AI Article Synopsis
- Gerbils exhibit a significantly higher density of [3H]-PK 11195 binding sites in both cortical and hippocampal membranes when compared to rats, indicating a species-specific difference.
- RO 5-4864, a peripheral-type benzodiazepine, shows lower affinity for [3H]-PK 11195 in gerbils versus rats, while central benzodiazepines also reflect a similar trend in their binding affinities.
- After inducing forebrain ischaemia in Mongolian gerbils, there was a notable decrease in hippocampal 5-HT1A binding sites and a significant increase in [3H]-PK 11195 binding sites, suggesting alterations in receptor density without changing ligand affinity.
Article Abstract
1. A high density of [3H]-PK 11195 binding sites was present in gerbil cortical membranes (Bmax [3H]-PK 11195 1360 +/- 71 fmol mg-1 protein) in comparison to rat cortical membranes (254 +/- 21 fmol mg-1 protein). This effect was species-specific as similar findings were obtained with hippocampal membranes (Bmax 1430 +/- 111 fmol mg-1 protein in gerbil, compared to 196 +/- 31 in rat). 2. RO 5-4864, also a peripheral type benzodiazepine compound, displayed low affinity for the [3H]-PK 11195 site in the gerbil (pKi 6.57 +/- 0.02 and 6.70 +/- 0.12 in hippocampus and cortex respectively) compared to rat (pKi 8.16 +/- 0.07 and 8.48 +/- 0.02). Central benzodiazepine compounds, diazepam and flunitrazepam, also displayed this trend. 3. RO 5-4864 displaced [3H]-PK 11195 binding from gerbil and rat cortical membranes through a competitive interaction with Hill slopes close to unity. In both tissues, saturation isotherms of [3H]-PK 11195 binding indicated that the presence of RO 5-4864 caused changes in Kd without any effect on Bmax. In kinetic experiments, the presence of RO 5-4864 failed to modify the rate of dissociation of [3H]-PK 11195 from equilibrium in both rat and gerbil cortical membranes. 4. Forebrain ischaemia in the Mongolian gerbil (5 min bilateral carotid artery occlusion) with 7 days recovery caused a significant (P<0.05) decrease in the density of hippocampal 5-HTlA binding sites labelled by [3H]-8-OH-DPAT (Bmax control, 393 +/- 33 fmol mg-1 protein; ischaemic, 289 +/- 21 fmol mg protein)and an increase (P<0.01) in [3H]-PK 11195 binding sites (Bmax control, 1430 +/- 111 fmol mg-1 protein; ischaemic, 2160 +/- 170 fmol mg-1 protein). Ischaemia and recovery had no effect on the affinity of either ligand.5. Autoradiography experiments in gerbil brain sections revealed that the ischaemia-induced increase in[3H]-PK 11195 binding was consistent and significant in the CA, subfield on the hippocampus (control,152 +/- 42 fmol mg-1 tissue; ischaemic, 314 +/- 43 fmol mg-1 tissue).
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2175675 | PMC |
| http://dx.doi.org/10.1111/j.1476-5381.1993.tb13588.x | DOI Listing |
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