Novel intrathecal and subcutaneous catheter delivery systems in the mouse

Abstract

Background: Catheter systems that permit targeted delivery of genes, molecules, ligands, and other agents represent an investigative tool critical to the development of clinically relevant animal models that facilitate the study of neurological health and disease. The development of new sustained catheter delivery systems to spinal and peripheral sites will reduce the need for repeated injections, while ensuring constant levels of drug in plasma and tissues.

New method: Here, we introduce two novel catheter delivery systems in the mouse: the O'Buckley intrathecal catheter system for sustained delivery to the spinal region and a subcutaneous bifurcated catheter system for sustained drug delivery to both hindpaws.

Results: The O'Buckley intrathecal catheter system consistently distributed Evans Blue throughout the spinal cord, with the greatest concentration at the thoracic region, and with an 85% surgery success rate. The subcutaneous catheter system consistently distributed Evans Blue to the hindlimbs, with a 100% surgery success rate.

Comparison to existing method: The O'Buckley intrathecal catheter system accomplishes sustained drug delivery to the spinal region, with a 2-fold increase in surgery success rate, as compared to the traditional method. Our subcutaneous bifurcated catheter system accomplishes sustained drug delivery to both hindpaws, eliminating the need for repeated intraplantar injections.

Conclusions: We have developed catheter systems that improve upon traditional methods in order to achieve sustained localized drug delivery to spinal tissues and to hindpaw tissues surrounding peripheral sciatic nerve terminals. These methods have a broad reach, and can be used to enhance behavioral, physiologic and mechanistic studies in mice.

Keywords: Bifurcated; Continuous infusion; Drug delivery; Hindpaw; Mouse; Osmotic pump; Peripheral; Routes of administration; Spinal cord; Surgical methods.

Figure 1. Novel i.t. and s.c. catheter delivery systems in mouse

This schematic illustrates the catheter systems designed to achieve consistent delivery of drug (A) intrathecally throughout the spinal cord and (B) subcutaneously to both hindpaws. Dotted yellow lines indicate portions of the catheter underneath occipital tissue or vertebrate bone, while solid yellow lines indicate s.c. portions of the catheters.

Figure 2. Modified intrathecal catheter system allows for sustained delivery of Evans Blue to the spinal cord

The O’Buckley i.t. catheter system (A–C) is shown, along with side (B) and dorsal (C) views of catheter placement within the condylar canal. The O’Buckley i.t. catheter system successfully achieved sustained delivery of Evans Blue dye throughout the spinal cord (D). Images B–D were taken on Day 7 following catheter implantation. White arrows indicate the i.t. catheter insertion site, yellow arrows indicate the A-O membrane, and the blue arrow indicates the i.t. catheter underneath intact A-O membrane.

Figure 3. O’Buckley intrathecal catheter system does not produce mechanical pain behaviors in mice

Surgical implantation of the O’Buckley i.t. catheter system for sustained delivery of saline to the spinal cord does not produce (A) altered mechanical thresholds, (B) mechanical allodynia or (C) mechanical hyperalgesia on Days 2, 4, 6 and 8 following surgery, as compared to baseline. N=6. Data are expressed as mean ± SEM.

Figure 4. O’Buckley intrathecal catheter system does not produce fibrosis or inflammation in mice

Both mice that received sustained i.t. administration of saline and their naïve controls demonstrated normal tissue composition and no structural abnormalities in the spinal cord (A–B) or brainstem (C–D).

Figure 5. Subcutaneous bifurcated catheter system allows for sustained delivery of Evans Blue to both hindpaws simultaneously

A novel s.c. bif. catheter system (A–C) was implanted in mice using a stainless steel trocar (B) for guidance. Sutures were used to fasten the catheter to surrounding fascia of the hindpaws, as denoted by the white circle (C). The s.c. bif. catheter system successfully achieved sustained delivery of Evans Blue dye to both hindlimbs (D). Evans Blue dye was observed as early as Day 2 following catheter implantation and lasted until Day 7. Image in (D) was taken on Day 7.

Figure 6. Bifurcated subcutaneous catheter system does not produce mechanical pain behaviors in mice

Surgical implantation of the s.c. bif. catheter system for sustained delivery of saline to both hindpaws does not produce (A) altered mechanical thresholds, (B) mechanical allodynia or (C) mechanical hyperalgesia on Days 1, 3, 5 and 7 following surgery, as compared to baseline. N=8. Data are expressed as mean ± SEM.

Figure 7. Bifurcated subcutaneous catheter system does not produce edema of the hindlimbs, hocks, or hindpaws

Surgical implantation of the s.c. bif. catheter system for sustained delivery of saline to both hindpaws does not cause edema of the left or right (A) hindlimbs, (B) hocks or (C) hindpaws of mice on Days 1, 3, 5 and 7 following surgery, as compared to baseline. N=5. Data are expressed as mean ± SEM.

Figure 8. Sustained subcutaneous administration of bupivacaine decreases responses to mechanical stimuli equally in both left and right hindpaws

Surgical implantation of the s.c. bif. catheter system for sustained delivery of bupivacaine to both hindpaws produces (A–B) increased mechanical thresholds and (C–D) decreased mechanical hyperalgesia on Days 1, 3, 5 and 7 following surgery, as compared to baseline. N=5. Data are expressed as mean ± SEM. **p<0.01, *p<0.05 indicates significant difference from saline treated mice.