Histidine-decarboxylase knockout mice show deficient nonreinforced episodic object memory, improved negatively reinforced water-maze performance, and increased neo- and ventro-striatal dopamine turnover.

@article{Dere2003HistidinedecarboxylaseKM,
  title={Histidine-decarboxylase knockout mice show deficient nonreinforced episodic object memory, improved negatively reinforced water-maze performance, and increased neo- and ventro-striatal dopamine turnover.},
  author={E. G{\"o}zde Dere and Maria A De Souza-Silva and Bianca Topic and Richard E. Spieler and Helmut L. Haas and Joseph P. Huston},
  journal={Learning & memory},
  year={2003},
  volume={10 6},
  pages={510-9}
}
The brain's histaminergic system has been implicated in hippocampal synaptic plasticity, learning, and memory, as well as brain reward and reinforcement. Our past pharmacological and lesion studies indicated that the brain's histamine system exerts inhibitory effects on the brain's reinforcement respective reward system reciprocal to mesolimbic dopamine systems, thereby modulating learning and memory performance. Given the close functional relationship between brain reinforcement and memory… CONTINUE READING