Long-term decrease in the hippocampal [3H]inositoltriphosphate binding following repeated electroshock in the rat

Treatment of trauma with lithium to forestall the development of posttraumatic stress disorder by pharmacological induction of a mild transient amnesia

Posttraumatic stress disorder (PTSD) is a severe anxiety disorder that develops after exposure to trauma. Symptoms include persistent reexperiencing, persistent avoidance, persistent numbing, and persistent hyperarousal. Subsequent to trauma exposure, the onset of symptoms of an acute stress reaction can typically develop over varying amounts of time from days to months. Current pharmacotherapies for PTSD are available after symptoms manifest, and primarily consist of selective serotonin reuptake inhibitor (SSRI) antidepressants. There are currently no FDA approved pharmacological interventions available for the treatment of acutely traumatized individuals to forestall the development of PTSD after trauma and prior to the onset of symptoms. A prominent model of PTSD developed by Roger Pitman attributes the pathogenesis of PTSD to over-consolidated traumatic memories that are mediated by endogenous stress hormones released with trauma and after trauma. The molecular processes of memory consolidation in neurons are mediated by intracellular signaling pathways. One secondary messenger signaling pathway with a putative role in long-term potentiation (LTP) is the inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) secondary messenger system. Lithium, a treatment for bipolar disorder, and a pharmacotherapy that is associated with inducing transient impairments in cognition, memory, and learning, is an inhibitor of inositol monophosphatase (IMP), an enzyme in the IP3 and DAG secondary messenger pathway. I am advancing the hypothesis that the administration of lithium for a brief interval to traumatized individuals at risk for PTSD within the time period after trauma and prior to the onset of symptoms could potentially forestall the development of PTSD by disrupting LTP. I am proposing that this treatment will reduce the incidence of PTSD and reduce the severity of symptoms in those who eventually develop PTSD.

Electroconvulsive stimulations prevent stress-induced morphological changes in the hippocampus

Stress can precipitate major depression and other disorders linked to hippocampal shrinkage. It is hypothesized but not established that treatment of these disorders reverses and prevents the hippocampal changes. Dendritic retraction of individual neurons might in concert with other pathophysiological events contribute to the shrinkage phenomenon. Animal studies have shown that various stress paradigms can induce dendritic retraction in the CA3 pyramidal neurons of the hippocampus. Since electroconvulsive treatment is the most effective treatment in humans with major depression, we investigated whether repeated electroconvulsive stimulations (ECSs) could influence such changes in stressed rats. Furthermore, we investigated whether ECSs per se could influence neuronal branching and total length of the CA3 hippocampal neuronal dendritic tree in normal rats. Rats were stressed using the 21-day 6 h daily restraint stress paradigm. The study shows that stress caused remodelling of the pyramidal neurons by significantly reducing the number of dendritic branch points and total length of the apical dendritic tree. Concomitant administration of ECSs prevented these effects. ECSs had no effect on pyramidal neuron dendrites in normal rats.

Repeated electroconvulsive stimulation impairs long-term depression in the neostriatum

BACKGROUND

Increasing and consistent findings of structural and functional abnormalities in patients with mood disorders demonstrate a clear involvement of the neostriatum. Therefore, the beneficial effect of electroconvulsive stimulation (ECS) treatment of acute state of mood disorder may relate to changes in striatal synaptic plasticity.

METHODS

We studied the effect of ECS treatment on the reported long-term depression (LTD) of synaptic excitatory afferents to striatal medium spiny neurons. Stimulation of the white matter between the cortex and the striatum elicited excitatory postsynaptic potentials (EPSPs) in medium spiny neurons in rat corticostriatal slices while recording using the whole-cell patch-clamp technique.

RESULTS

The EPSPs evoked in striatal neurons undergo LTD with repeated stimulation trains, and LTD of this pathway is impaired in rats after ECS treatment for 1 week, similar to what is reported in chronic lithium treatment. Electroconvulsive stimulation did not affect intrinsic membrane properties or the occurrence of spontaneous EPSCs. Dose-dependent inhibition of the EPSPs by a nonselective agonist of metabotropic glutamate receptor did not change in rats after ECS treatment.

CONCLUSIONS

Our data suggest that the effectiveness of electroconvulsive therapy in mood disorders may be a consequence of LTD impairment of excitatory cortical afferents to striatal projecting neurons.

Mechanism underlying the therapeutic effects of electroconvulsive therapy (ECT) on depression

Electroconvulsive therapy (ECT) is used to treat drug-resistant depressive disorders. The results of studies on the mechanism underlying the effectiveness of ECT on depression are still controversial. ECT stimulus is usually larger than the threshold of induction of seizures and activation of whole-brain is believed to be necessary to produce therapeutic effects. A single ECT session induces alterations of the electroencephalogram (EEG) including initial epileptic discharges, then slow waves, and finally flattened EEG. Repeated ECT results in an increasing number of slower waves in the EEG for as long as a month. ECT-induced changes in various neurotransmitter systems have also been reported. Serotonin (5-hydroxytryptamine, 5-HT) is one of the most important neurotransmitters involved in depressive illness, and ECT alters several 5-HT-receptor subtypes in the central nervous system. 5-HT1A receptors in post-synaptic neurons are sensitized by repeated ECT, but those in pre-synaptic neurons (auto-receptors) are not changed. In addition, our electrophysiological studies have shown that ECT increases sensitivity to 5-HT of 5-HT3 receptors in the hippocampus, resulting in an increase in release of neurotransmitters such as glutamate and gamma-aminobutyric acid. In contrast, ECT decreases the auto-receptor functions in noradrenergic and dopaminergic neurons in the locus coeruleus and substantia nigra, respectively, resulting in an increase in release of noradrenaline and dopamine. In conclusion, 5-HT1A-receptor sensitization may be important for explaining the effectiveness of ECT, as this change induces a decrease in the number of 5-HT2A receptors that are elevated in depressive patients. Facilitation of neurotransmitter releases due to 5-HT3-receptor sensitization by ECT may also play an important role in effective treatment of depressive patients refractory to therapeutic drugs.