CS preexposure: Latent inhibition and Pavlovian conditioning of heart rate and eyeblink responses as a function of sex and CS intensity in rabbits

Abstract

Male and female rabbits received Pavlovian conditioning in which a 1,216 o H z tone served as the CS and a 3 0 m A paraorbital electric shock train served as the US. Eyeblink (EB) and heart rate (HR) CRs were assessed. Half of the animals received prior exposure to the CS, while half were restrained in the chamber for a similar length of time but did not receive prior CS exposure. Different groups of each sex received three different CS intensities including 60,75, and 90 dB (SPL) during both preexposure and conditioning. The results revealed that latent inhibition of the EB CR occurred only at the intermediate CS intensity, as indicated by a significant impairment of EB conditioning in this group. However, the magnitude of the decelerative HR CR was attenuated by prior CS exposure at all three CS intensities. Females showed faster EB conditioning than males, but latent inhibition occurred in both sexes. These results suggest that somatomotor and autonomic systems are affected differently by prior CS exposure.

Sensorimotor enhancement in mouse mutants lacking the Purkinje cell-specific Gi/o modulator, Pcp2(L7)

“…Furthermore, the observation that ASR habituation in mice is a sexually dimorphic behavior that is specific for females suggests a possible explanation for the more dramatic enhancement of tone-shock association in female mutants than males: females as a group have a more adaptable tone response than males and therefore the enhancement in the female mutants is larger. This is consistent with earlier studies showing that female rabbits and rats acquire the conditioned response faster than males in classical eyeblink conditioning (Hernandez et al, 1981; Wood and Shors, 1998). Lastly, the detection of a complex contribution of L7 genotype to hotplate responsiveness suggests that the cerebellum may even modulate the magnitude of responses to solitary sensory stimuli that have no time or integrative component, i.e., that are pure sensory effects.…”

Concomitant eyeblink and heart rate classical conditioning in young, middle-aged, and elderly human subjects.

“…The acquisition functions were also somewhat more gradual in our study than that reported by either Woodruff-Pak and Thompson (1988) or Solomon et al (1989), but this was probably attributable to habituation of the alpha EB response and the HR OR in our study but not in prior studies. It is well established that CS preexposure results in delayed acquisition of both somatic and autonomic Pavlovian CRs (e.g., Hernandez, Buchanan, & Powell, 1981).…”

Morphine promotes autonomic learning.

“…Stress also evokes endogenous opioid analgesia, and reexposure to associated cues evokes conditioned opioid analgesia and enhances morphine analgesia by similar mechanisms (e.g., Fanselow & Kim, 1994;Hammack et al, 1999;Rosellini, Abrahamsen, Stock, & Caldarone, 1994). Certain gender differences in Pavlovian HR and eyeblink conditioning also occur in normal rabbits (e.g., Herna ´ndez, Buchanan, & Powell, 1981;Powell, Buchanan, & Herna ´ndez, 1991). Therefore, we conducted supplemental analyses of the present data that included gender as a factor, but there were no significant interactions with morphine dose effects on HR discrimination or on HR OR or CR magnitude during training, indicating that these effects were the same in both genders.…”