Policy
Method of Induction
Monitoring / Premature Euthanasia
Supportive Care
References

Policy

Studies involving animal models of status epilepticus (SE)[1] must be designed and performed with due consideration of minimizing animal discomfort, distress, pain, and mortality consistent with the experimental goals. Studies must be designed to include the least amount of seizure activity for the shortest amount of time to still produce meaningful data. Special monitoring, treatment, and supportive care must be detailed in the ARC protocol.

Major considerations for seizure studies should include the method of induction, the provision of appropriate supportive care (commensurate with the number, duration, and severity of seizures), and criteria for either treatment of the seizure by drug administration (such as diazepam) or euthanasia of the affected animal. Protocols should clearly state the goals of the study and clearly justify the duration of SE required to achieve those goals.

The following information should be reviewed and considered in the preparation of studies involving SE in rodents.

Method of Induction

Different protocols exist for induction of SE, including electrical stimulation, percussion, and exposure to excitotoxic or neurotoxic conditions or substances (see Loscher 2024 for a recent review). It is understood that all such protocols may cause a degree of distress and injury, and may result in the mortality of some animals. However, a method must be selected that achieves scientific objectives with the minimum negative impact on animal welfare.

Monitoring / Premature Euthanasia

During the acute phase of SE, animals must be continuously monitored (remote monitoring is acceptable provided that a rapid response can be initiated if required). If they are in a cage during this time, they should be individually caged to prevent inadvertent injury between animals. Cages should also not contain bedding, which might asphyxiate an animal that cannot raise its head; lining of the cage with paper toweling or disposable blue hospital underpads (chux) is recommended.

To better describe the level of seizure activity, during the acute phase, it is recommended that the activity be staged at a minimum of every thirty (30) minutes, using the scale of Racine (1972):
Stage 1: mouth and facial twitches
Stage 2: clonic head movements
Stage 3: unilateral forelimb clonus followed by contralateral clonus
Stage 4: clonic rearing
Stage 5: loss of postural control

If stage 3 or greater seizures are observed for two (2) or more hours, an anticonvulsant should be used (see Supportive Care below). Withholding of anticonvulsant medication in this instance must be scientifically justified and described in the animal use protocol. Prolonged seizures that cannot be controlled with the use of drugs should be considered as a basis for premature euthanasia of the animal unless scientifically justified. Also, development of seizures, accompanied by tonic flexion and/or extension of the limbs, should also be considered a basis for euthanasia unless scientifically justified.

Following the acute phase, animals should be monitored at least once daily by lab staff, including weekends and holidays; more frequent monitoring may be necessary if animals will remain prone to seizures in the chronic phase. Monitoring checks should be documented either at the room level via a log or cage side by use of DLAM’s pink “Study Related Care / Information” card (Refer to the UCLA Worksafe training “DLAM Cage Side Communication Cards” for more information). Criteria for premature euthanasia during this period should include weight loss of 20% or greater. If transient weight loss exceeding 20% might be expected in the first few days following induction, this should be detailed in the animal use protocol and justified. Excessive frequency and/or duration of seizure activity above expected levels during the chronic phase should also be considered a criterion for premature euthanasia.

Supportive Care

As noted above, special monitoring, treatment, and supportive care for animals that will experience SE is required to control seizures in order to prevent high mortality and must be detailed in the relevant ARC protocol. This should include monitoring and control of body temperature as needed.

Anticonvulsants

Benzodiazepines (such as diazepam) and barbiturates (such as pentobarbital) have proved to efficiently abort or attenuate SE, thus preventing the relatively high mortality associated with prolonged seizures in several models. For example, Gibbs et al. (1997) recommended administration of diazepam at 4 mg/kg IP one hour after excitotoxic injection, repeated at 3 and 5 hours, while Buckmaster (2004) and Han et al. (2009) administered diazepam at 10 mg/kg two hours after onset of stage 3 or greater seizures. In models that may induce SE lasting longer than 2 hours or that may be expected to induce seizures of a high stage, 20-30 mg/kg pentobarbital (i.p.) at an interval greater than 30 minutes following injection has been reported to protect animals from lethal effects of convulsants, while allowing the production of sufficient damage to generate the pathological effects required for experimental study (Han 2009). Hasson (2008) compared both diazepam and pentobarbital treatments in young rats, and information on dosing can be found therein. Be aware that these are controlled drugs in California; consult with the Controlled Substance Program for Research at UCLA regarding obtaining, storing and using these compounds.

