Neonatal ventral hippocampal lesions modify pain perception and evoked potentials in rats

This work concerns the debate surrounding the modified pain reactivity of patients with schizophrenia and other possible perceptive distortions. Rats with a neonatal ventral hippocampal lesion (NVHL) were used to model the neuro-developmental aspect of schizophrenia, and their reactivity to various stimuli was evaluated. The results could also help understand sensory deficits in other neuro-developmental disorders. Behavioural reactions to graduated painful thermal and mechanical stimuli were observed, and evoked potential responsiveness to tactile, visual and acoustic non-painful stimuli was recorded and compared to non-operated and sham lesioned controls. A higher threshold was observed with painful mechanical stimuli and shorter paw withdrawal latency with thermal stimuli. This was particularly relevant as there was no change in the evoked potentials triggered by non-nociceptive tactile stimulation of the same part of the body. There was a 10 dB(A) increase in the auditory threshold and a suppression of auditory sensory motor gating. Visually evoked potentials did not appear to be affected. Taken together, the results showed that NVHL-evoked alteration of brain development induces mechanical hypoalgesia, thermal hyperalgesia and auditory sensory changes. The data also contribute towards elucidating mechanisms underlying sensory deficits in neurodevelopmental diseases, including schizophrenia.