Venipuncture Site Influences Blood-drop Volume in C57BL/6 Mice.

Many experiments require the collection of serial blood samples from mice. However, the size of mice limits the volume of blood that can be safely collected as a survival procedure. In IACUC protocols, investigators may report the amount of blood they collect from mice as a number of drops. Many institutions, including ours, use an anecdotal conversion factor (1drop of mouse blood = 25µL) to ensure that blood-collection volumes are compliant with institutional guidelines. To our knowledge, previous work has not experimentally determined the volume of a drop of mouse blood. In this 10-wk crossover experiment, 2 phlebotomists bled 30 C57BL/6J mice from 3 sites (facial, saphenous, and tail) using one or 2 different needle gauge sizes per site. Male and female mice were weighed weekly and divided among 5 groups (n = 6): left and right tail vein, left and right saphenous vein, and facial vein. A single blood drop from each site was weighed, and the volume of each drop was calculated using the average blood density determined from 8 mice terminally bled at the end of the study. Venipuncture site and side significantly influenced blood-drop weight and thus calculated volume. Facial vein puncture produced the largest drop volume (mean: 21.7µL), followed by the saphenous vein (mean: 9.97µL) and tail vein (mean: 4.96µL). Collection from the facial vein was associated with more hemorrhage and morbidity. Left-sided venipuncture was associated with slightly larger-volume blood drops, though the effect size of side was small. The results of this study may be useful in more accurately estimating blood loss via conversion of drops to volume. Our data indicate that blood collection from saphenous and tail veins minimizes blood loss relative to facial vein puncture and may optimize both serial collection of small-volume blood samples and animal welfare.

Spontaneous Pituitary Neoplasm in Two Female Geriatric Southern Giant Pouched Rats (Cricetomys ansorgei).

Southern giant pouched rats (Cricetomys ansorgei) are a small muroid species native to the sub-Saharan Africa. Their exceptionally developed olfactory system, trainability, and relatively small size makes them useful working animals for various applications in humanitarian work. At our institution, a breeding colony of Southern giant pouched rats is maintained to study their physiology and utility as scent detectors. This case report describes the occurrence of spontaneous pituitary neoplasms with distinct clinical presentations in 2 geriatric (approximately 7.5 y old) wild-caught female Southern giant pouched rats. The first pouched rat displayed vestibular deficits, including left-sided head tilt, ataxia, disorientation, and circling. MRI revealed a large, focal heterogeneous mass arising from the pituitary fossa. The second pouched rat presented with polyuria, polydipsia, and hyperglycemia but no neurologic signs. Examination after euthanasia revealed a prolactin (PRL)-expressing pituitary carcinoma and adenoma in the first and second pouched rat, respectively, associated with mammary hyperplasia in both animals. This is the first report of spontaneous PRL-producing pituitary tumors in Southern giant pouched rats.

Comparison of Effects of Capromorelin and Mirtazapine on Appetite in New Zealand White Rabbits (Oryctolagus cuniculus).

Inappetence is a welfare concern in rabbits (Oryctolagus cuniculus), as it can lead to potentially fatal gastrointestinal stasis. In other species, inappetence is commonly treated with appetite stimulants; however, few published studies have evaluated the efficacy of appetite stimulants in rabbits. We performed 2 studies to evaluate the effects of capromorelin and mirtazapine on appetite in New Zealand White (NZW) rabbits. In the first study, healthy rabbits ( n = 9) were evaluated using a randomized crossover design and 9 treatments: capromorelin 4 mg/kg oral (PO) once a day (SID), capromorelin 8 mg/kg PO SID, saline control PO SID, capromorelin 4 mg/kg PO twice a day (BID), capromorelin 8 mg/kg PO BID, saline control PO BID, mirtazapine 0.5 mg/kg transdermal (TD) SID, mirtazapine 1 mg/kg TD SID, and saline control TD SID for 3 d with a 1-wk washout period between treatments. Treatment efficacy was assessed by measuring daily feed intake and fecal output and by weighing rabbits twice a week. Overall, feed intake and fecal output were higher for all treatments as compared with controls, except for fecal output in the capromorelin 4 mg/kg and 8 mg/kg PO SID groups. Feed intake and fecal output were significantly higher with mirtazapine as compared with capromorelin. Body weight and erythema/petechia of the pinnae were greater in the mirtazapine 1 mg/kg TD SID group than in the control group. A second study evaluated rabbits that had undergone surgery (castration, n = 7) and then received one of 3 treatments: capromorelin 8 mg/kg PO BID, mirtazapine 1 mg/kg TD SID, or saline PO BID for 3 d postoperatively. Feed intake and fecal output in the postoperative mirtazapine group were not significantly different from those of the capromorelin and control groups. Due to its superior efficacy as compared with capromorelin in healthy NZW rabbits, we recommend considering mirtazapine as a treatment for inappetence in NZW rabbits.

Effects of Cisapride, Buprenorphine, and Their Combination on Gastrointestinal Transit in New Zealand White Rabbits.

Due to their effective analgesic properties, opioids are worthy of consideration for pain management in rabbits. However, this class of drugs causes undesirable effects including reduced gastrointestinal (GI) motility, reduced fecal output, and delays GI transit times and thus increases the risk of GI stasis. The risk of stasis discourages the use of opioids in rabbits, which could affect animal welfare. Gastroprokinetic agents such as cisapride are effective in promoting gastric emptying in many species, but whether this effect occurs in rabbits is unknown. This study assessed the efficacy of cisapride when administered as a single agent and in combination with buprenorphine in rabbits; efficacy was assessed by measuring GI transit times, fecal output, body weight, and food and water intake. Female New Zealand White rabbits (n = 10) were studied in a crossover, randomized design and received either vehicle and buprenorphine, cisapride and saline, cisapride and buprenorphine, or vehicle and saline (control) every 8 h for 2 d. Rabbits were anesthetized and administered radio-opaque, barium-filled spheres via orogastric tube. Feces was assessed via radiography for detection of the barium-spheres to determine GI transit time. GI transit time was significantly longer in buprenorphine groups than in control groups, regardless of the use of cisapride. Fecal output and food and water intake were lower for buprenorphine groups than control groups. Cisapride did not significantly alter GI transit, fecal output, or food and water intake. In addition, treatment group did not significantly affect body weight. In conclusion, buprenorphine treatment (0.03 mg/kg TID) prolonged GI transit time and reduced fecal output and food and water consumption in rabbits. Coadministration of buprenorphine and cisapride (0.5 mg/kg) did not ameliorate these effects, and the administration of cisapride at this dose did not appear to affect GI motility in female rabbits.