Alterations in hippocampal excitability, synaptic transmission and synaptic plasticity in a neurodevelopmental model of schizophrenia

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Abstract

The risk of developing schizophrenia has been linked to perturbations in embryonic development, but the physiological alterations that result from such insults are incompletely understood. Here, we have investigated aspects of hippocampal physiology in a proposed neurodevelopmental model of schizophrenia, induced during gestation in rats by injection of the antimitotic agent methylazoxymethanol acetate (MAM) at embryonic day 17 (MAME17). We observed a reduction in synaptic innervation and synaptic transmission in the dorsal hippocampus of MAME17 treated rats, accompanied by a pronounced increase in CA1 pyramidal neuron excitability. Pharmacological investigations suggested that a deficit in GABAergic inhibition could account for the increase in excitability; furthermore, some aspects of the hyper-excitability could be normalised by the GABAA receptor (GABAAR) potentiator diazepam. Despite these alterations, two major forms of synaptic plasticity, long-term potentiation (LTP) and long-term depression (LTD) could be readily induced. In contrast, there was a substantial deficit in the reversal of LTP, depotentiation. These findings suggest that delivering neurodevelopmental insults at E17 may offer insights into some of the physiological alterations that underlie behavioural and cognitive symptoms observed in schizophrenia.

This article is part of a Special Issue entitled ‘Schizophrenia’.

Highlights

▸ Neurodevelopmental disruption at E17 results in specific alterations in hippocampal physiology in rats. ▸ Hippocampal synaptic transmission is decreased. ▸ Hippocampal excitability is increased due to a deficit in inhibition. ▸ Long-term potentiation and long-term depression can be induced, however there is a specific deficit in depotentiation. ▸ This pattern of deficits may underlie abnormal behaviours in this model of schizophrenia.

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