Glutamate evokes firing through activation of kainate receptors in chick accessory lobe neurons.
Ten pairs of protrusions, called accessory lobes (ALs), exist at the lateral sides of avian lumbosacral spinal cords. Histological and behavioral evidence suggests that neurons are present in ALs and the AL acts as a sensory organ of equilibrium during walking. Neurons in the outer layer of the AL consistently show glutamate-like immunoreactivity and neurons in the central region of the AL show glutamate receptor-like immunoreactivity. However, it is unknown how glutamate acts on the functional activity of AL neurons. In this study, we examined the effects of glutamate on the electrical activities of AL neurons using the patch clamp technique. There are two types of neurons among isolated AL neurons: spontaneously firing and silent neurons. Among silent neurons, 42 % of neurons responded to glutamate and generated repetitive firing. Kainate and glutamate in combination with the NMDA receptor antagonist, MK-801, also induced firing and evoked an inward current. On the other hand, the application of AMPA, NMDA or glutamate in combination with the non-NMDA receptor antagonist, CNQX, did not. These results indicate that chick AL neurons express functional kainate receptors to respond to glutamate and suggest that the glutamatergic transmission plays a role in excitatory regulation of AL neurons of the chick.
The United Graduate School of Veterinary Science, Yamaguchi University, 1677-1, Yoshida, Yamaguchi 753-8515, Japan.
Yuko
Y
Yamanaka
Naoki
N
Kitamura
Hikaru
H
Shinohara
Keita
K
Takahashi
Izumi
I
Shibuya
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D001703:Biophysics; D002478:Cells, Cultured; D002642:Chick Embryo; D004347:Drug Interactions; D004558:Electric Stimulation; D018683:Excitatory Amino Acid Agents / Q000494:pharmacology*; D018698:Glutamic Acid / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D018092:Kainic Acid Receptors / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D018683:Excitatory Amino Acid Agents; D018698:Glutamic Acid; D018092:Kainic Acid Receptors; D005680:gamma-Aminobutyric Acid