Role of hippocampal Met-enkephalin in the genotype-dependent regulation of exploratory behavior in mice.

Intrahippocampal microinjections with anti-Met-enkephalin antiserum enhanced novelty-induced vertically oriented exploratory acts and horizontal locomotor activity in inbred mouse strain DBA/2 and reduced these behaviors in C57BL/6 so that strain differences originally present between the normal serum controls were eliminated after antiserum treatment. These opposite effects suggest that hippocampal Met-enkephalin participates in the genotype-dependent control of mouse exploration.