Effects of Pair Housing on Patency of Jugular Catheters in Rats (Rattus norvegicus)

Chronic vascular access devices are widely used in a variety of species for repeated blood sampling or substance administration. Jugular catheters are commonly used for studying addiction-related behaviors in rats. Rats with catheters have historically been individually housed for the duration of the study to prevent cage mates from damaging the catheter. The 2 goals of this study were to determine 1) the effects of pair housing on catheter patency and 2) the effects of pair housing on catheter patency of rats in a study of opioid self-administration and cue-induced reinstatement of opioid-seeking behavior. The latter study also represented an opportunity for experimental refinement as it evaluated the temporary use of a barrier that allowed for pair-housed rats to be physically separated. Male Heterogeneous Stock (HS; n = 24) and Sprague–Dawley(SD; n = 121) rats were allocated to either single- or pair-housed condition. To assess the effect of social housing on catheter patency, rats (HS, n = 24; SD, n = 36) were monitored in their assigned housing condition for one month, with scheduled evaluation of catheter patency and structural damage. To examine the effect of social housing on catheter patency during a study of opioid self-administration and cue-induced reinstatement of opioid-seeking behavior, rats (SD, n = 85) were monitored in their assigned housing condition with similar routine patency evaluations. Catheter patency rates between single- and pairhoused rats were not statistically different in the first experiment, and pair-housed animals were successfully maintained on an infusion study in the second experiment. The use of a barrier between pair-housed rats after surgery allowed continued social contact with no observed adverse effects. These results suggest that, pair housing is a viable option for rats with chronicvascular implants, and may improve their wellbeing by allowing them to display species-typical social behaviors.

Case Report: Canine Strain– and Study Condition–Dependent Formation of Renaut Bodies in Sciatic Nerves of Beagle Dogs

Two beagle dog strains were used in a 14-day intrathecal infusion study for a small molecule test article. A moderate number of Renaut bodies (RBs) were observed in the sciatic nerves of control and test article–treated adult animals as early as 1 day after test article infusion (ie, 5 days after catheter implantation in the lumbar cistern). In most cases, the sciatic nerve was affected unilaterally, apparently in association with extended lateral recumbency on one side. The lighter beagle strain (Marshall), and especially the females (which weighed less than age-matched Marshall males), developed more RBs. In contrast, neither females nor males of the larger strain (Harlan) developed any nerve lesions. These data support the hypothesis that RBs develop following mechanical stress to sciatic nerves, suggest that this change may develop fairly quickly following an insult, and demonstrate that different dog strains exhibit strain-specific nerve changes.

Peripherally Inserted Central Catheter Experience in Long-Term Home Parenteral Nutrition Patients

Parenteral nutrition is administered through a central venous catheter(CVC). Peripherally inserted central catheters (PICC) are appropriate for home parenteral nutrition (HPN). The objective of this study was to examine a group of HPN patients with a PICC in place for more than six months, and the complications associated with PICC removal. Medical records from one home infusion pharmacy were retrospectively reviewed for PICC characteristics and complications leading to removal. Nineteen adult HPN patients had 26 PICC placements. Total PICC days were 22,262 with a mean of 856 (265–2500) days. Seven PICCs were in place for 3 to greater than 5 years. The overall complication rate was 0.58/1000 CVC days. Catheter related bloodstream infection (CRBSI) was the main cause of PICC removal. There was no evidence of symptomatic thrombosis. Patients experienced no infusion related complications. The PICCs were 88% polyurethane, 65% double lumen, and 54% were 5 Fr. No patient received alcohol or antibiotic lock therapy, and 8 patients had successful alteplase administered at least one time. All patients needed caregiver assistance for site care and dressing changes, but were independent in HPN infusion and flushing. This group of patients demonstrated that PICCs are a viable option HPN administration. The PICC overall complication rate was very low, and the most frequent complication leading to removal was CRBSI. The infection rate of 0.36/1000 CVC days is considered very low in an HPN population. This is the only HPN infusion study to date reporting 7 PICCs lasting 3 or more years, with 2 lasting greater than 5 years without complications resulting in removal. Patients received their prescribed therapy reliably and without interruption with this device. Larger studies are needed to confirm the efficacy of maintaining a PICC for very long-term HPN administration.

Endogenous GLP1 and GLP1 analogue alter CNS responses to palatable food consumption

Glucagon-like peptide-1 (GLP1) affects appetite, supposedly mediated via the central nervous system (CNS). In this study, we investigate whether modulation of CNS responses to palatable food consumption may be a mechanism by which GLP1 contributes to the central regulation of feeding. Using functional MRI, we determined the effects of endogenous GLP1 and treatment with the GLP1 analogue liraglutide on CNS activation to chocolate milk receipt. Study 1 included 20 healthy lean individuals and 20 obese patients with type 2 diabetes (T2DM). Scans were performed on two occasions: during infusion of the GLP1 receptor antagonist exendin 9–39 (blocking actions of endogenous GLP1) and during placebo infusion. Study 2 was a randomised, cross-over intervention study carried out in 20 T2DM patients, comparing treatment with liraglutide to insulin, after 10 days and 12 weeks. Compared with lean individuals, T2DM patients showed reduced activation to chocolate milk in right insula (P = 0.04). In lean individuals, blockade of endogenous GLP1 effects inhibited activation in bilateral insula (P ≤ 0.03). Treatment in T2DM with liraglutide, vs insulin, increased activation to chocolate milk in right insula and caudate nucleus after 10 days (P ≤ 0.03); however, these effects ceased to be significant after 12 weeks. Our findings in healthy lean individuals indicate that endogenous GLP1 is involved in the central regulation of feeding by affecting central responsiveness to palatable food consumption. In obese T2DM, treatment with liraglutide may improve the observed deficit in responsiveness to palatable food, which may contribute to the induction of weight loss observed during treatment. However, no long-term effects of liraglutide were observed.