Pre-training Injection Research Articles

Effect of pimozide on the improvement in learning produced by self-stimulation and by water reinforcement

When rats self-stimulate immediately after the training trial of an appetitive task their performance on a retention test is improved the next day. In the present study, this improvement was blocked by pretraining injections of pimozide, a dopaminergic blocker. In a second experiment, injections of pimozide retarded learning on the same task when the learning was reinforced by drinking water, but had no effect on learning which occurred in the absence of a reinforcer. The data made the hypotheses that the animal's behavior was a result of an action of pimozide on sensory or motor mechanisms, or that the drug produced state-dependent effects, highly unlikely. We concluded that neural systems involving dopamine mediate an effect of reinforcing events on behavior.

Role of biogenic amines in the reversal of cycloheximide-induced amnesia.

Amnesia was induced by pretraining injections of cycloheximide (CYC) in a food motivated discrimination reversal task. Magnitude of amnesia varied as a function of the amount of training on both the initial discrimination and the reversal and also as a function of the length of intertrial interval used on both the reversal and the test. Memory spontaneously recovered 48 hr. following reversal training. Recovery from amnesia was induced by pretesting injections of d-amphetamine and 2 monoamine oxidase inhibitors, pargyline and catron. This enhanced performance was a true recovery of the memory and not a result of enhanced learning or increased arousal. Depletion of catecholamines by alpha-methyl-para-tyrosine, a tyrosine hydroxylase inhibitor, and diethyldithiocarbamate, a dopamine beta hydroxylase inhbitor, resulted in an amnesia quantitatively and qualitatively similar to amnesia induced by CYC. These data support the hypothesis that CYC-induced amnesia is mediated via central catecholamines.

Recovery from amnesia induced by pre-test injections of monoamine oxidase inhibitors

Amnesia was induced in C57BL6J male mice by pre-training injections of cycloheximide (CYC) in a one-trial passive avoidance task. This amnesia was reversed by pre-testing injections of two monoamine oxidase inhibitors (MAOI's) catron and pargyline. The results of 2 non-contingent control groups indicated that mice injected with cycloheximide but given foot shock in a place different from the training apparatus did not show increased latency following treatment with catron and pargyline. This indicates that recovery is specific for training in the passive avoidance task. Depletion of norepinephrine (NE) by diethyldithiocarbamate (DEDTC), a dopamine beta hydroxylase inhibitor, resulted in an amnesia similar to that induced by CYC. DEDTC-induced amnesia was also reversed by catron and pargyline.

Comparison of the effects of anisomycin on memory across six strains of mice

Retention for step-through passive avoidance training was compared across six strains of mice including pigmented and albinos, inbred and outbred, and strains light and heavy in weight. Widely differing conditions of training were required in order for 90–100% of the mice in each strain to learn one-trial passive avoidance. The effect of anisomycin on protein synthesis was investigated and no major differences were found across strains. A single injection of anisomycin, given 15 min prior to training, was found to cause significant amnesia for passive avoidance training in all strains of mice. It was also found that a small increase in shock intensity decreased the percent amnesia caused by a single pretraining injection of anisomycin. If at this higher shock intensity the pretraining injection was followed by a second injection of anisomycin, given 1.75 hr after training, a high percentage of the subjects was again found to have amnesia. Discussion includes (a) possible causes of strain differences in ability to acquire the passive avoidance habit, (b) a general methodology for obtaining amnestic effects independent of the particular strain of mice used, and (c) the necessity of protein synthesis for memory formation.

Influence of training strength on amnesia induced by pretraining injections of cycloheximide

Cycloheximide-treated mice and saline controls were given one-trial training in a black and white, step-through, passive avoidance box. The following parameters were shown to affect the degree of amnesia in cycloheximide-treated animals: (a) shock intensity; (b) shock duration; (c) original latency to enter the shock compartment; and, (d) retention interval (periods used were 24 hr and 1, 2, and 3 weeks). When those parameters are measured and controlled, highly consistent amnestic effects can be obtained. In the present experiment, certain groups showed over 80% amnesia while the controls showed less than 2% amnesia. Amnesia could best be obtained in passive avoidance when animals were trained to just under the asymptote of the acquisition curve. Measures of inhibition of protein synthesis by cycloheximide showed differences among 5 strains, but there were no significant individual differences within a strain.