This study seeks to continue investigations on genetic mechanisms in the control of central dopaminergic (DA) systems. First, genetic selection experiments will be carried out with mice for high and low number of DA neurons in substantia nigra (Ag cell group). In the selection experiments we wish to determine if: a., there is a common genetic control on the number of DA neurons shared by all DA systems in the brain, b., cellular characteristics of DA systems (such as number of cell bodies and axonal arborization) are affected by identical or separate genetic mechanisms, c., changes in number of DA neurons are correlated with natural and drug-induced behaviors mediated by DA neurons. The established lines can be used as models for disorders where comparable deviations in DA systems are involved (e.g. Parkinson's disease). Second, we wish to study if there are major gene effects on brain DA systems. Third, the selected lines will be studied to determine if genetic differences in the tuberohypophyseal DA systems are correlated with size and neuronal number in pars intermedia of hypophysis, Beta-Endorphin, and Alpha-MSH secretion, and behavioral processes effected by these hormones.
