Homogenous glycine receptor expression in cortical plate neurons and cajal-retzius cells of neonatal rat cerebral cortex

• Published in: Neuroscience 2004, Vol.123 (3), p.715-724
• Main Authors: Okabe, A, Kilb, W, Shimizu-Okabe, C, Hanganu, I.L, Fukuda, A, Luhmann, H.J
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Biological and medical sciences; Cerebral Cortex - cytology; Cerebral Cortex - drug effects; Cerebral Cortex - metabolism; cortical development; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists - pharmacology; Fundamental and applied biological sciences. Psychology; GABA Antagonists - pharmacology; Gene Expression Regulation, Developmental - physiology; Male; marginal zone; Membrane Potentials - drug effects; Membrane Potentials - physiology; Neurons - cytology; Neurons - drug effects; Neurons - metabolism; picrotoxin; Rats; Rats, Wistar; Receptors, Glycine - biosynthesis; Receptors, Glycine - genetics; single-cell multiplex RT-PCR; strychnine; Vertebrates: nervous system and sense organs; whole-cell patch-clamp
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2003.10.014

Glycinergic membrane responses have been described in cortical plate neurons (CPn) and Cajal-Retzius cells (CRc) during early neocortical development. In order to elucidate the functional properties and molecular identity of glycine receptors in these two neuronal cell types, we performed whole-cell patch-clamp recordings and subsequent single-cell multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) analyses on visually identified neurons in tangential and coronal slices as well as in situ hybridizations of coronal slices from neonatal rat cerebral cortex (postnatal days 0–4). In both CPn and CRc the glycinergic agonists glycine, β-alanine and taurine induced inward currents with larger current densities in CRc. The functional properties of these currents were similar between CPn and CRc. In both cell types the glycine receptor showed a higher affinity for glycine than for the glycinergic agonists β-alanine and taurine. The glycinergic responses of both cells were blocked by the glycinergic antagonist strychnine and were unaffected by the GABAergic antagonist bicuculline (100 μM), the N-methyl- d-aspartic acid receptor antagonist (±)-2-amino-5-phosphonopentatonic acid (60 μM) and by picrotoxin (30 μM), an antagonist of α homomeric glycine receptors. Single-cell multiplex RT-PCR revealed the expression of glycine receptor α 2 and β subunits in CPn and CRc, while no α 1 and α 3 subunits were observed. In situ hybridization histochemistry showed the expression of mRNAs for α 2 and β subunits within the cortical plate and in large neurons of the marginal zone, while there were no signals for α 1 and α 3 subunits. In summary, these results suggest that CPn and CRc express glycine receptors with similar functional and pharmacological properties. The correlation of pharmacological properties and mRNA expression suggests that the glycine receptors in both cell types may consist of α 2/β heteromeric receptors.