Pavlovian conditioning of heart rate and body temperature with morphine: Effects of CS duration.

Abstract

Rats were exposed to a conditioning procedure that varied the duration of overlap between a light-noise conditioned stimulus (CS) and the effects of a morphine (5 mg/kg) unconditioned stimulus (US). Three paired (P) groups differed in CS duration (5, 15, or 60 min) but had the same CS-US interval (30 s). A control group (U) received explicitly unpaired presentations of CS and US. P groups showed CS-specific attenuation of the bradycardic response and enhancement of the hyperthermic response to morphine. During placebo tests, the CS elicited conditioned increases in heart rate and body temperature in Groups P15 and P60. Group P5 showed a conditioned increase in heart rate but not in body temperature. Overall, strength of conditioning was directly related to CS duration. These data indicate that duration of overlap between a CS and drug-induced changes in a target response system is an important determinant of Pavlovian drug conditioning.

Conditioning trial duration affects ethanol-induced conditioned place preference in mice

“…Specifica1ly, astronger preference was observed in mice that had previously received 5-min exposure to the CS after ethanol injection than in mice that had received 30-min exposure to the CS. These findings are generally consistent with other drug conditioning studies showing that CS duration affects strength of conditioning (Paletta & Wagner, 1986;Schwarz-Stevens & Cunningham, 1992). However, these results contrast with two previous studies reporting no effect of conditioning trial duration (range: 10-100 min) on strength of conditioned place preference induced by opiate drugs in rats (Bozarth, 1987;Mucha, van der Kooy, O'Shaughnessy, & Bucinieks, 1982).…”

Reversible inactivation of rostral nucleus raphe pallidus attenuates acute autonomic responses but not their habituation to repeated audiogenic stress in rats

“…This observation may suggest that the repeatedly induced hypothermic responses previously induced by RPa muscimol injections were anticipated by these rats, especially after the simulated injection procedures, resulting in a moderate hyperthermic response. These results are reminiscent of findings from repeated systemic drug injections that modify body temperature and induce conditioned tolerance effects to injection-related environmental stimuli (Miksic et al, 1975, Siegel, 1978, Mansfield and Cunningham, 1980, Crowell et al, 1981, Cunningham et al, 1983, Schwarz-Stevens and Cunningham, 1993). Because of the lack of body temperature measurements from the colony room where animals were housed between experimental manipulations, it is difficult to determine if these temperature regulations were limited to contextual cues or were more pervasive and generalized.…”

Morphine taste conditioning and analgesia: Assessing conditioned and novelty-induced analgesia.

“…Perhaps other stimuli such as odor or tactile cues would more readily serve as a CS in this situation. Clearly, further work exploring parameters such as CS duration or CS-US overlap (e.g., see Schwarz-Stevens & Cunningham, 1993) is required to determine whether or not taste (or other cue modalities) can serve as a CS in a morphine-conditioned analgesia paradigm.…”