Some effects of injections of ribonucleic acid

Abstract

Yeast ribonucleic acid (RNA) was first mentioned as having beneficial effects on memory by Cameron and co-workers (1961, 1963) who reported that RNA administered in tablet form or by intravenous injection produced clinical improvement in patients suffering from senile memory impairmenL This effect was later studied by Cook et al (1963) who showed that yeast RNA (160 mg/kg I.P.) increased the rate at which rats learn the response of climbing a pole to escape shock. Recently, however, the suggestion that RNA produces a general improvement in learning or memory processes has been questioned by Wagner et al (1966). These workers repeated the experiment reported by Cooketal and obtained essentially the same results. They then went on to test the effects of yeast RNA injections on learning of a food motivated brightness discrimination, on shock sensitivity and on general activity and found that RNA did not change performance in these situations. Similarly, Luttges et al (1966) have shown that rats injected with rat brain RNA were not superior to a saline injected control group in various learning situations, including a water "Y" maze and a Lashley III maze.Luttges et al also found that IP injections of p32 labeled RNA did not result in significant amounts of radioactivity being found in the brain. This result has also been obtained by Sved (1965), and by Eist & Seal (1965) using a tracer technique, and by Enesco (1966), using radioautography, and suggests that any effects of exogenous RNA are not due to a direct incorporation of RNA into brain tissue.The present study was undertaken in an attempt to determine the basis of the effect of RNA injections on shock motivated pole-climbing behavior and to examine the effects of these injections on behavior in other situations. The Ss were required to learn a spatial discrimination and reversal in an electrified two-choice discrimination box which was divided into five sections: start area, choice area, two threshold areas and a goal area. All but the goal area had grid floors which could be electrified by the experimenter. A detailed description of the apparatus and technique has been given elsewhere (Corson, 1965). On the first training day the Ss learned to go quickly from the start to the goal (the start grid was electrified at 5 sec. and all grids were electrified at 30 sec.), through either door, to avoid shock. Having reached a criterion of three consecutive unshocked runs, they then learned to enter the goal by crossing the threshold area on one side. During this phase the incorrect door was locked and its threshold area was electrified. On the following day, the 0ppcsite door was correct.The results show that neither of the experimental groups was different from the controls in any of the measures taken (start latency, total latency, number of trials to criterion in each phase, and number of errors in each phase). The Mann-Whitney U test (two-tailed) was used in all cases.It is important to note that the first phase of this experiment, when the animals had not yet ...

Effect of magnesium pemoline on learning and memory of a one-way avoidance response

“…Cook et al (1963) found that injections of yeast RNA caused rats to learn to pole-climb to avoid shock faster than control animals. However, Corson & Enesco (1966), although able to replicate these results with poleclimbing, were unable to obtain increased learning rates using an escape task which required animals to run down an alley to a goal box. Evidently the generality of the results of Cook et al (1963) is limited since they apply to a pole-climbing avoidance response, but not to a running avoidance response.…”

“…This is suggested by the relationship between the studies of Cook et al (1963) and Corson & Enesco (1966). There are, of course, many other possible causes.…”

“Transfer of learning” by injection of brain RNA: A replication

“…Recipient groups received the two kinds of RNA extract via intraperitoneal injection. The group injected with the extract from the brains of the conditioned animals showed significantly greater avoidance of the preferred chamber.Recent research has reported beneficial effects on memory due to ribonucleic acid (RNA) administration (Cameron & Solyom, 1961; Cameron et aI, 1963;Cook et al, 1963;Wagner et al, 1966;Corson & Enesco, 1966). There have also been reports of "transfer" effects accomplished through RNA extraction from the brains of trained animals and its injection into naive animals (Babich et aI, 1965;Jacobson et al 1965; Fjerdingstad et al, 1965).…”

Comment on Solyom, Beaulieu and Enesco

“…Evidence that RNA treatments produce no changes in open field activity has no bearing on this problem. In fact, Corson & Enesco (1966) report RNA to produce changes in instrumental performance that do not arise from the learning process. An additional group of animals trained under RNA but extinguished without RNA would establish the importance of RNA per se on rate of extinction.…”

“…Many drugs (amphetamine, caffeine) enhance the tendency to respond but have no effects on learning (e.g., Weiss & Laties, 1962). Crucial information about effects on learning could be gotten by continued testing after RNA injections have ceased.Finally, the extinction data show that animals responding at a high baseline rate generate extinction curves differing slightly from those with a lower Corson & Enesco (1966) report RNA to produce changes in instrumental performance that do not arise from the learning process. An additional group of animals trained under RNA but extinguished without RNA would establish the importance of RNA per se on rate of extinction.…”