HIPPOCAMPAL VOLUME AND NEURONAL NUMBER IN TS65DN MICE - A MURINE MODEL OF DOWN-SYNDROME

Ts65Dn mouse displays a partial triplication of chromosome 16 and is a dopted as a model for Down syndrome (DS). It is known that Ts65Dn mice present memory deficiencies. In order to gain insight into the cause of these deficiencies, we studied the possibility of changes in volume s and neuronal numbers in different regions of the hippocampus (dentat e gyrus, CA3, CA2 and CA1) in trisomic mice as compared to control lit termates using stereological methods. The mean hippocampal volumes of Ts65Dn mice did not show significant differences as compared to contro ls, except in CA2 where there was a barely significant decrease. Howev er, mean neuron number was significantly lower in Ts65Dn mice than in controls in dentate gyrus (43.7 x 10(4), CV 21%, n = 5, vs. 30.4 x 10( 4), CV 18.1%, n = 4) and higher in CA3 (23.1 x 10(4), CV 18.9% vs. 33. 3 x 10(4), CV 14.9%). These quantitative changes may account for the m emory deficiencies observed in Ts65Dn mice. (C) 1998 Elsevier Science Ireland Ctd. AIl rights reserved.