Animal models apparatus

Another experimental animal model for exploring the reinforcing effects of drugs of abuse is the conditioned place preference (CPP) procedure. A distinctive environment (e.g., one compartment of a two- or three-compartment apparatus) is paired repeatedly with administration of a drug, and a different environment is repeatedly associated with administration of vehicle. CPP occurs when repeated administration of a drug in this particular environment results in the ability of that environment to elicit approach behavior and increased time contact (place preference) in the... 

Artificial membranes soaked in animal mucin dispersions or animal model mucosae are used as biological substrates. Another apparatus proposed for in vitro measurements of bioadhesive properties of liquid formulations (polymer solutions or pessaries upon melting) consists of a thermostated inclined plane over which a mucosal membrane or a mucin film is layered. This test measures, as a function of time, the amount of formulation that after contact with the biological substrate, drops on a microbalance placed under the inclined plane [86] (Figure 22.3). 

Presently, relatively little is known about the potency of drugs of abuse after inhalation or smoking. In order to deter-mine the relationship between volatility and pharmacological potency by the inhalation route, the authors developed an animal model to approximate the conditions of human inhalation. The approach involved a volatilization-inhalation drug delivery system developed over the past 10 years in this laboratory. The design of this inhalation apparatus is illustrated in figure 2. 

This ethological model of anxiety measures the activity and time spent in brightly lit vs. dark compartments of the apparatus and is based on the animal s innate desire to explore novel areas (5, 12). Anxious mice exhibit a profound preference for the dark area and display fewer exploratory behaviors (e.g., horizontal activity, vertical rears or wall leans) in the light. Increased duration of time spent in the light area and more exploratory behaviors can be seen following anxiolytic drug administration. 

Low motor or vertical activity may be a strain-specific phenotype. Inactive strains will produce less activity overall and may not be suitable for this model. Likewise, hyperactive strains generally display less non-horizontal exploration and may have difficulties with balance. A narrower apparatus will encourage the animal to show less horizontal activity, enabling it to focus on other behavioral responses. Differences in mouse size should also be addressed. Use animals of similar size, age, and weight to accurately compare between groups. 

Rats are placed on a rod (diameter 7 cm) rotating at a speed of 12 revolutions per minute for a 2 minute period (first habituation session). The rotarod apparatus we use consists of 4 positions separated by a screen, permitting the automatic measurement of 4 animals simultaneously (Ugo Basile, Model 7750). If the rats fall off during this period they are replaced on the rod. At the end of the first habituation session, rats are placed on the rod under the same conditions as used during the test session (i.e. for a maximum of 3 minutes) but are not replaced on the rotarod if they fall off (second habituation session). 

The difficulties in conducting these pharmacokinetic assays - collecting excrement for relatively long period of time (24 h +), requirements for specialized cages and specialized protective apparatus, and the increased space requirements for housing animals individually -has led to the use of other in vivo assays and to the development of in vitro models. 

A small-scale chain conveyor type of extractor was developed in the 1940s at Iowa State University with the intent of using trichloroethylene solvent to extract soybeans. Crown Iron Works of Minneapolis, Minnesota, licensed the technology and extractor design, and supplied several continuous solvent extraction plants in 1951 using the new extractor and trichloroethylene solvent (6). The meal from these plants proved detrimental to animals, so the plants were either closed or converted to petroleum-based solvents (7). The chain-type extractor apparatus continued on and is the basis of the modern Crown Iron Works Model III extractor used today. 

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