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A Lateralized Odor Learning Model in Neonatal Rats for Dissecting Neural Circuitry Underpinning Memory Formation
Published on: August 18, 2014
5-HT2 receptor involvement in conditioned olfactory learning in the neonate rat pup
J H McLean1, A Darby-King, E Hodge
1Division of Basic Medical Sciences, Memorial University of Newfoundland, St. John's, Canada. mclean@morgan.ucs.mun.ca
Insights
The 5-HT2 receptor is crucial for acquiring olfactory learning in early development. Blocking this receptor before training prevents learning, while blocking it after allows learning, highlighting its role in acquisition.
Area of Science:
- Neuroscience
- Developmental Psychology
- Olfactory Learning
Background:
- Serotonin (5-HT) plays a role in various cognitive functions, including learning and memory.
- 5-HT2 receptors are implicated in neural plasticity and development.
- Conditioned olfactory learning provides a model to study the neurobiological basis of early learning.
Purpose of the Study:
- To investigate the specific role of 5-HT2 receptors in the acquisition of conditioned olfactory learning.
- To determine if 5-HT2 receptor activity is required during the learning or consolidation phase.
Main Methods:
- Subcutaneous administration of ritanserin (a 5-HT2A/2C antagonist) to postnatal day 7 pups before or after olfactory training.
- Direct injection of ritanserin into the olfactory bulb prior to training.
- Assessment of olfactory preference on postnatal day 8.
- Experiments involving 5-HT depletion and agonist administration.
Main Results:
- Pups treated with ritanserin before olfactory training failed to acquire a preference for the trained odor.
- Pups treated with ritanserin after olfactory training successfully learned the odor preference.
- Direct administration of ritanserin into the olfactory bulb blocked learning.
- In 5-HT depleted pups, 5-HT2A/2C agonist administration restored learning.
Conclusions:
- 5-HT2 receptor activity is essential during the acquisition phase of conditioned olfactory learning.
- The olfactory bulb is a key site for 5-HT2 receptor involvement in this learning process.
- These findings underscore the critical role of serotonin signaling via 5-HT2 receptors in early-life learning and memory formation.
Abstract:
These experiments addressed the role of 5-HT2 receptors in conditioned olfactory learning. Ritanserin, a 5-HT2A/2C antagonist, was injected subcutaneously into postnatal day (PND) 7 pups before or after conditioned olfactory training to a peppermint odor. When the pups were tested for olfactory preference on PND 8, those injected with ritanserin before training failed to acquire an odor preference whereas those injected after training learned. This suggested that the 5-HT2 receptor is required only in the acquisition of conditioned olfactory learning. Injection of ritanserin directly into the olfactory bulb before training also blocked preference for the peppermint odor. In pups that had depletion of the 5-HT input to the bulb, subcutaneous injection of a 5-HT2A/2C agonist was sufficient to maintain conditioned olfactory learning, confirming the importance of 5-HT in learning.
