Low-Frequency Oscillations of In Vivo Ambient Extracellular Brain Serotonin

Area of Science:

• Neuroscience
• Neurochemistry

Background:

• Serotonin is a key neurotransmitter influencing numerous brain functions.
• Fast-scan cyclic voltammetry (FSCAV) is used to measure serotonin dynamics.
• Previous work showed FSCAV of basal serotonin levels provides insights into brain health and disease.

Purpose of the Study:

• To investigate low-periodicity fluctuations in mouse hippocampal serotonin levels in vivo.
• To characterize the nature and regulation of these serotonin oscillations.

Main Methods:

• In vivo measurements in mouse hippocampi using fast-scan controlled-adsorption voltammetry (FSCAV).
• Correlation analyses to identify and characterize oscillations.
• Acute administration of a selective serotonin reuptake inhibitor (SSRI).
• Optimization of FSCAV parameters for higher temporal resolution.

Main Results:

• Identified robust, low-periodicity (10-minute period) oscillations in basal extracellular serotonin levels in vivo.
• Oscillations were not observed in vitro and were unaffected by sex or chronic stress.
• Acute SSRI administration altered oscillation frequency, suggesting transporter regulation.
• Higher temporal resolution measurements revealed more pronounced frequency shifts and decreased amplitude.

Conclusions:

• Basal serotonin levels exhibit intrinsic, transporter-regulated oscillations in the hippocampus.
• These findings suggest a potential link between serotonin dynamics and endocrine interactions on a minute-to-minute timescale.
• FSCAV is a valuable tool for studying rapid neurochemical fluctuations.