Acute pentylenetetrazol injection reduces rat GABAA receptor mRNA levels and GABA stimulation of benzodiazepine binding with no effect on benzodiazepine binding site density

The effects of a single convulsive dose of pentylenetetrazol (PTZ, 45 mg/kg i.p.) on rat brain g-aminobutyric acid type A (GABAA) receptors were studied. Selected GABAA receptor subunit mRNAs were measured by Northern blot analysis (with b-actin mRNA as a standard). Four hours after PTZ, the GABAA receptor g2-mRNA was decreased in hippocampus, cerebral cortex, and cerebellum; a1-mRNA was decreased in cerebel-lum; and b2 subunit mRNA was decreased in cortex and cer-ebellum. The a5 subunit mRNA level was not altered. Those mRNAs that had been reduced were increased in some brain regions at the 24-h time point, and these changes reverted to control levels by 48 h. PTZ effect on GABAA receptors was also studied by autoradiographic binding assay with the benzodiaz-epine agonist [3H]flunitrazepam (FNP), the GABAA agonis