date, work has consisted of pilot tests to develop appropriate proce-
dures and an initial study to compare copper sulfate, cyclophos-
phamide, lithium chloride, and red squill as aversion-producing drugs.

The procedures developed for these tests involve placing rats on a
daily 22-h water deprivation schedule followed by a 2-h period in
which saccharin-flavored water is available. The preconditioning
phase lasts 14 days. On the treatment day, the rats are presented
with saccharin-flavored water which either contains an aversive drug
or precedes gavage or intraperitoneal injections of the drug.
Subsequently, each rat's saccharin preference is monitored for 28
successive days following the same procedure outlined for the pre-
conditioning phase, but during the 2-h nondeprivation period the
animals have a choice of water or water plus saccharin.

Results of these pilot tests indicate that: (1) ricefield rats will
orally ingest saccharin-flavored water containing lithium chloride,
(2) the mode of drug administration (free ingestion, gavage, or
intraperitoneal injection) affects taste aversion conditioning, and
(3) aversion effects lasting from 19 to 28 days can be produced.

In a study to select a drug that produces a high level of aversion,
42 male rats were randomly assigned to six different drug treatments
(n = 7/group). Gavage dosages of 125 mg/kg lithium chloride, 5 mg/kg
copper sulfate, 33 mg/kg cyclophosphamide, 35 mg/kg red squill, 125
mg/kg sodium chloride, or volumes of water equal to those of the
lithium doses were administered after the 2-h presentation of
saccharin. Results were marginal; lithium-treated rats showed an
aversion to saccharin for approximately 10 days.

Due to the tenuous results obtained in this study, a second trial,
involving increased dosages of drugs, was conducted. Gavage dosages
for this study were: lithium chloride, 375 mg/kg; copper sulfate, 30
mg/kg; cyclophosphamide, 198 mg/kg; red squill, 210 mg/kg; sodium
chloride, 375 mg/kg; and volumes of water equal to the lithium dose.
Figure 1 is a graph of the mean daily aversion indices obtained. As
shown, the lithium chloride rats displayed the most prolonged
aversion to saccharin. Intermediate aversion was noted in rats
treated with cyclophosphamide and red squill; copper sulfate produced
practically no aversion to saccharin, a result similar to that for
sodium chloride and water. Together, these data confirm that lithium
chloride is an effective drug for further studies to evaluate the
concept of drug-induced aversion as a means of protecting field crops
from damage by rodents.