Guinea pigs are timid creatures that share many biological similarities with humans. When accustomed to handling from an early age, guinea pigs tend to be comfortable with being picked up. Despite their docile nature, they are known to have a considerable explorative drive in familiar and safe terrains. They have been used in experimental studies for centuries due to their biological similarities to humans. Past decades saw their use in studies of infectious diseases, such as tuberculosis by Robert Koch in 1882 (Cambau and Drancourt, 2014), and in the development of vaccines. Further, guinea pigs also played a pivotal role in the discovery of Vitamin C (Holst and Frölich, 1907) and continued to have an important role in collagen biosynthesis studies (Barnes, 1975). Although now mostly replaced by rats and mice, guinea pigs are still a primary organism model for juvenile diabetes, tuberculosis, scurvy, and pregnancy complications.
Guinea pig restrainers are often used to prevent movement or behaviors that can potentially influence the experimental results. Restraining of the animal makes the process of examination, collecting of samples, drug administration, therapy, or manipulation easy and safe for both the animal and the staff. Guinea pig restrainers are designed to be humane, size appropriate and safe for the animal. While choosing a restrainer, it is important that the right size is selected, since a small size can result in respiratory issues and larger sizes may allow movements and escape. Other restrainers similar in function to the Guinea Pig restrainer include the Flat Bottom restrainer, the Broome restrainer, and the Bowman restrainer.
Apparatus and Equipment
Guinea pig restrainer is designed using a high-quality clear acrylic that allows the researcher to have visual access to the animal’s awareness and status. The restrainer is a semi-cylindrical apparatus fixed onto a durable flat base. It also comes with adjustable head restraint bars, an adjustable back plate, a locking adjustment pin for neck support and an adjustable formed back support. Further, a non-slip flooring is also provided in the restrainer.
The guinea pig restrainer is available in a range of sizes to provide the perfect fit for the size of the subject used. The sizes available are small for weight range 300-350g (10.16 cm x 17.78 cm), medium for weight range 500-600g (11.43 cm x 20.32 cm), and large for higher weights (11.43 cm x 29.21 cm).
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.
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Guinea pigs are docile animals that are easily frightened. When approaching them, it is important that they are not startled to prevent them from squirming to avoid restraint. Care must also be taken to avoid subjecting the animal to unnecessary stress since this can influence the investigation. Often, animals that are habituated to handling procedures from an early age are more compliant with the procedures.
Before beginning the process of restraining the animal ensure that the apparatus is cleaned thoroughly. Place the restraining apparatus on a flat surface. Approach the animal with confidence without making any loud noises or sudden movements to avoid frightening them. Use a firm but gentle grip to pick up the animal. Place the thumb and forefinger of one hand around the neck, while supporting its hindquarters with the other hand. It is important to constantly support the hind legs of the animal to prevent it from injuring its back. Place the animal’s head near the restrainer’s entry and gently place the animal in the restrainer. Adjust the head restraint bars, the back plate, neck support and back support to provide a snug fit for the animal without causing any distress to it.
It is advisable that the guinea pig not is restrained for more than 30 minutes unless necessary. Restraining the animal for long periods will cause unnecessary stress and anxiety to the animal. If the animals must be restrained for long periods of time, other less stressful approaches should be considered.
Saphenous vein blood sample collection
- Shave (or hair removal cream) the back of the hind leg until the saphenous vein is visible.
- Restrain the animal snuggly in the restrainer.
- Ensure the hind leg is immobilized and apply slight pressure above the knee joint.
- Puncture the vein using a 20G needle and collect the blood sample with a capillary tube or a syringe with a needle.
- Compress the puncture site to stop bleeding.
Evaluation of the effect of stress on Schultz-Dale reaction in aortic rings
García et al. evaluated the effects of stress induced by physical restraint in guinea pigs. Adult male Hartley guinea pigs were sensitized using a single subcutaneous injection of 10 mg/ml of egg albumin dissolved in saline solution and emulsified with complete Freund’s adjuvant. Subjects were individually completely immobilized using a mechanical restrainer for 12 hours per day for 5 days during the light cycle. On the 4th day of stress, the animals were immunized. After each stress session, the animals were returned to their colony room with food and water ad libitum. Two control groups were also advanced; one group was immunized, not stressed, and left undisturbed in the colony room while the other group was immunized and maintained in their home cages from which food and water were daily removed for the same time of the stress period. Ten days after the last stress session, recordings were made. Subjects were killed at 10, 12, 19, 21, and 25 days after stress and the anaphylactic response was assessed. The results suggested that severe restraint stress, prior to active immunization, significantly suppressed the anaphylactic response and that food and water intake disruption did not affect the anaphylactic response.
