Prenatal development of NMDA receptor composition and function in trigeminal neurons

Area of Science:

• Neuroscience
• Developmental Biology
• Neuropharmacology

Background:

• Prenatal development of neural circuits for feeding behaviors is vital for newborn mammal survival.
• The N-methyl-D-aspartate (NMDA) receptor is known to be critical for postnatal oral-motor functions.

Purpose of the Study:

• To investigate the role of the NMDA receptor in the prenatal development of sucking behavior.
• To examine the developmental changes in NMDA receptor subunits within key brainstem circuits.

Main Methods:

• Physiological experiments using in vitro preparations of fetal rat brainstem to record trigeminal motor outputs and assess NMDA receptor dose response.
• Immunohistochemical studies using antibodies against NMDA receptor subunits (NR1, NR2A, NR2B, NR3A, NR3B) in trigeminal motoneurons (Mo5) and mesencephalic trigeminal neurons (Me5) at different embryonic stages (E17-E21).

Main Results:

• High NMDA agonist concentrations altered the cycle duration of rhythmical trigeminal activity (RTA) in fetal rats.
• In Mo5, NR1, NR2A, NR2B, and NR3A were present, with a decrease in NR2B and an increased NR2A/NR2B ratio from E17 to E20.
• In Me5, NR1, NR2A, and NR3A were present, with decreases in NR2A and NR3A between E17 and E20.

Conclusions:

• The NMDA receptor plays a significant role in the prenatal development and function of oral-motor circuits.
• Observed changes in NMDA receptor subunit expression timing coincide with the prenatal emergence of rhythmical jaw movements and RTA.