ST B AND DBA/2 MICE DIFFER IN BRAIN ALPHA-BUNGAROTOXIN BINDING AND ALPHA-7 NICOTINIC RECEPTOR SUBUNIT MESSENGER-RNA LEVELS - A QUANTITATIVEAUTORADIOGRAPHIC ANALYSIS/

Inbred mouse strains vary in sensitivity to a number of behavioral and physiological effects produced by nicotine. Differences in sensitivit y to nicotine are correlated with variance in the number of brain nico tinic receptors as measured in regionally dissected brain tissue. The studies reported here used quantitative autoradiography and in-situ hy bridization methods to measure regional levels of alpha-bungarotoxin ( alpha BTX) binding and alpha 7 mRNA levels. Two inbred mouse strains, ST/b and DBA/2, were compared because these strains differ maximally i n sensitivity to nicotine-induced seizures and in alpha BTX binding me asured in regional brain homogenates. The binding of alpha BTX was sig nificantly 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 alpha 7 mRNA levels were also detected, but these were not as wides pread as were the alpha BTX binding differences. The alpha 7 mRNA leve ls were significantly correlated with alpha BTX binding in both mouse strains which suggests that the strain differences in binding are rela ted, in part, to the levels of alpha 7 mRNA.