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Unique RNA species developed during a shock avoidance task
Abstract
A DNA-RNA successive competition experiment in which DNA is hybridized first with brain RNA from rats subjected to forced motor activity and then with brain RNA from shock avoidance trained rats suggests that unique RNA species are synthesized during this latter task.
... However, this activation cannot be proved direct1y. Direct proof of the activation of DNA is possible, e_g., by hybridization methods (e.g., Machlus & Gaito, 1968). However, we suppose that indirect methods may also present suitable results. ...
The effect of 0.5-M hydroxylamine injected intracranially on a passive-avoidance task was followed in mice. Hydroxylamine administered 24 h before the acquisition trial or earlier had no effect on performance of animals. Hydroxylamine injected 2 h before the acquisition trial impaired the performance of animals tested 24, 48, 72 h, or 1 week later. Hydroxylamine injected 1, 2, or 24 h later interfered with the performance of animals, too. The later hydroxylamine was injected, the later the impairment of performance of animals appeared. The effect of hydroxylamine is probably associated with the “mutagenic” action of the drug on activated DNA.
Bowman and Strobel [5] reported increased incorporation of tritiated cytidine into hippocampal RNA of rats learning 60 min of repeated spatial reversals for water reinforcement in an automated Y-maze. The present studies replicated this effect 3 times using intravenous (IV) injections of tritiated cytidine, but failed to observe such an effect in 3 other replications using intracranial (IC) injections of tritiated cytidine. Various control conditions appear to rule out injection trauma as a reason for the lauter failure. The observation of equal precursor distribution across brain regions following IV injections and of unequal distribution following IC injections, coupled with the autoradiographic observations of Altman and Chorover [1] of steep hypothalamic distribution gradients of IC injected nucleoside in the cat, indicate that regional metabolic measurements following IC injections of precursors do not equally assess the contributions of all brain cells and can lead to serious quantitative errors. This point needs reemphasis in view of the widespread use of IC injections in psychoneurochemical research. Concerning the possibility of stress or corticosterone effect on the observed hippocampal RNA effect, there were no differences found in plasma corticosterone concentrations between the learning and control rats at sacrifice.
Operant schedules were used to isolate component parts of a training task and specific activities were determine for nuclear and cytoplasmic RNA species separated by polyacrylamide disc gel electrophoresis. Rats exposed to a stimulus or schedule change incorporated more radioactivity into nuclear rRNA and mRNA and cytoplasmic rRNA and tRNA than littermates exposed to no change from baseline training. Rats developing a change in response probability to a stimulus in the environment incorporated more radioactivity into cytoplasmic mRNA.
The literature on the possible role of RNA and protein in long-term memory is reviewed in terms of the following five criteria: (1) The molecule should have a defined role in normal brain function. (2) There should be a quantitative and/or qualitative change in the molecule as a function of learning. (3) The molecule should lead to some type of relatively permanent change in the functioning of the brain. (4) Altered synthesis or utilization of the molecule should lead to predictable consequences for memory. (5) The localization of the response should be consistent in terms of the utilization of that portion of the brain in the particular task.
Acknowledges W. Greenough and S. Maier's (see PA, Vol. 49:Issue 5) assertion concerning the problem of adequate controls in molecular psychobiological research. 3 methodological possibilities that attempt to handle this aspect are discussed.
Reviews research purporting to demonstrate the occurrence of quantitative or qualitative changes in RNA and/or protein during simple and complex behavior. Limitations in interpretation of research results and methodological problems are discussed. Much research indicates that quantitative changes do occur. Generally, increments tend to result with mild or moderate stimulation; decrements, with drastic or prolonged stimulation. However, there is no conclusive evidence to indicate that qualitatively different RNA and/or protein species are synthesized during behavior. The necessity for research involving methods sensitive to the detection of qualitative changes is suggested. (4 p. ref.)
A DNA-RNA successive competition experiment in which DNA is hybridized first with RNA from nonbehaving rats and then with RNA from shock avoidance trained rats suggests that unique RNA species are synthesized during this task.
An improved method for the formation of DNA—RNA hybrids is described. The procedure involves immobilizing denatured DNA on nitrocellulose membrane filters, hybridizing complementary RNA to the membrane-fixed DNA, and eliminating RNA “noise”. Denatured DNA and hybridized RNA remain on the filter throughout the procedure. Unpaired RNA is removed by washing, and RNA complexed over short regions is eliminated by RNase treatment.Many samples can be easily handled, permitting kinetic and saturation studies. Large amounts-of DNA can be loaded on a filter without interfering with the efficiency of the annealing reaction. Moreover, the “noise” can be depressed to a level (0·003% of the input RNA) permitting the identification of small regions of DNA complementary to a given RNA species. The results are quantitatively more certain than annealing in liquid, since the competing DNA renaturation reaction is suppressed.
Detection of RNA species unique to a behavioral task NOTE I. This research was supported by Office of Naval Research Contract Nom 4935(00) and Grant No
- B Gaito
MACHLUS, B.• & GAITO, J. Detection of RNA species unique to a
behavioral task. Psychon. Sci. 1968, 10,253-254.
NOTE
I. This research was supported by Office of Naval Research Contract Nom
4935(00) and Grant No. APA-I22 from the National Research Council of
Canada.