Genotypic variation in striatal calmodulin content

Abstract

CBA/J and BALB/cJ mice have quantitative differences in the nigrostriatal projection. The number of nigral tyrosine hydroxylase reactive neurons, nigral and striatal tyrosine hydroxylase activity and the density of striatal D-2 dopamine receptors are all less in the CBA/J compared to the BALB/cJ mouse. An unrelated strain, the C57BL/6J, has a striatal D-2 dopamine receptor density that is intermediate to that of CBA/J and BALB/cJ mice. CBA/J mice also show deficits in the ability of brain monoaminergic receptor systems to develop supersensitivity. Calmodulin may participate in several striatal dopaminergic receptor mechanisms. Thus, striatal calmodulin was examined in CBA/J, C57BL/6J and BALB/cJ mice. Striatal calmodulin was greater in CBA/J mice than in C57BL/6J or BALB/cJ. In all three strains, cerebral cortical calmodulin was similar. The percent distribution of total striatal calmodulin between soluble and particulate fractions was similar in the three strains. Calcium redistributed soluble striatal calmodulin into the particulate fraction and EGTA shifted calmodulin from the particulate into the soluble fraction. The percent of total striatal calmodulin redistributed by either treatment was similar in all three strains. Gel filtration chromatography of heat-treated soluble extracts from CBA/J and BALB/cJ striatum was similar in elution pattern, although more calmodulin was observed in extracts from the CBA/J. Possible mechanisms for the strain differences in calmodulin are discussed along with their relationship to strain differences in striatal dopamine receptor subtypes.