Localization and seizure-regulation of integrin β1 mRNA in adult rat brain
Recent findings indicate that RGD-binding integrin receptors play a critical role in the maintenance of long-term potentiation but the identity and location of the integrin proteins involved are not known. The integrin beta1 is of particular interest in regard to synaptic plasticity because it is a component of many of the RGD-binding integrins and beta1-immunoreactivity has been localized within synaptic density fractions. The present study used in situ hybridization to evaluate the distribution of beta1 mRNA in adult rat brain and to determine if expression is altered by seizures. In untreated rats, beta1 mRNA is present at high levels in the ventricular epithelium and discrete neuronal groups including the magnocellular hypothalamic and efferent cranial nerve nuclei and the cerebellar Purkinje cells. Hybridization was less dense in the substantia nigra and hippocampal stratum pyramidale and low but present throughout the gray matter. Limbic seizures increased beta1 cRNA labeling of both neurons (e.g., hippocampal stratum pyramidale) and astroglial cells from 8 h through 48 h after seizure onset. These results indicate that in adult rat brain, beta1 mRNA is expressed by both neurons and glia; neuronal expression is highest in hypothalamic and peripherally projecting neurons capable of substantial morphological plasticity. Seizure effects demonstrate that beta1 is positively regulated by activity, and suggest that activity-dependent expression may play a role in synaptic plasticity in the adult brain.