Celecoxib as an in vivo probe of cyclooxygenase-2 mechanisms underlying retrograde amnesia in an animal model of ECT

Antiamnesic properties of analogs and mimetics of the tripeptide human urocortin 3

Amnesia is a deficit in memory caused by brain damage, disease, or trauma. Until now, there are no successful medications on the drug market available to treat amnesia. Short analogs and mimetics of human urocortin 3 (Ucn 3) tripeptide were synthetized and tested for their action against amnesia induced by eletroconvulsion in mice. Among the 16 investigated derivatives of Ucn 3 tripeptide, eight compounds displayed antiamnesic effect. Our results proved that the configuration of chiral center of glutamine does not affect the antiamnesic properties. Alkyl amide or isoleucyl amide at the C-terminus may lead to antiamnesic compounds. As concerned the N-terminus, acetyl, Boc, and alkyl ureido moieties were found among the active analogs, but the free amino function at the N-terminus usually led to an inactive derivatives. These observations may lead to the design and synthesis of small peptidomimetics and amino acid derivatives as antiamnesic drug candidates, although the elucidation of the mechanism of the action requires further investigations.

Searching for the mechanism(s) of ECT's therapeutic effect

The exact therapeutic mechanism of action of electroconvulsive therapy (ECT) remains unresolved. Numerous psychological theories from decades ago have been proven untrue. In the ensuing years, ECT has been proven to have numerous reproducible effects on brain chemistry, regional brain activity, electroencephalographic sleep stages, and neurogenesis. Clinically, ECT has been shown to have antidepressant, antipsychotic, antimanic, antiparkinsonian, and anticonvulsive effects. It is possible that different biological effects of ECT are responsible for different clinical effects or that several biological effects in concert work together to produce a given clinical effect. This paper comments on the array of possible mechanisms and points toward the future of mechanistic research in ECT.

Orchestrated regulation of Nogo receptors, LOTUS, AMPA receptors and BDNF in an ECT model suggests opening and closure of a window of synaptic plasticity

Electroconvulsive therapy (ECT) is an efficient and relatively fast acting treatment for depression. However, one severe side effect of the treatment is retrograde amnesia, which in certain cases can be long-term. The mechanisms behind the antidepressant effect and the amnesia are not well understood. We hypothesized that ECT causes transient downregulation of key molecules needed to stabilize synaptic structure and to prevent Ca2+ influx, and a simultaneous increase in neurotrophic factors, thus providing a short time window of increased structural synaptic plasticity. Here we followed regulation of NgR1, NgR3, LOTUS, BDNF, and AMPA subunits GluR1 and GluR2 flip and flop mRNA levels in hippocampus at 2, 4, 12, 24, and 72 hours after a single episode of induced electroconvulsive seizures (ECS) in rats. NgR1 and LOTUS mRNA levels were transiently downregulated in the dentate gyrus 2, 4, 12 and 4, 12, 24 h after ECS treatment, respectively. GluR2 flip, flop and GluR1 flop were downregulated at 4 h. GluR2 flip remained downregulated at 12 h. In contrast, BDNF, NgR3 and GluR1 flip mRNA levels were upregulated. Thus, ECS treatment induces a transient regulation of factors important for neuronal plasticity. Our data provide correlations between ECS treatment and molecular events compatible with the hypothesis that both effects and side effects of ECT may be caused by structural synaptic rearrangements.

Administration of a selective glucocorticoid antagonist attenuates electroconvulsive shock-induced retrograde amnesia

Mifepristone, a glucocorticoid and progesterone receptor antagonist, has been shown to attenuate retrograde amnesia induced by repeated electroconvulsive shocks (ECS). We examined the efficacy of CORT 108297, a selective glucocorticoid antagonist, in this regard. Adult, male, Wistar rats (n = 69) received either vehicle or CORT 108297 (1 mg/kg) 2 h before each of 5 once-daily true or sham 30 mC ECS. Recall of previous exposure to a noxious stimulus in a passive avoidance (step-through) paradigm was tested 1 day after the 5-ECS course. Analyses were conducted using recall operationalized in different ways: using the absolute final latency scores; defining adequate recall as a final latency of 30 s or greater; defining perfect recall as a final latency of 180 s; and using visual, subjective assessments of animal behavior. ECS was associated with significant impairment of recall, and this impairment was significantly attenuated by CORT 108297 on all outcome measures (with the exception of the perfect recall analyses, where outcomes narrowly missed statistical significance). In conclusion, these findings strengthen previous data from our laboratory implicating glucocorticoid mechanisms in ECS-induced retrograde amnesia. We suggest that the administration of a selective glucocorticoid receptor antagonist shortly before electroconvulsive therapy (ECT) treatments may attenuate the deleterious effect of ECT-induced acute hypercortisolemia on neural mechanisms involved in learning and memory.

Electroconvulsive therapy-induced persistent retrograde amnesia: could it be minimised by ketamine or other pharmacological approaches?

BACKGROUND

Certain pharmacological agents administered during electroconvulsive therapy may have the potential to prevent persistent retrograde amnesia induced during electroconvulsive therapy. This review examines mechanisms for electroconvulsive therapy-induced retrograde amnesia, and evaluates the suitability of the anaesthetic ketamine for preventing this amnestic outcome.

METHODS

A review of human studies, animal models and theoretical models in light of memory dysfunction following electroconvulsive therapy was conducted. MEDLINE was searched from 1950 to April 2009 using the MeSH terms "electroconvulsive therapy", "memory", "memory short term", "memory disorders", "excitatory amino acid antagonists", and "ketamine". PREMEDLINE was searched using the terms "electroconvulsive therapy", "amnesia" and "ketamine". Additional keyword and reference list searches were performed. No language, date constraints or article type constraints were used.

RESULTS

Disruption of long term potentiation as a mechanism for electroconvulsive therapy-induced retrograde amnesia is well supported. Based on this putative mechanism, an N-methyl-D-aspartate receptor antagonist would appear suitable for preventing the retrograde amnesia. Available evidence in animals and humans supports the prediction that ketamine, an anaesthetic agent and N-methyl-D-aspartate receptor antagonist, could effectively prevent electroconvulsive therapy-induced persistent retrograde amnesia. Whilst there are concerns about the use of ketamine with electroconvulsive therapy, such as possible psychotomimetic effects, on balance this anaesthetic agent may improve or hasten clinical response to electroconvulsive therapy.

CONCLUSIONS

A clinical trial is warranted to determine if ketamine anaesthesia during electroconvulsive therapy can lessen persistent retrograde amnesia and improve therapeutic response. Electroconvulsive therapy with ketamine anaesthesia may provide effective antidepressant action with minimal side effects.