neurobehavioral effects that the investigator wishes to understand in more detail (for example, drugs that block a particular neurotransmitter receptor system can help to determine the neurotransmitter’s role in modifying specific behaviors),
produce a specific neurological state (such as anxiety)
help researchers to understand the biologic and behavioral consequences and possibilities for therapy. (Weiss and O’Donoghue, 1994.)
Some neurobehavioral experiments involving drug administration use animals that are trained to perform a response that can be measured objectively. The motivation for the response may be delivery of food or water, or a drug, as in drug self-administration studies (see next section). Trained responses usually involve operating a lever or switch. Other dependent variables may also be measured, such as feeding, drinking, locomotion, or exploratory activity (Iversen and Lattal, 1991; van Haaren, 1993; Wellman and Hoebel, 1997). The research methods reviewed here involve a known substantial risk to humans or animals from exposure to drugs and other chemicals. Additional information about behavioral tests that can be used to screen unknown drugs or genetic mutants is provided in Chapter 9.
Situations requiring special housing or feeding arrangements were summarized in the earlier NIH report (NIH, 2002, p. 58):
Exposure to drugs usually necessitates individual housing in order to permit repeated access to each animal for dosing and testing. Individual housing also may be preferred because, in a group situation, drug-altered behaviors may increase an animal’s risk of abuse by cage mates, as well as impair its ability to compete for food. For animals in studies of intravenous drug self-administration or of constant intragastric infusion, the animal may be fitted with a vest and tether apparatus to protect the chronically indwelling cannula. Behavior may be measured in the animal’s living cage, to which devices for presenting stimuli and recording responses have been attached (Ator, 1991; Evans, 1994). Such arrangements may preclude conventional group housing. Experiments in neuropharmacology often employ restricted access to food or water for two purposes: (1) to maintain a consistent motivation of behavioral performance (Ator, 1991) and (2) to standardize content of the digestive tract for uniform absorption and uptake of orally administered drugs. This involves scheduling the availability of food and water but not necessarily deprivation. In addition, for experiments that take place over many weeks, it may be important to keep the total amount of drug delivered relatively constant, even when drug doses are calculated on a per weight basis.