Nutrient responding peptide hormone CCHamide-2 consolidates appetitive memory

Area of Science:

• Neuroscience
• Endocrinology
• Behavioral Genetics

Background:

• CCHamide-2 (CCHa2) is an excitatory peptide found in arthropods.
• In fruit flies, CCHa2 regulates endocrine signaling for development and energy balance.
• Nutrient status influences the formation of odor-sugar associative long-term memory (LTM).

Purpose of the Study:

• To investigate the role of CCHa2 in linking metabolic signals to memory formation.
• To determine if CCHa2 is involved in the consolidation of appetitive memory.
• To identify the neural circuits through which CCHa2 influences memory.

Main Methods:

• Utilized mutant fruit fly strains to genetically disrupt CCHa2 function.
• Employed post-learning thermal manipulation to control CCHa2-expressing cell activity.
• Investigated the expression patterns of the CCHa2 receptor (CCHa2-R) in dopamine neurons.
• Assessed the impact of CCHa2 disruption and manipulation on short-term memory (STM) and LTM.

Main Results:

• Genetic disruption of CCHa2 abolished appetitive LTM but not STM.
• Suppression of CCHa2 cells post-learning impaired LTM formation.
• Activation of CCHa2 cells stabilized STM into LTM, particularly with non-nutritious sugar.
• CCHa2-R is expressed in dopamine neurons crucial for reward-mediated LTM, and its expression is necessary for LTM.

Conclusions:

• CCHa2 signaling is critical for the consolidation of appetitive LTM in fruit flies.
• CCHa2 acts by conveying sugar nutrient signals to dopamine neurons involved in reward.
• This study reveals a direct link between the brain's reward system and the endocrine system for long-term energy homeostasis.