Social isolation increases the density of [125I]omega-conotoxin GVIA binding sites in the rat frontal cortex and caudate nucleus.

Rats were reared from weaning either in isolation or in social groups for 12 weeks. Potential isolation-related changes in L- and N-type voltage-sensitive calcium channels (VSCCs) were assessed by the in vitro binding of [3H]isradipine (100 pM) and [125I]omega-conotoxin GVIA (4 pM) to membranes prepared from three discrete central nervous system regions: frontal cortex, caudate nucleus and hippocampus. The [3H]isradipine binding was generally not affected by isolation. However, [125I]omega-conotoxin GVIA binding was significantly higher in frontal cortex (52%) and caudate nucleus (75%) of isolated rats when compared with socially reared controls. The increased [125I]omega-conotoxin GVIA binding reflected an elevated density of binding sites without an alteration of receptor affinity. The possible contribution of an increased density of neuronal N-VSCCs (as labeled with [125I]omega-conotoxin GVIA) to the behavioral and neurochemical changes observed in 'isolation syndrome' is discussed.