N-methyl-D-aspartate (NMDA)-induced seizures in developing rats
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Developing rats are highly sensitive to N-methyl-D-aspartate (NMDA) induced seizures, with younger pups experiencing more severe and frequent motor seizures. Seizure types also change with age, from flexion seizures to generalized tonic-clonic seizures.
Area of Science:
- Neuroscience
- Developmental Biology
- Pharmacology
Background:
- N-methyl-D-aspartate (NMDA) receptor activation is crucial for synaptic plasticity and neuronal development.
- NMDA receptor dysfunction is implicated in various neurological disorders, including epilepsy.
- Understanding age-dependent effects of NMDA is vital for studying neurodevelopmental processes and potential therapeutic interventions.
Purpose of the Study:
- To investigate the age-dependent effects of N-methyl-D-aspartate (NMDA) on seizure induction in developing rats.
- To characterize the types of motor seizures and their progression in different age groups following NMDA administration.
- To determine the sensitivity and lethality of NMDA in young versus adult rats.
Main Methods:
- Intraperitoneal administration of N-methyl-D-aspartate (NMDA) to rats aged 7 to 25 days and adult rats.
- Observation and recording of motor behaviors, including hyperactivity, clonic, tonic, and generalized tonic-clonic seizures.
- Calculation of CD50 (seizure-inducing dose) and LD50 (lethal dose) at different ages.
- Electroencephalogram (EEG) recordings to correlate motor activity with brain activity.
Main Results:
- NMDA induced epileptic motor seizures in all tested age groups, starting with locomotor hyperactivity.
- Younger rat pups (7-25 days) exhibited increased sensitivity to NMDA, with lower CD50 and LD50 values compared to adults.
- Seizure patterns evolved with age: flexion seizures (emprosthotonus) were prominent in early postnatal weeks, replaced by generalized tonic-clonic seizures in older rats.
- EEG recordings showed suppressed activity, indicating a lack of direct correlation between motor seizures and overall brain electrical activity.
Conclusions:
- The developing rat brain is particularly vulnerable to NMDA-induced excitotoxicity and seizures, with sensitivity decreasing significantly with age.
- NMDA receptor-mediated seizure patterns undergo developmental changes, reflecting the maturation of neuronal circuits.
- The observed dissociation between motor phenomena and EEG activity suggests complex NMDA effects on neuronal networks during development.
Abstract:
Intraperitoneal administration of N-methyl-D-aspartate (NMDA) elicited epileptic motor seizures in developing rats aged from 7 to 25 days as well as in young adults. The very first sign of NMDA action is locomotor hyperactivity which is followed by clonic and tonic seizures. In rat pups during the first 3 postnatal weeks flexion seizures (emprosthotonus) appeared as the first pattern of motor seizures; later they were replaced by generalized tonic clonic seizures. Only regular tonic-clonic seizures were observed in 25-day-old and adult rats. The youngest animals are the most sensitive to NMDA. CD50 for tonic-colonic seizures is 6.7 mg/kg in 7-day-old rat pups and it increases up to 86.6 mg/kg in 25-day-old animals. Similar changes could also be demonstrated for LD50, a lethal outcome being very frequent. EEG recordings demonstrated mainly suppressed activity, thus exhibiting a lack of correlation with motor phenomena.