Administration of unmodified ECS may lead to spinal fracture and paraplegia in a small percentage of rats. In our experience, the risk is greater in very young animals and when higher stimulus doses are used; however, old animals and those with greater muscle mass are also at risk. Administration of modified ECS is difficult. Ventilating a paralyzed rat before and after the ECS poses problems, and the use of anesthesia may enhance the ECS-induced cognitive deficits (Miller et al., 1985). While the latter may be desirable because it makes the model more representative of clinical contexts, results may actually be inconsistent. Some studies have reported less amnesia with the use of anesthesia, and even the elimination of convulsion (Fochtmann, 1994).

Making an ECS schedule representative of clinical contexts is not easy. We have observed that the administration of alternate-day ECS does not reliably induce amnesia with the models of cognition that we have studied. In this regard, models of retrograde amnesia pose particular problems. The number and frequency of the ECS administered must ideally mimic a clinical course of treatments; however, employing such a schedule of ECS risks introducing time-dependent forgetting of pre-ECS learning. We have therefore administered daily ECS, and sometimes even twice daily ECS, with the (unproven) assumption that the mechanisms of ECS-induced amnesia are similar, provided that the number and frequency of ECS do not differ too widely from clinical norms.

Care must be taken to ensure that the interval between the administration of ECS and subsequent exposure of the rat to the learning task is consonant with the aspect of memory that is being studied. Early exposure to the task is relevant to the transient, postictal cognitive effects of ECT while later exposure is relevant to the more enduring deficits.

Finally, just as learning assessments are best conducted at a fixed time of day, ECS should ideally be administered at a fixed time. This is because variations in ECS-induced seizures have been noted at various points in the diurnal cycle. These variations have been attributed to endogenous opioid levels (Oliverio et al., 1985).

Conclusion

In this article, we have briefly introduced the practice of herbal medicine in India, summarized the studies that have examined the herbal attenuation of amnestic deficits induced by ECS, and discussed the application and limitations of animal models in the context of such research. We have primarily focused on our own work and insights, and have also examined practical issues that are involved in studies of this nature. For a comprehensive review of the effects of ECS on memory and cognition, the effects of pharmacological agents on ECS-induced memory deficits, and the effect of coadministered drugs on ECS seizure properties, the reader is referred to Krueger et al. (1992) and Fochtmann (1994).

Acknowledgment: This article was supported in part by a grant from the Council for Scientific and Industrial Research (CSIR), New Delhi, India.

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