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Temporal and pharmacological parameters of puromycin-induced amnesia
Abstract:
Mice were trained in step-down passive avoidance behavior. Bitemporal injections of puromycin (PM) were given either immediately or delayed until 24 hrs after training. PM produced a marked amnesia in both cases during retention testing 3 days later. The amnesia persisted during a second retention test 6 days after training. Of all the antibiotics, only PM is effective as an amnestic agent when injections are delayed 24 or more hours after training. cycloheximide (CXM) was also injected bitemporally immediately after training. However, CXM produced a weaker amnestic effect even though it produced a much greater inhibition of cerebral protein synthesis, more rapidly, and of longer duration. In an effort to attenuate the amnesia produced by PM, in separate experiments, the mice were injected with combined injections of PM and and CXM (bitemporally): mice were also given combined injections of PM (bitemporally) and amphetamine (subcutaneously). The amnesia produced by immediate injections of PM wa not attenuated by either CXM or amphetamine. However, the amnesia produced by delayed injections of PM was attenuated by both CXM and amphetamine. These results suggest that delayed injections of PM (25 hours after training) block the expression or retrieval of memory. This study also supports the contention that puromycin has two separate effects on memory with different temporal parameters depending on when the drug is injected relative to initial training.
Insights
Puromycin (PM) causes amnesia in mice, with delayed injections impacting memory expression or retrieval. Combined with cycloheximide (CXM) or amphetamine, delayed PM injections showed attenuated amnesia, suggesting distinct drug effects on memory.
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- Memory consolidation is a complex process.
- Puromycin (PM) and cycloheximide (CXM) are antibiotics that affect protein synthesis.
- Understanding the temporal dynamics of amnesic agents is crucial for memory research.
Purpose of the Study:
- To investigate the amnestic effects of puromycin (PM) when administered at different time points relative to training.
- To explore the potential for cycloheximide (CXM) and amphetamine to attenuate PM-induced amnesia.
- To elucidate the mechanisms underlying puromycin's effects on memory formation and retrieval.
Main Methods:
- Mice were trained in a step-down passive avoidance task.
- Bitemporal injections of puromycin (PM) were administered immediately or 24 hours after training.
- Cycloheximide (CXM) was administered immediately after training.
- Combined injections of PM with CXM or amphetamine were tested.
- Retention was tested at 3 and 6 days post-training.
Main Results:
- Puromycin induced amnesia regardless of whether it was administered immediately or 24 hours after training.
- Cycloheximide produced a weaker amnestic effect than puromycin, despite greater protein synthesis inhibition.
- Amnesia from immediate puromycin injections was not attenuated by CXM or amphetamine.
- Amnesia from delayed puromycin injections was attenuated by both CXM and amphetamine.
Conclusions:
- Delayed puromycin injections appear to block memory expression or retrieval rather than initial consolidation.
- Puromycin exhibits distinct effects on memory depending on the timing of administration relative to training.
- This suggests two separate mechanisms of action for puromycin on memory processes.