Evaluation of effects if soman on anxiety-related behaviors
Mamczarz et al. tested the anxiety-related behaviors of male Hartley guinea pigs when exposed to a sub-lethal dose of soman (O-pinacolyl methylphosphonofluoridate) and restraint stress. Guinea pigs received a subcutaneous injection of 0.6xLD50 (16.8 µg/kg) soman or saline between the shoulder blades at ages 35 to 36 days and were observed continuously for 30 minutes. The animals were divided into two groups of which one was left undisturbed in their cages while the other half was placed in restrainers for 2 hours in another room with an ambient temperature of 21 ± 0.5°C. After the 2-hour restraint period, the animals were removed from the restrainer and observed for another 2 hours, after which they were moved to another facility where they were maintained for 3 months. At 2 and 3 months since the injection and stress sessions, animal’s behavioral assessment was performed under different conditions on an open-field and elevated plus maze. Guinea pigs treated with 0.6xLD50 soman did not show any signs of acute intoxication even after 2 hours of restraint.
Evaluation of acute dermal toxicity of nanosilver
Korani et al. assessed the dermal toxicity of nanosilver and silver nitrate (AgNO3) in guinea pigs using acute and sub-chronic tests. Male Hartley albino guinea pigs were divided into two treatment groups; one group was assessed for acute dermal toxicity, and the other was assessed for subchronic dermal toxicity. Animals in the acute dermal toxicity group were tested with 100 μg/mL, 1000 μg/mL and 100 μg/mL of a solution of AgNO3 applied to 10% of the body surface area. After the area was shaved and covered with sterile gas and fixed with cloth glue, animals were placed in a restrainer for 4 to 5 hours, and their skin was studied at intervals of 1, 24, 48 and 72 hours. Observations continued for 14 days. Animals in the other group underwent dermal application of test material at 100, 1000, and 10000 μg/mL and rubbed with 100 μg/mL of AgNO3 solution, five times per week for 13 weeks. Results showed that subchronic treatment group had greater tissue abnormalities than those in the acute treatment group.
Guinea pigs 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.
Guinea pigs are shy animals that they are easily frightened. Thus, care must be taken to avoid loud noises and sudden movements when approaching them and handling them. Always hold them with a firm but gentle grip while supporting their hind legs to prevent back injuries. It is recommended that restraining of guinea pigs is done with assistance. Restrainers should be selected based on the size of the guinea pig to prevent suffocation and escaping. In case the guinea pigs must be restrained for a prolonged period, chemical restraining may prove to be a better option than physical restraint.
Strengths and Limitations
The guinea pig restrainer is designed using clear acrylic which gives visual access to the status of the animal. The design also comes with adjustable aspects (Adjustable head restraint bars, adjustable back plate, locking adjustment pin for neck support and adjustable formed back support) to provide the best fit for the animal. The non-slip flooring helps keep the animal in a stable position while also keeping it calm. Limiting the mobility of the animal ensures that the procedures are performed without causing damage to the subject and with precision.
Choosing an appropriate size of the restrainer based on the weight of the guinea pig used is important. 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 guinea pig which can have a potential effect on the research data. Stressful restraint can lead the guinea pigs 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.
- Guinea pigs are docile animals that share biological similarities to humans.
- Restraint techniques help prevent the animal from making unnecessary movements that can cause them injury or injure the staff.
- Guinea pig restrainer is made of transparent acrylic that allows researchers with visual access to the animal to observe its status during the procedures.
- The restrainer also has adjustable head restraint bars, an adjustable back plate, a locking adjustment pin for neck support and an adjustable formed back support, to ensure a snug fit.
- Physical restraint is not recommended for prolonged restraining.
- Prolonged restraining can result in significant stress to the animal which consequently will affect the research.
- Handling of the guinea pig should take into consideration their timid nature.
- Guinea pigs should always have their hind legs supported when picked up and moved about to prevent injuring their backs.
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