Heterozygous reeler mice exhibit alterations in sensorimotor gating but not presynaptic proteins

Post mortem, reduced brain reelin is noted in schizophrenia. Accordingly, the reelin-haploinsufficient heterozygous reeler mouse (HRM) has been posited as a murine model of the illness. One study reported that HRM exhibit deficits in prepulse inhibition (PPI) of the acoustic startle reflex, a sensorimotor-gating behavior that is disrupted in schizophrenia, although this finding has not been reproduced. To extend the characterization of putative sensorimotor-gating deficits in HRM, these mice were subjected to a sophisticated series of PPI tests. Mice were tested in a cross-modal PPI protocol that combined an acoustic prepulse with a tactile startle stimulus and also in a protocol that included varying prepulse-pulse intervals and varying acoustic startle pulse intensities. Levels of acoustic startle habituation and cross-modal PPI were significantly lower in HRM, although unimodal PPI did not differ. The HRM also exhibited increased PPI compared to wildtypes at short interstimulus intervals between prepulse and pulse stimuli when the interval between the acoustic prepulse and pulse were varied, and were more reactive to higher intensity startle stimuli. Some of these deficits in sensorimotor gating parallel those of schizophrenia, a disease characterized by alterations in synaptic protein expression. Therefore, levels of presynaptic proteins were measured in multiple brain regions using ELISA in HRM. No significant alterations in presynaptic protein expression were found. Thus, HRM exhibit a complex pattern of changes in startle reactivity and sensorimotor gating, with both similarities to and differences from schizophrenia. However, it is unlikely that these behavioral differences may be accounted for by altered regional levels of presynaptic proteins.