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34.4 ± 0.2*

0.6 ± 0.1

35.5 ± 0.2a*

0.7 ± 0.2

aA significant difference (p< 0.05) from the corresponding wild-type dose. *A significant difference (p< 0.05) from the vehicle treatment of the same genotype.

aA significant difference (p< 0.05) from the corresponding wild-type dose. *A significant difference (p< 0.05) from the vehicle treatment of the same genotype.

on SIH in either genotype, but reduces core body temperature at the highest dose in both genotypes. There was no systematic difference in the basal body temperature of both genotypes, although in one experiment (alcohol) 5-HT1AKO mice had significantly higher body temperature than WT mice. These data confirm and extend earlier findings (Pattij et al, 2001, 2002) that 5-HT1AKO mice do not have an "anxious" phenotype under nonstress conditions. The basal circadian body temperature of 5-HT1AKO mice is not different from WT mice (Pattij et al, 2002; this study) and the response of 5-HT1AKO mice to a mild stressor (rectal probe insertion) is not exaggerated. Moreover, the GABAA-benzodiazepine receptor complex in these mice reflects a normal pharmacological response to various ligands. Non-subunit-specific GABAA-benzodiazepine receptor agonists (diazepam, alprazolam), alcohol, the GABAA-benzodiazepine receptor antagonist fluma-zenil, and pentylenetetrazol have comparable effects in both genotypes. Earlier findings (Sibille et al, 2000; Toth, 2003) in 5-HT1AKO mice on a Swiss-Webster genetic background showed disturbances in this GABAA-benzodiazepine receptor complex, suggesting a causal relationship between the enhanced anxiety observed in the 5-HT1AKO mouse and these disturbances. The present findings in 5-HT1AKO mice on a 129Sv background suggest that such a mechanism not necessarily underlies the putative anxiogenic-like phenotype of 5-HT1AKO mice.

Table 2. Effects of various psychotropic drugs on basal body temperature (T|) and on stress-induced hyperthermia (AT) in 5-HT1B receptor knockout (5-HT1BKO) and wild-type (WT) mice

Drug (route)

Dose (mg/kg)

Wild type

0 0

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