Effects of conditioned avoidance training on polyribosomes of mouse brain

Role of RNA and protein synthesis in memory formation

A brief review is given of experiments which are concerned with the hypothesis that brain RNA and protein synthesis are directly involved in the establishment of long-term memory. It is concluded that these experiments neither support or refute this hypothesis. A convincing demonstration is lacking of interanimal memory transfer by injection of macromolecular extracts. The majority of experiments which attempt to correlate increased macromolecular synthesis with learning use radioactive precursor methods and these studies do not exclude possible changes in precursor specific activity as the cause of the increased labeling. Although some studies find directly observable changes in brain macromolecules in response to training, their relationship to memory formation is unclear. It is possible that these changes represent only an enhanced production of constitutive macromolecules in response to an increase in cerebral metabolism during training, rather than molecular changes that are directly involved with modifying synaptic connectivity. Inhibitors of cerebral protein synthesis block memory formation, but these drugs are not pharmacologically specific and this complicates the interpretation of these studies.

Biologic correlates of psychoanalytic concepts

In deference to Freud's ingenious predictions of the future potential of the biological sciences concerning psychoanalytic tenets and clinical disorders, an attempt is made to bring the concepts of the Three Polarities, life and death instincts, the Unconscious, and repression into association with relevant anatomical, neurophysiological, and neurochemical data. Implications for diagnosis and therapy were considered in the light of recent and anticipated neurobiological advances. Building bridges between biologic and physiologic processes is exceedingly complicated by the enormous complexities of both fields. There is good reason to hope that the speculative nature which at this time pervades our bridging efforts will eventually be substituted by unequivocal facts and deductions.

Effect of sensory stimulation on the uptake and incorporation of radioactive lysine into protein of mouse brain and liver

Alterations in incorporation of tritiated lysine into protein of mouse brain and liver were observed following brief exposure to a variety of sensory stimuli. During a 15-min session, subjects were trained to perform a one-way active avoidance response or else were exposed to one of the stimulus components of the situation, including shocks, buzzers, lights, handling, and the apparatus alone. Twenty min after these behavioral treatments, tritiated lysine was injected subcutaneously, and its incorporation into total protein during a 10-min pulse was measured. Quiet mice, undisturbed until injection of the precursor, constituted the baseline group for biochemical comparisons. Most behavioral treatments increased the total amount of radioactivity in brain and liver. The treatments increased the incorporation of radioactivity into protein of both organs even more, thereby producing elevations of relative radioactivity (RR) of protein, a measure of the amount of radioactivity incorporated into protein relative to that in the acid-soluble pools. The RR increases following most of the behavioral experiences were approximately equal; however, exposure to lights or to the apparatus were less effective than the other treatments in eliciting these metabolic changes. The responses were greatly diminished in mice previously exposed to the treatments. Thus, the effectiveness of a stimulus in producing these metabolic alterations may depend upon its apparent magnitude and its novelty. The total radioactivity increases were larger in brain than in liver, while the RR increases were smaller in brain than in liver. Brain RR increases were of equal magnitude when the precursor was injected 5, 20, or 35 min after behavioral treatment, whereas the liver RR responses declined markedly over this period. Despite these differences, strong positive correlations between brain and liver across the various behavioral treatments existed. The RR changes occurred about equally in the cerebellum-brain stem, basal ganglia, hippocampus-septum, and ventral cortex, while the thalamus-hypothalamus and dorsal cortex showed smaller differences.