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At least 289 records · Page 16Linked to original sources
PubMed1994

Effects of midazolam and naloxone in rats tested for sensitivity/reactivity to formalin pain in a familiar, novel or aversively conditioned environment.

Rats tested for sensitivity/reactivity to formalin-induced pain in either an aversively conditioned or a novel environment displayed immediate but transient hypoalgesic responses that were insensitive to either a benzodiazepine (midazolam) or an opioid antagonist (naloxone). Exposure to the aversively conditioned, but not to the novel environment also provoked a more enduring hypoalgesic response that was abolished by either midazolam or naloxone. The results were taken to mean that fear is sufficient but not necessary for the production of hypoalgesic responses to environmental stimuli.

Analgesia↗
PubMed1982

Sex differences in biobehavioral responses to conflict in a taste aversion paradigm.

A conditioned aversion to a novel milk solution was produced, and animals were then reexposed to milk while nondeprived (low conflict) or following a 72-hr food and water deprivation regimen (high conflict). No sex differences occurred if animals were nondeprived throughout testing. However, if deprived during the interval between conditioning and reexposure, sex differences in both behavior and adrenocortical responses occurred: (1) Presession corticoid levels of females were higher than those of males. (2) On the first reexposure day, females showed a suppression of plasma corticosterone below presession levels, while males maintained elevated or increased corticosterone levels. (3) On the second reexposure day, when no longer deprived, males showed a marked suppression of intake compared to females, and females subsequently recovered to pretoxicosis intake levels faster than males. (4) Gonadectomy eliminated these sex differences. While ovariectomized females continued to resemble intact females in both behavioral and hormonal responses, castrated males exhibited a corticoid suppression on the first reexposure day, and subsequently recovered to pretoxicosis intake levels at the same rate as females.

Animals↗
PubMedDate not supplied

Comparison of the discriminative stimulus properties of delta9-THC and psilocybin in rats.

Male albino rats were trained to respond differentially on the left or right lever in a 2-lever chamber on the basis of which drug had been given intra-peritoneally (IP) 30 min before experimentation. In 1 group 1.9 mg/kg of delta9-THC and control injections (vehicle) served as the discriminative stimuli associated with each lever and in another group the drug stimuli were 1.0 mg/kg of delta9-THC and 1.0 mg/kg of psilocybin. The results confirmed those of other experiments using different procedures; that delta9-THC can acquire discriminative control over responding. The fact that delta9-THC and psilocybin were also found to differentially control lever choice demonstrates that these 2 drugs probably produce discriminably different states in rats.

Animals↗
PubMed2006

Carbachol injections into the nucleus accumbens disrupt acquisition and expression of fear-potentiated startle and freezing in rats.

The nucleus accumbens is involved in different types of emotional learning, ranging from appetitive instrumental learning to Pavlovian fear conditioning. In previous studies, we found that temporary inactivation of the nucleus accumbens blocked both the acquisition and expression of conditioned fear. This was not due to altered dopaminergic activity as we have also found that intra-nucleus accumbens infusions of the dopamine agonist amphetamine do not affect either the acquisition or the expression of conditioned fear. Therefore, in the present study we examined whether cholinergic activity in the nucleus accumbens is involved in the acquisition and expression of conditioned fear. Specifically, the effect of intra-nucleus accumbens infusions of the unselective cholinergic agonist carbachol on the acquisition and expression of conditioned fear was assessed. Across several experiments, we measured fear to visual and acoustic conditioned stimuli and to the experimental context. Further, two different measures of conditioned fear were recorded: fear potentiation of startle and freezing. Intra-nucleus accumbens carbachol infusions disrupted acquisition as well as expression of conditioned fear, regardless of the modality of the fear-eliciting stimulus or of the specific measure of conditioned fear. This disruption of conditioned fear was not simply a by-product of enhanced motor activity which also occurred after intra-nucleus accumbens carbachol infusions. Interestingly, despite the substantial effect of intra-nucleus accumbens carbachol on expression of conditioned fear, the results of the final experiment suggest that these rats extinguish similarly to control rats. Taken together, the present results indicate that acetylcholine within the nucleus accumbens is important for the learning and retrieval of conditioned fear.

Acetylcholine↗