Functional and structural neural network characterization of serotonin transporter knockout rats

Area of Science:

• Neuroscience
• Genetics
• Neuroimaging

Background:

• Brain serotonin homeostasis is regulated by the serotonin transporter (5-HTT).
• Reduced 5-HTT function is linked to anxiety, depression, and altered responses to stimuli, including cocaine.
• Potential effects on neural wiring in corticolimbic brain structures are not fully understood.

Purpose of the Study:

• To investigate the impact of 5-HTT knockout on brain network organization using MRI techniques.
• To assess functional and structural brain alterations in 5-HTT(-/-) rats compared to wild-type controls.
• To evaluate the effects on resting-state functional connectivity, cocaine-induced activation, and white matter integrity.

Main Methods:

• Resting-state functional MRI (fMRI) to assess baseline connectivity.
• Pharmacological MRI to measure cocaine-induced brain activity.
• Diffusion tensor imaging (DTI) to evaluate white matter structural integrity.
• Graph theory analysis of both functional and structural networks.

Main Results:

• No significant differences in baseline functional connectivity or cocaine-induced neural activity within the corticolimbic network between 5-HTT(-/-) and 5-HTT(+/+) rats.
• DTI revealed largely intact white matter, with a notable exception of reduced fractional anisotropy in the genu of the corpus callosum in 5-HTT(-/-) rats.
• Network analysis indicated similar overall brain network organization between genotypes, despite sensitivity of individual tests to detect moderate effects.

Conclusions:

• The 5-HTT genotype has limited effects on overall MRI-based measures of brain morphology and function.
• Reduced fractional anisotropy in the corpus callosum genu may suggest a subtle impairment in interhemispheric information integration in 5-HTT(-/-) rats.
• Further research is needed to fully elucidate the functional consequences of these subtle structural differences.