ADX—No receptor occupation | LO-CORT—MR activation | HI-CORT—MR + GR activation | |
---|---|---|---|
Voltage-gated Ca channel mRNAs (α1 subunits) | |||
P/Q-type | ↑ | ↓ | ↑ |
N-type | ↔ | ↔ | ↔ |
L-type | ↑ | ↓ | ↑ |
AMPA receptor subunit mRNAs | |||
GluR-1 | ↔ | ↔ | ↔ |
GluR-2 | ↓ | ↑ | ↓ |
GluR-3 | ↔ | ↔ | ↔ |
GluR1:GluR2 | ↓ | ↑ | ↓ |
NMDA receptor subunit mRNAs | |||
NR1 | ↔ | ↔ | |
NR2A | ↔ | ↑ | ↔ |
NR2B | ↑ | ↓ | ↑ |
NR2C | ↔ | ↔ | ↔ |
NR2A:NR2B | ↓ | ↑ | ↓ |
Potential biological consequences on Ca conductance in Ca1 neurons | ↑ Ca-influx | ↓ Ca-influx | ↑ Ca-influx |
When MRs and GRs are unoccupied, or both are occupied, dissociated CA1 pyramidal neurons express relatively high levels of P-(α1A) and L-(α1C/D) type Ca channel mRNAs, a higher ratio of GluR-1 to GluR-2 mRNA, and a lower ratio of NR2A to NR2B mRNA. Parallel changes in levels of functional protein may lead to enhanced Ca influx, which if continuously present over the long term, may compromise neuronal integrity. When MRs are solely occupied, dissociated CA1 neurons express relatively low levels of P- and L-type Ca channel mRNAs, a lower ratio of GluR-1 to GluR-2 mRNA, and a higher ratio of NR2A to NR2B mRNA. Concomitant alterations in levels of functional protein may act to limit Ca influx, contributing to the previously observed neuroprotective effect of MR occupation.