Conflict behavior and the effects of 8-OHDPAT treatment in rats selectively bred for differential 5-HT1A-induced hypothermia

The high DPAT sensitivity (HDS) and low DPAT sensitivity (LDS) rat lines ar e the result of selective breeding for differences in the hypothermic respo nse to acute treatment with the 5-HT1A receptor agonist 8-hydroxydipropylam inotetralin (8-OHDPAT). The HDS rats exhibit a much greater hypothermic res ponse than do the LDS rats. The present study examined conflict anxiety-lik e behavior and the effects of acute challenges with 8-OHDPAT and phenobarbi tal (PhB) on conflict behavior in HDS and LDS rats. Water-restricted (24-h deprivation) KDS and LDS rats were trained to drink from a tube that was oc casionally electrified. The 5 -s bouts of drinking tube electrification occ urred on a fixed interval (FI) 30-s schedule and were signaled by the prese nce of a tone. Under this schedule, responding is suppressed approximately 10 -fold during the tone - on periods compared to the no - tone periods. Af ter two weeks of training in this repeated measures drink suppression confl ict paradigm, the effects of acute challenges with 8 -OHDPAT (30-500 mug/kg , SC, + 10 min) or PhB (20 mg/kg, IF, + 10 min) were determined. In control (i.e., non-drug) conflict test sessions, rats of the HDS line accepted sig nificantly fewer shocks than did rats of the LDS line. Acute treatment with 8 - OHDPAT resulted in a modest increase in punished responding (maximum i ncrease: + 30-40 shocks/ session) in both lines at doses of 60 and 125 mug/ kg. Higher doses produced significant general behavioral disruption and sub stantial reductions in water intake (unpunished responding) in both HDS and LDS rats. Neither the increase in shocks received nor the decrease in wate r intake produced by these 8 -OHDPAT challenges differed between HDS and LD S rats. In both lines, acute PhB treatment resulted in a more dramatic incr ease in punished responding than did 8 - OHDPAT ( + 55 -65 shocks/session) and an increase in water intake. The effects of PhB also did not differ bet ween HDS and LDS rats. These data suggest that the KDS and LDS rats exhibit differences in baseline anxiety- like behavior in the conflict task, but d o not differ in their response to acute challenges with PhB or s-OHDPAT. (C ) 2000 Elsevier Science Inc. All rights reserved.