Fluid Therapy

As early as one hour following SE development, pharmaceutical-grade isotonic saline or lactated Ringer’s solution (at 0.01 to 0.05 ml/gram body weight) should be administered every 2-3 hours in order to maintain adequate hydration. Fluid administration should continue until the animal is able to drink on its own.

Special Feeding

Because animals are sometimes unable to eat pelleted rodent chow during the recovery phase after SE, provision of liquid or soft food may be necessary for some models. Once the animal is able to drink, supportive beverages such as Ensure (rats prefer the chocolate flavor) or Gatorade (especially the red, fruit juice flavors) may be useful as supplements. Animals may also be offered baby food, or other soft food supplements (such as pelleted diet that has been moistened and mashed with Napa nectar). Oral gavaging of liquid and/or soft food should not be necessary but may be attempted if the animal is unable to drink normally, or consume the softened food; maximum volume for gavaging should not exceed 10 ml/kg (0.01 ml/g). Supplemental feeding must continue twice daily until the animal is able to eat regular pelleted food. Consider the caloric requirements of the animal when planning the feeding schedule (for a mouse, approx. 175 kcal /BWkg0.75, for an adult rat, 114 kcal/BWkg0.75, although this can vary with strain, age, etc) (NRC, 1995).

At any time, investigators may contact the DLAM veterinary staff if they have any questions about the condition of their animals or their special care.

References

  1. Buckmaster PS. (2004). Laboratory animal models of temporal lobe epilepsy. Comp Med. 54:473-85.
  2. Curia G. (2008). The pilocarpine model of temporal lobe epilepsy (invited review). J Neurosci Methods.  172:143-57.
  3. Gibbs JW, Shumate MD, Coulter DA. (1997) Differential epilepsy-associated alterations in postsynaptic GABA(A) receptor function in dentate granule and CA1 neurons. J. Neurophysiol. 77:1924–1938.
  4. Glien M, Brandt C, Potschka H, Voight H, Ebert U, Loscher W. (2001). Repeated low dose treatment of rats with pilocarpine: Low mortality but high proportion of rats developing epilepsy. Epilepsy Res. 46:111-119.
  5. Han SR, Shin C, Park S, Rhyu S, Park J, Kim YI (2009). Differential expression of activating transcription factor-2 and c-Jun in the immature and adult rat hippocampus following lithium-pilocarpine induced status epilepticus. Yonsei Med J. 30:200-5.
  6. Hasson H, Kim M and SL Moshe. (2008) Effective treatments of prolonged status epilepticus in developing rats. Epilepsy & Behavior. 13(1):62–69
  7. Loscher, W. (2024) Mammalian models of status epilepticus – Their value and limitations. Epilepsy & Behavior. Volume 158, September 2024, 109923
  8. National Research Council (US) Subcommittee on Laboratory Animal Nutrition. (1995). Nutrient Requirements of Laboratory Animals: Fourth Revised Edition, 1995. National Academies Press (US).
  9. Nirwan N, Vyas P, Vohora D. Animal models of status epilepticus and temporal lobe epilepsy: a narrative review. Rev Neurosci. 2018 Sep 25;29(7):757-770. doi: 10.1515/revneuro-2017-0086. PMID: 29565791.
  10. Racine, RJ. (1972). Modification of seizure activity by electrical stimulation. II. Motor seizure. Electroencephalography and Clinical Neurophysiology; 32:281-94.

[1] Status epilepticus (SE) is defined as more than 30 minutes of either 1) continuous seizure activity or 2) two or more sequential seizures without full recovery of consciousness between seizures.
Glauser TA. Designing practical evidence-based treatment plans for children with prolonged seizures and status epilepticus. J Child Neurol. 2007;22(suppl 5):38S–46S. doi: 10.1177/0883073807303068

Approved 11/24/03; Revised 12/14/09, 6/8/26