Serotonin transporter knockout (KO) mice self-administer less ethanol than either heterozygous or wild-type mice; however, the mechanistic basis for this difference remains unclear. Here we examine the possibility that ethanol more readily decreases responding in KO mice, thereby limiting ethanol self-administration. To examine whether KO mice were more sensitive to the response-decreasing effects of ethanol, we administered ethanol (0.2–3.2 g/kg) to mice responding under a multiple fixed-ratio 30-response, fixed-interval 300-s schedule of milk presentation. Ethanol decreased responding similarly in all three genotypes. Fixed-ratio responding tended to be decreased at lower doses than fixed-interval responding. The decreased level of ethanol self-administration in serotonin transporter KO mice is not explained by an increased sensitivity to the response-decreasing effects of ethanol in KO mice, as sensitivity to the response-decreasing effects of ethanol was similar in the KO, heterozygous, and wild-type mice.
Departments of aPsychiatry
cPharmacology, University of Texas Health Science Center at San Antonio, San Antonio
dDepartment of Behavioral Analysis, University of North Texas, Denton, Texas, USA
Correspondence to Richard J. Lamb, PhD, Psychiatry MC 7792, UTHSCSA, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA E-mail: email@example.com
Received September 11, 2013
Accepted October 18, 2013