Pharamacological modulation of GABA, glutamate, and acetylcholine receptor-mediated neurotransmission holds promise for the development of novel medication strategies for mental retardation: overview and hypotheses / Stephen I. Deutsch, Richard B. Rosse, Barbara L. Schwartz -- Co-occurrence of MR and other conditions: searching for cause: consideration of the co-occurrence of mental retardation and other conditions / Laura L. Jelliffe-Pawlowski -- Genomic imprinting and mental retardation: Angelman and Prader-Willi syndromes / AK Thomson, EJ Glasson, AH Bittles -- Molecular mechanisms of mental retardation in Down syndrome / Mohammed Rachidi, Carmela Lopes -- Down syndrome and immunity / Diego Franciotta, Annapia Verri, Luigi Nespoli -- New insights into X-linked mental retardation: from clinical to molecular approaches / CB Santos-Reboucas, MMG Pimentel -- Cardiac dysautonomia and mental retardation / Maurizio Acampa, Francesca Guideri