Mesencephalic central gray lesions and fear-motivated behavior in rats

Aftetr one-trial passive-avoidance training, indepelenet groups of rats tested promptly after training or at successive 6-hour intervals displayed a repetitive pattern of high then low retention scores. These results suggest that some physiological rhythm may interact with retention performance.

https://science.sciencemag.org/content/sci/180/4082/208.full.pdf

Multiphasic retention deficits at periodic intervals after passive-avoidance learning.

Time-dependent variations in aversively motivated behaviors: nonassociative effects of cholinergic and catecholaminergic activity.

These experiments explored whether exposure to inescapable shock produces a subsequent deficit in the organism's propensity to associate its behavior with shock termination. Previous experiments are incapable of resolving this question because they confound reduced associability and decreased activity. Four experiments examined the effects of inescapable shock on the acquisition of Y-maze escape. Here, escape is accomplished by choosing the correct response from two available alternatives rather than by simple locomotion as in a shuttle box. By itself, reduced activity should not produce inaccurate choices, only slow choices. Experiment 1 found that inescapable shock produced slow learning of the correct choice for escape, even though active choices occurred on every trial. Further, the speed and accuracy of choice were not correlated. The second experiment showed that the choice escape learning deficit was produced by the inescapability of the shocks. Experiment 3 demonstrated that the choice accuracy of inescapably shocked rats was not improved by increases in Y-maze shock intensity, even though speed of responding was increased. The final experiment revealed that the effects of inescapable shock on Y-maze acquisition did not dissipate across a 1-wk period.

Learned helplessness, inactivity, and associative deficits: Effects of inescapable shock on response choice escape learning

The reinforcing properties of ethanol were examined in naive adult male rats by means of a place conditioning paradigm that has previously demonstrated the positive reinforcing properties of food, water and some drugs, and the aversive properties of punishers such as electric shock and lithium chloride. Only doses of 0.8–1.0 g/kg and higher produced clear place conditioning, and this was only conditioned place aversion; rats spent significantly more time on the side of the place conditioning box in which they received the vehicle than on the side in which they received ethanol. Doses between 0.1 g/kg and 0.8 g/kg produced increases in general activity, but did not produce any place conditioning. Control experiments indicated that the pattern of effects was not specific to the route of ethanol administration (intravenous or intragastric), rate of infusion, concentration, or vehicle. It was concluded that ethanol, in the doses used here, has only punishing or neutral motivational effects in naive rats and does not serve as a primary positive reinforcer in this model. The conclusions are discussed in relation to the relative difficulty encountered in attempts to produce ethanol self-administration, and the findings are viewed as consistent with a proposal that prolonged training and experience with ethanol are important for ethanol self-administration by the rat.

Kumar R

Papers

Incubation of fear: experiments of the "Kamin Effect" in rats.