Differential effects of histamine on the N-methyl-d-aspartate channel in hippocampal slices and cultures
| Autor: | J.M. Bekkers, S. Ymer, Maria Vidovic |
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| Rok vydání: | 1996 |
| Předmět: |
HEPES
Dose-Response Relationship Drug General Neuroscience Glutamate receptor Biology Hippocampal formation Hippocampus Receptors N-Methyl-D-Aspartate Rats chemistry.chemical_compound EGTA Slice preparation chemistry Excitatory postsynaptic potential Biophysics Animals NMDA receptor Rats Wistar Neuroscience Cells Cultured Histamine |
| Zdroj: | Neuroscience. 72:669-677 |
| ISSN: | 0306-4522 |
| DOI: | 10.1016/0306-4522(95)00586-2 |
| Popis: | The effect of histamine on N -methyl- d -aspartate currents was investigated in pyramidal neurons in the CAI region of acute hippocampal slices from juvenile rats. The objective was to compare histamine effects in the slice with those previously reported in acutely dissociated and cultured hippocampal neurons. Micromolar concentrations of histamine had no effect on N -methyl- d -aspartate-mediated excitatory postsynaptic currents in the slice, in contrast to the large enhancement seen in culture under identical conditions. However, millimolar concentrations of histamine blocked these currents both in the slice and in culture. Possible reasons for the lack of enhancement in the slice were explored as follows. (1) Histamine could not penetrate the slice or was already present at high concentrations inside the slice. This was tested by recording N -methyl- d -aspartate currents elicited in outside-out patches pulled from the somas of CAI slice neurons. Histamine still had no effect in patches, whereas the corresponding experiment for cultured neurons showed robust enhancement. (2) Slices release an endogenous ligand that binds with high affinity to the histamine site on the N -methyl- d -aspartate receptor, blocking its activation. This was tested by superfusing cultures with supernatant from homogenized slice tissue. Histamine enhancement was maintained in these cultures. (3) CAI slices and cultures express different N -methyl- d -aspartate receptor subtypes. The reverse transcription-polymerase chain reaction technique was used to examine the expression of messenger RNA encoding N -methyl- d -aspartate receptor subunits in the two systems. No difference was found in the whole-tissue expression of messenger RNA for the NR2A, 2B or 2C subunits or for the eight known splice variants of the NRI subunit. It is hypothesized that the differential enhancing effect of histamine in slices and culture involves posttranslational modifications or other factors that modulate the N -methyl- d -aspartate receptor/ion channel according to its environment. |
| Databáze: | OpenAIRE |
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