Dual effect of glycine on isolated rat suprachiasmatic neurons.
Pharmacological properties of strychnine-sensitive and -insensitive glycine receptors have been investigated in rat suprachiasmatic nucleus (SCN) neurons. Because the SCN neurons were too small for stable intracellular recordings by the glass-microelectrode technique, a conventional whole cell mode patch-clamp technique was employed on the acutely dissociated SCN neurons. Dissociated SCN neurons were morphologically heterogeneous and could be distinguished into several types. All cells responded to glycine in a concentration-dependent manner. The glycine-induced current was primarily Cl- sensitive and competitively blocked by strychnine. The SCN neurons also responded to excitatory amino acids: glutamate, quisqualate, kainate, and N-methyl-D-aspartate (NMDA). Responses to glutamate and aspartate, which are endogenous neurotransmitter candidates, were enhanced by adding glycine. Glycine especially augmented the maximum response to NMDA in a full concentration range. 6-Cyano-7-nitroquinoxaline-2,3-dione (CNQX) did not suppress the strychnine-sensitive glycine response but did suppress the strychnine-insensitive NMDA response in a competitive manner for glycine. The results suggest that glycine influences neural activity in the SCN as a classical inhibitory neurotransmitter and an excitatory neuromodulator.
Ito
C
C
Department of Neurophysiology, Tohoku University School of Medicine, Sendai, Japan.
Wakamori
M
M
Akaike
N
N
D000818:Animals; D004594:Electrophysiology / Q000379:methods; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D005998:Glycine / Q000494:pharmacology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D016318:Quisqualic Acid / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013331:Strychnine / Q000494:pharmacology; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000502:physiology*
D005971:Glutamates; D018698:Glutamic Acid; D016202:N-Methylaspartate; D016318:Quisqualic Acid; D013331:Strychnine; D005998:Glycine