Brain phosphoproteins: the effect of short experiences on the phosphorylation of nuclear proteins of rat brain

The cAMP cascade in the nervous system: molecular sites of action and possible relevance to neuronal plasticity

Many intercellular messages regulate the activity of their target cells by altering the intracellular level of cAMP and, as a consequence, the phosphorylation state of proteins which serve as substrates for cAMP-dependent protein kinase. Such regulation plays a crucial role in neuronal development, neuronal function, and neuronal plasticity (e.g., elementary learning mechanisms). Ample information has been accumulated in recent years on the enzymes that regulate the level of cAMP or respond to it, on the regulation of cAMP synthesis by neurohormones, neurotransmitters, ions, and toxins, on neuronal-specific substrate proteins that are phosphorylated by the cAMP-dependent kinase, and on the interaction of the cAMP-cascade with other second-messenger systems within neurons. Such data, obtained by a combination of molecular-biological, biochemical, and cellular approaches, shed light on the detailed mechanisms by which modulation of a ubiquitous molecular cascade leads to a great variety of short-term as well as long-term specific neuronal responses and alterations.

Adenosine-3,5-phosphate levels in brain structures of rats submitted to four different behavioral procedures

Shuttle avoidance training decreased the cAMP content of rat brain (excluding hippocampus and caudate nucleus), amygdala and hypothalamus. Stimulation by tones alone had a similar effect, but only in the brain fraction. Pseudoconditioning or footshocks alone had no effect.

Effect of various forms of training and stimulation on the incorporation of 32P into the nuclear phosphoproteins of the rat brain

Incorporation of 32P into acid-extractable nuclear proteins was measured in the hippocampus, caudate nucleus, rest of the brain, and liver of rats submitted to various different behavioral treatments in a shuttle-box. After 5 min of classical conditioning, of avoidance without CS-US pairing, and of avoidance with CS-US pairing (standard shuttle avoidance), there was an increased 32P uptake by acid-extractable nuclear proteins in the hippocampus and caudate nucleus. The effect disappeared between 5 and 25 min of training. After 25 min of buzzers alone, or of footshocks alone, a similar 32P uptake change was noted in the same brain structure, which raises doubts as to the specificity of the phenomenon in terms of learning mechanisms.

Effects of a novel experience on rat brain chromatin

In this study adult Fischer, inbred rats experienced (1) training to avoid footshock (2) unavoidable footshock or (3) no training or footshock. Each animal was sacrificed at one of several time points (1-60 hours) following experience. Brain chromatin was extracted and used as template for RNA synthesis in vitro. Both groups which received the novel experience demonstrated greater template activity than the unshocked, untrained groups. This effect was brief. The two groups which received the experience did not differ from each other. These results suggest that a brief, novel experience can temporarily alter the transcriptional activity of brain chromatin.

Stimulation increases incorporation of [3H]lysine into rat brain and liver proteins

Exposure of rats to electric footshocks or merely to the footshock apparatus increased the incorporation of [3H]lysine into brain and liver protein. The effect was present in both fore-and hindbrain. The footshock treatment was the more effective stimulus, producing larger and more significant changes. These results resemble those previously observed in C57Bl/6J mice, and thus suggest that altered protein or amino acid metabolism is a general response to stress in rodents.

Brain protein metabolism and the acquisition of new behaviors. II. Immunological studies of the alpha, beta and gamma proteins of goldfish brain

In a previous study, the labeling pattern of three proteins (alpha, beta and gamma) in goldfish brain was found to change after the animals successfully acquired a new pattern of behavior. In the present study, these proteins were isolated from the brain cytoplasmic fraction, purified by successive gel electrophoresis and used as antigent to immunize rabbits. Antisera containing antibodies to two of the proteins (beta and gamma) were obtained. These gave single precipitin bands when plated against the antigens and a mixture of the total cytoplasmic proteins. The distribution of beta and gamma in brain subcellular fractions and in a variety of goldfish tissues was determined by immunodiffusion methods. gamma was specific to brain. The beta protein cross-reacted but was not identical to a widely distributed substance in plasma, liver and kidney. Both beta and gamma appear to be species specific in that no cross-reactivity was obtained with mouse, chick or rat brain proteins. Immunological methods, in combination with double labeling experiments were used to establish that the beta and gamma antigens were proteins which were normally present in goldfish brain. Both the beta and gamma antisera were equally capable of specifically precipitating the proteins which were differentially labeled after training as well as purified proteins of the same molecular weight present in the brains of control animals. These results suggest that the acquisition of a new pattern of behavior can increase the demand for the synthesis of specific proteins (beta and gamma) normally present in goldfish brain.

Experiential input alters the phosphorylation of specific proteins in brain membranes

The effects of a training experience that involves foot shock on the endogenous phosphorylation of membrane-bound proteins from brain were studied. Crude membrane fractions were prepared from the cerebral cortex and neostriatum of animals that had been sacrificed by quick freezing. In vitro incubation of the membranes with gamma-32P-ATP, follwed by SDS-gel electrophoresis of the phosphorylated substrates, revealed that the phosphorylation of two protein components (designated F and H-I) increased in preparations from animals that were subjected to a training experience 24 hr prior to sacrifice. These effects were greater in preparations from the neostriatum than from the cerebral cortex, and were observed in experiments using both rats and mice. Although all trained animals showed a high phosphorylation of bands F and H-I, control animals showed a greater variability in the phosphorylation of these bands. The results indicate that the phosphorylation of specific proteins may play a mediatory role in the processing of experiential information.

Identification of specific changes in the pattern of brain protein synthesis after training

Double labeling studies with [3H]valine and [14C]valine were used to investigate the pattern of protein synthesis in the brains of goldfish. The protein fractions in three bands (alpha, beta, and gamma) on sodium dodecyl sulfate-polyacrylamide gels indicate that more valine was incorporated in the brains of goldfish that had been trained in a vestibular conditioning task than in the brains of untrained fish or fish trained in a variety of control behavioral situation. Changes in the pattern of labeling were localized in the cytoplasmic fraction of the brain; no increases in labeling occurred in either the nuclear or synaptosomal components. The results suggest that a specific change occurs in the pattern of protein synthesis in the brain after the acquistion of a new behavior.

Brain metabolism and the acquisition of new behaviors. I. Evidence for specific changes in the pattern of protein synthesis

The pattern of incorporation of labeled valine into goldfish brain proteins was compared for animals trained in a new swimming skill with controls. Double labeling studies followed by electrophoretic separation of the proteins on SDS-polyacrylamide gels, showed that there was a consistent increase of valine incorporation for the trained animals at 3 band positions on the gels. These alpha, beta, andnu bands correspond to molecular weights of 37,000, 32,000 and 26,000 daltons. The protein changes were confined to the brain cytoplasmic fraction, in that they were absent from the brain nuclear, brain synaptosomal, and kidney cytoplasmic proteins. Such protein changes were not obtained for a variety of control behavioral situations. The results suggest that there is higher rate of synthesis of specific proteins in goldfish brain following the acquisition of a new pattern of behavior.