibitory effect on calcium release may protect neurons from excitotoxicity.
• Calcium-induced calcium release (CICR) mechanisms are hypothesized to be involved in cell death following glutamate deprivation.