Neuronal and synaptic plasticity in subregions of rat hippocampus after antidepressant treatment
Abstract
Neuronal plasticity in the hippocampal formation is thought to play an important role in the pathophysiology of depression and effects of antidepressant therapy.
In these studies, we aimed at investigating the underlying effect of antidepressants on the neuronal plasticity in the hippocampus in normal Sprague Dawley (SD) rats and in an animal model of depression (Flinders Sensitive Line rats (FSL). Design-based stereological methods were used to quantify regional volumes and the number of neurons and synapses.
First, in SD rats, we found that following treatment during 14 days with imipramine that the number and percentage of spine synapses increased significantly and, conversely, the percentage of shaft synapses significantly decreased.
Second, in SD rats, the, volumes of granule cell layer (GCL) and Hilus of the hippocampus were significantly larger following chronic treatment with Electro Convulsive Seizures (ECS). The neuron number in GCL and synapse number in CA1 were significantly increased in the ECS treatment group.
Third, using FSL rats we observed that the volume, neuron number, and synapse number were significantly smaller in the naïve FSL rats versus their controls (FRL), and were related to decreased immobility in the forced swim test. Moreover, the neuron numbers in GCL and spine synapse numbers in CA1 was significantly increased following imipramine treatment and, conversely, the shaft synapse numbers significantly decreased in the imipramine treated FSL rats.
Our findings provide experimental evidence for supporting the recent theories that major depression may be related to impairments of structural plasticity and neural cellular resilience, and that antidepressants counteract the structural impairments.Â
In these studies, we aimed at investigating the underlying effect of antidepressants on the neuronal plasticity in the hippocampus in normal Sprague Dawley (SD) rats and in an animal model of depression (Flinders Sensitive Line rats (FSL). Design-based stereological methods were used to quantify regional volumes and the number of neurons and synapses.
First, in SD rats, we found that following treatment during 14 days with imipramine that the number and percentage of spine synapses increased significantly and, conversely, the percentage of shaft synapses significantly decreased.
Second, in SD rats, the, volumes of granule cell layer (GCL) and Hilus of the hippocampus were significantly larger following chronic treatment with Electro Convulsive Seizures (ECS). The neuron number in GCL and synapse number in CA1 were significantly increased in the ECS treatment group.
Third, using FSL rats we observed that the volume, neuron number, and synapse number were significantly smaller in the naïve FSL rats versus their controls (FRL), and were related to decreased immobility in the forced swim test. Moreover, the neuron numbers in GCL and spine synapse numbers in CA1 was significantly increased following imipramine treatment and, conversely, the shaft synapse numbers significantly decreased in the imipramine treated FSL rats.
Our findings provide experimental evidence for supporting the recent theories that major depression may be related to impairments of structural plasticity and neural cellular resilience, and that antidepressants counteract the structural impairments.Â
ISSN 1903-7236