Brain Adrenoceptor Binding Sites in Mice Susceptible (DBA/2J) and Resistant (C57 Bl/6) to Audiogenic Seizures

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Abstract
We have examined if the age-related susceptibility of DBA/2J mice to audiogenic seizures is the result of an abnormality in the number of sensitivity of brain adrenoceptors. The binding of .alpha.1-, .alpha.2-, and .beta.-adrenoceptor ligands to membranes prepared from whole brain or regions of brain of DBA/2J mice was measured at various ages, corresponding to the periods before, during, and after the maximal sensitivity to audiogenic seizures. For comparison, we have studied concurrently age-matched C57 Bl/6 mice, a strain resistant to audiogenic seizures at all ages. There was no difference in the binding of .alpha.2- or .beta.-adrenoceptor ligands to whole brain membranes between the two strains of mice at any age. The maximal number of .alpha.1-adrenoceptor binding sites was lower in whole brains of DBA/2J mice than of C57 Bl/6 mice at all ages studied except 13-15 days of age. The differences were small (maximally 17%) but were statistically significant at 21-23 days of age, the time of maximal sensitivity of DBA/2J mice to audiogenic seizures. No difference between the two strains was found in the number of affinity of .alpha.1- or .alpha.2-adrenoceptor binding sites at any age in any of the brain regions studied. The age-related susceptibility of DBA/2J mice to audiogenic seizures is not the result of an abnormality in number or sensitivity of .alpha.2- or .beta.-adrenoceptor binding sites, but a reduced number of .alpha.1-adrenoceptor binding sites may be involved.