Postmeal Optogenetic Inhibition of Dorsal or Ventral Hippocampal Pyramidal Neurons Increases Future Intake

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Neurobiology

Background:

• Meal memory influences future eating behavior, outlasting physiological signals.
• Impaired meal memory encoding in humans leads to increased food intake.
• The specific brain regions mediating memory's inhibitory effect on eating are not well understood.

Purpose of the Study:

• To investigate the role of dorsal hippocampal (dHC) and ventral hippocampal (vHC) glutamatergic neurons in inhibiting energy intake post-meal.
• To test the hypothesis that these neurons are critical for postprandial intake control.

Main Methods:

• Using optogenetics in male Sprague Dawley rats to inhibit dHC and vHC glutamatergic neurons.
• Administering viral vectors (CaMKIIα-eArchT3.0-eYFP or CaMKIIα-GFP) and fiber optic probes.
• Measuring food intake after chow, sucrose, or saccharin meals under different inhibition conditions.

Main Results:

• Inhibiting dHC or vHC neurons after a meal accelerated the next meal's onset and increased consumption.
• Inhibition during a meal hastened meal initiation but did not affect intake during or after the meal.
• These effects were observed when neuronal inhibition was no longer active.

Conclusions:

• Activity in dHC and vHC glutamatergic neurons during the postprandial period is essential for limiting subsequent food intake.
• These neurons likely inhibit future eating by consolidating memories of preceding meals.