Fj. Files et al., Comparison of alcohol-preferring and nonpreferring selectively bred rat lines. II. Operant self-administration in a continuous-access situation, ALC CLIN EX, 22(9), 1998, pp. 2147-2158
Several rat lines have been developed using preference/nonpreference and da
ily ethanol intake in the homecage as criteria for selective breeding. Usin
g these lines, behavioral and neural factors that may underlie the genetic
basis for the control of ethanol consumption have been examined. In this pa
per, we report data from eight of these selected lines: the Alcohol-Preferr
ing (P) and Alcohol-Nonpreferring (NP), the Alcohol-Accepting (AA) and Alco
hol-Nonaccepting (ANA), and the High Alcohol Drinking (HAD1 and HAD2) and L
ow Alcohol Drinking (LAD1 and LADS) rats. Ali lines were tested using opera
nt procedures and the same protocols for both the ethanol self-administrati
on initiation and measurement of continuous-access ethanol consumption. Dur
ing continuous access, the animals were housed in operant chambers with acc
ess to 10% (v/v) ethanol after responses on one lever, food pellets (45 mg)
after responses on a second lever, and water in a drinking tube that was c
onnected to a drinkometer circuit Under these procedures, both similarities
and differences among the selected lines on continuous-access operant etha
nol intake were observed. For example, overall total homecage ethanol drink
ing was similar for the AA and both HAD lines. When examined in the operant
continuous-access situation, however, the AA rats displayed a different co
nsumption pattern, compared with the HAD lines. Data suggest that the frequ
ency of drinking bouts was a primary factor in the phenotypic homecage sele
ction of the preferring lines that was revealed by the use of the continuou
s-access operant procedure. In general, data suggest that genes related to
ethanol preference and intake in homecage continuous-access situations may
not be identical to those related to ethanol's reinforcing function in oper
ant continuous-access conditions. Because ethanol consumption appears to be
controlled by different drinking patterns across lines, the selected lines
provide for a variety of models to understand how varying genotypes can im
pact ethanol consumption.