ST/b and DBA/2 mice differ in brain α-bungarotoxin binding and α7 nicotinic receptor subunit mRNA levels: A quantitative autoradiographic analysis

Inbred mouse strains vary in sensitivity to a number of behavioral and physiological effects produced by nicotine. Differences in sensitivity to nicotine are correlated with variance in the number of brain nicotinic receptors as measured in regionally dissected brain tissue. The studies reported here used quantitative autoradiography and in-situ hybridization methods to measure regional levels of α-bungarotoxin (αBTX) binding and α7 mRNA levels. Two inbred mouse strains, ST/b and DBA/2, were compared because these strains differ maximally in sensitivity to nicotine-induced seizures and in αBTX binding measured in regional brain homogenates. The binding of αBTX was significantly greater in the St/b strain in 42 of 127 brain regions that were analyzed, and a trend towards increased binding was seen in many additional brain regions. The most consistent strain differences were found in hippocampal, thalamic and pontine nuclei. Strain differences in α7 mRNA levels were also detected, but these were not as widespread as were the αBTX binding differences. The α7 mRNA levels were significantly correlated with αBTX binding in both mouse strains which suggests that the strain differences in binding are related, in part, to the levels of α7 mRNA.