Focal, remote-controlled, chronic chemical modulation of brain microstructures

Area of Science:

• Neuroscience
• Biomedical Engineering
• Pharmacology

Background:

• Direct fluid delivery to brain parenchyma is crucial for research and clinical applications.
• Current methods using acutely inserted cannulas suffer from backflow and poor spatial/temporal control.
• Minimally invasive techniques are needed for precise interfacing with brain microstructures.

Purpose of the Study:

• To develop and characterize an implantable, MRI-compatible, remotely controlled drug delivery system for precise brain infusions in freely moving animals.
• To compare infusion accuracy between acutely inserted needles and chronically implanted probes.
• To demonstrate the impact of precise volume dosing on neural structures and behavior.

Main Methods:

• Development of an implantable, MRI-compatible, remotely controlled drug delivery system.
• Comparison of infusion volumes and dispersion using acutely inserted needles versus chronically implanted probes.
• Characterization of in vivo infusion dynamics using positron emission tomography (PET) with radiolabeled agents (copper-64, fludeoxyglucose).
• Assessment of behavioral changes induced by selective modulation of the substantia nigra via muscimol infusion.
• Evaluation of chronic device viability in rat models up to 1-year implantation.

Main Results:

• Infusions via acutely inserted needles targeted a region more than twofold larger than identical infusions through chronically implanted probes due to reflux and backflow.
• Positron emission tomography accurately quantified infusion volumes as small as 167 nL.
• Selective modulation of the substantia nigra induced volume-dependent behavioral changes, even with constant total dose.
• Chronic device viability was confirmed up to 1-year post-implantation in rats.

Conclusions:

• The developed implantable system provides significantly improved spatial and temporal control over fluid delivery to the brain compared to traditional methods.
• Precise control over drug volume is critical for reliably eliciting behavioral effects and understanding neural circuit function.
• This technology holds promise for advancing preclinical research in neurological diseases and developing more efficacious human therapies.