Prepulse inhibition (PPI) is the reduction in the startle response caused by a low intensity non-startling stimulus (prepulse) which is presented shortly before the startle stimulus and is an operational measure of sensorimotor gating. PPI is impaired in schizophrenia patients and in rats with central dopamine (DA) activation. The inferior colliculus (IC) is a critical part of the auditory pathway mediating acoustic PPI. The activation of the IC by the acoustic prepulse reduces startle magnitude. The aim of this study was to elucidate the role of DA transmission of the IC on the development of acoustic PPI. Bilateral microinjections of apomorphine (9.0 μg/0.5 μL), an agonist of D(2) receptors, into the IC disrupted PPI while microinjections of haloperidol (0.5 μg/0.5 μL), an antagonist of D(2) receptors, into this structure did not alter PPI. These results suggest that dopamine-mediated mechanisms of the IC are involved in the expression of PPI in rodents.
The present study evaluated the effects of postnatal intermittent hypoxia on locomotor activity and neuronal cell survival in early adulthood rats. During a critical period of brain development on postnatal day (PD) 7-11, male rat pups were exposed to intermittent hypoxia and randomly assigned to three experimental groups: (1) intermittent hypoxia, (2) normoxia, and (3) control (unhandled). One and a half months later on PD56, a behavioral test was conducted, and cell survival was estimated in the hilus, dental gyrus, and CA1 and CA3 subfields of the hippocampus, nucleus accumbens shell and core, dorsal and ventral striatum, and prefrontal cortex. Our results showed that intermittent hypoxia produced hyperactivity that correlated well with psychomotor agitation observed in patients with schizophrenia. Moreover, post-hypoxic rats exhibited a reduction of the number of neurons in the hilar region of the hippocampusanddorsalstriatum,structuresthathavebeenneuropathologicallyassociatedwithschizophrenia.Thesefindingssuggest that intermittent hypoxia can modify the pattern of locomotor activity and selectively affect neurons in rats tested in early adulthood.
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