Mechanical restrainers are often utilized in experiments that require the immobilization of animals to carry out precision-based procedures and prevent behaviors that can potentially influence the experimental results. Restraining ensures the safety of the animals and staff while performing processes such as surgery, sample collection, drug administration, and other manipulations. Restrainers are also used in experiments that evaluate stress in animals and in developing stress-related treatments and drugs.
The Bowman restrainer is one of the many available mechanical restrainers in use. The Bowman restrainer is a cylindrical cage with an adjustable diameter. In comparison to other mechanical restraint apparatuses, such as the Flat Bottom restrainer and the Broome restrainer, the Bowman restrainer allows flexibility of using the same device for different weights and sizes of animals within a range. Further, since the apparatus has a cage design, it enables satisfactory dissemination of body warmth. Accessing the different parts of the subject’s body is also easy due to the cage design of the restrainer. This feature, thus, allows numerous kinds of research applications, including blood collection and drug administration at different parts of the body.
Apparatus and Equipment
The Bowman-type restrainer for rodents uses a simple cylindrical cage design to restrain the animal. The apparatus body is made of clear acrylic, and the cage is made using stainless steel rods. The apparatus allows two modes of placement; the animal can be placed in the restrainer either by the removal of the upper poles and placing the poles back in position or by the entry port gap in the back. The front of the cage has a guillotine entryway equipped with a stainless-steel spring stacked bolt. This entryway can be balanced and bolted into three conceivable positions. Suction feet on the base of the apparatus ensure that the device remains secure while in use.
The overall length of the apparatus is 22.8cm, and it has a height of 27.9cm. The rear access port has a diameter of 5.08 cm and allows easy entry for the animal. Eighteen customizable stainless-steel poles that are adjustable to 8.9 cm are used to for the holding cage. The apparatus is capable of restraining animals in the weight range 250 to 750 grams.
Mode Of Operation
The variable bypass vaporizers are the most commonly used vaporizes. Their working principle involves splitting the fresh gas flow and saturating a small portion completely with the volatile anesthetic before recombining into the main gas flow. This process is achieved by setting of the anesthetic concentration using the control dial and the pressurized chamber of the plenum vaporizers. These devices are also equipped with thermo-compensation capabilities for a steady vaporizer output.
Before beginning the process of restraining the animal, ensure that the apparatus is cleaned thoroughly. Place the restraining apparatus on a flat surface. Avoid any sudden and unwarranted behaviors that could startle and stress the animal. A stressed or frightened animal could make handling and restraining procedures difficult. Using an appropriate technique and a firm but gentle grip, pick up the animal from its housing. Generally, the animal can be picked up by placing the thumb and forefinger of one hand around the neck, while supporting its hindquarters with the other hand. Ensure the technique does not cause any injury to the animal.
Place the animal’s mouth close to the restrainer’s rear entry. Gently push the animal into the device while making sure it is not injured by the action. The animals can also be placed into the device by removing the top poles of the cage. Place the animals in the cage and replace the poles back into their position. Ensure the fit is snug.
Prolonged restraining in a mechanical restrainer can be stressful for the animal. It is advisable that the animals are not restrained for more than 30 minutes to prevent unnecessary stress and anxiety. If the animals must be restrained for long periods of time, other less stressful approaches should be considered.
Evaluation of the effect of a single dose of ionizing radiation on gastric secretion
Batzri et al. evaluated the effect of low ionizing radiation on gastric secretory functions in chronic guinea pigs. For the experiment, guinea pigs were surgically implanted with a permanent gastric cannula. Animals were fasted and observed by being restrained in a Bowman restrainer. Each animal underwent unilateral exposure to 400 cGy of total body Cobalt radiation (100 cGy/min). Evaluation of gastric secretions was performed on the day of the radiation and one week later. It was observed that during histamine stimulation, the irradiations inhibited the rise in gastric juice volume. Further, a reduction in normal body weight gain was also observed. It was concluded that an immediate, long-lasting effect of ionizing radiations could be observed on the gastric mucosal functions in guinea pigs.
Assessment of absolute oral bioavailability of ditekiren
Rush et al. evaluated the absolute oral bioavailability of renin inhibitor peptide, ditekiren. Male Sprague Dawley rats that were implanted with the bile duct, duodenum, and superior vena cava cannulae, were used for the investigations. After recovery from the implantation surgery (4 to 5 days), the animals were fasted overnight (with access to water) and placed in Bowman restrainers. Following this, the connector between the bile duct and duodenum cannula was replaced with a spliced extension tubing for bile collection. To compensate for the loss of bile salt and to prevent dehydration, an immediate, continuous infusion of sodium taurocholate through the duodenum cannula was initiated. The subjects were then dosed with ditekiren either orally (p.o.) at 50 mg/kg or intravenously (i.v.) at 10 mg/kg. Results of serum ditekerin and biliary ditekerin quantified by activity and HPLC assay indicated that ditekiren was poorly absorbed and rapidly cleared once it had entered the circulation system.
Evaluation of analgesic effects of high-intensity infrared laser for acupuncture-like stimulation
Zeredo et al. speculated if a high-intensity infrared laser could produce antinociceptive effects similar to the mechanical and thermal stimulation of needles at acupuncture points. For their study, male Sprague-Dawley rats were divided into three groups; laser, needle and restraint group. All the subjects were restrained in a Bowman restrainer for 10 minutes during which they received either laser or needle acupuncture treatment on a point equivalent to the Taixi in traditional acupuncture charts. The restraint group only received random manipulation of their paws. A pulsed erbium YAG laser system (wavelength 2.94 μm, 65 mJ/pulse at 3 pulses per second) was used to irradiate the area to reach a temperature of 45 ±1°C from a 5 mm distance. The subjects were then tested in the tail-flick test to evaluate the anti-nociceptive effects, 60 minutes after restraint. The result suggested that both methods were effective in producing analgesia effects immediately after the treatment. Further, it was also observed that the laser stimulation’s effect was still observable 45 minutes after the treatment.
Animals should be allowed to acclimate to their new environment for at least three days if they are shipped in. Further, they should also be habituated to handling. This ensures that the animal does not suffer from undue stress and anxiety.
Animal’s psychological state and innate behavior must be considered before approaching them and restraining them. The animals must be approached appropriately, avoiding any issues such as loud noises and sudden movements, that can potentially stress or frighten them. Always hold the animals with a firm but gentle grip, taking precaution to prevent any handling injuries. For certain animals, it might be advisable to seek assistance from fellow staff to restrain them. Restrainer should be adjusted to accommodate the size of the animal to prevent respiration issues or escaping. In case the animal must be restrained for a prolonged period, chemical restraining may prove to be a better option than physical restraint.
Strengths and Limitations
The Bowman restrainer is designed using clear acrylic and stainless-steel pole cage which gives visual access to the status of the animal and provides easy access to the animal. The design also permits balancing and bolting of the guillotine front entryway into three conceivable positions, which helps prevent escaping. The suction feet ensure that the apparatus remains secure and stable during the procedures. The removable poles allow an easy, alternate route for placing the animal in addition to the rear entry. Limiting the mobility of the animal ensures that the procedures are performed with precision and without causing damage to the subject.
While using a mechanical restrainer, it must be ensured that the cage fits snuggly and is not too small for the animal. Small sized restrainers may cause respiratory issues while larger sizes may not sufficiently restrain the animal and may even allow escape. Prolonged restraining can be a significant stressor for the animals which can have a potential effect on the research data. Stressful restraint can lead the animal to get stressed out and hide signs of pain and illness. Chemical restraining or other less stressful methods of restraining should be considered in case of prolonged restraining of the animal.
- Restraint techniques help prevent the animal from making unnecessary movements that can cause them injury or injure the staff.
- Bowman-type restrainer uses a stainless-steel pole cage to restrain the animal.
- The cage design provides the researchers with visual access to the animal to observe its status during the procedures and provides greater access to the animal.
- Placement of the animal in the restrainer can be done by removal of the top poles of the cage or via the rear entry port.
- The guillotine front entryway with stainless-steel spring stacked bolt allows balancing and bolting of the door into three conceivable positions.
- Physical restraint is not recommended for prolonged restraining.
- Prolonged restraining can result in significant stress to the animal which consequently will affect the research.
- The handling of the animals should take into consideration their innate behavior.
Batzri S and Catravas G (1988). Inhibition of gastric secretion in guinea pig by relatively low dose ionizing radiation. Proc Soc Exp Biol Med. 189(2):255-60.
Rush B.D, Wilkinson K.F, Zhong W.Z, Closson S.K, Lakings D.B and Ruwart M.J (1991). Absolute oral bioavailability of ditekiren, a renin inhibitor peptide, in conscius rats. Int J Pharm. 73(3):231-237.
Scobie-Trumper, P. (1987). Animal handling and manipulations. In Laboratory Animals: An Introduction for New Experimenters, 153-170.
Thomas, B., & Tilla, W. (2004). Handling and Restraint. Switzerland: Elsevier.
Zeredo JL, Sasaki KM, Toda K (2007). High-intensity laser for acupuncture-like stimulation. Lasers Med Sci. 22(1):37-41.