CPEB-mediated cytoplasmic polyadenylation and the regulation of experience-dependent translation of alpha-CaMKII mRNA at synapses

Long-term changes in synaptic efficacy may require the regulated translation of dendritic mRNAs. While the basis of such regulation is unknown, it seemed possible that some features of translational control in development could be recapitulated in neurons. Polyadenylation-induced translation of oocyte mRNAs requires the cis-acting CPE sequence and the CPE-binding protein CPEB. CPEB is also present in the dendritic layers of the hippocampus, at synapses in cultured neurons, and in postsynaptic densities of adult brain. alpha-CaMKII mRNA, which is localized in dendrites and is necessary for synaptic plasticity and LTP, contains two CPEs. These CPEs are bound by CPEB and mediate polyadenylation-induced translation in injected Xenopus oocytes. In the intact brain, visual experience induces alpha-CaMKII mRNA polyadenylation and translation, suggesting that this process likely occurs at synapses.

Behavioral correlates of hippocampal type 2 theta in the rat

Previous research has indicated that there are two types of theta activity which can be recorded from the hippocampus in most rodents. One type (type 1) of theta is correlated with voluntary movements while the second (type 2) occurs during immobility. A third waveform termed LIA (Large Amplitude Irregular Activity) occurs during more automatic behaviors, e.g., grooming, shivering or immobility. In the rabbit and guinea pig type 2 theta can readily be elicited in unrestrained animals. However, type 2 theta is rarely seen in the unrestrained rat. The purpose of the present study was to determine the stimulus conditions that are necessary for the elicitation of type 2 theta in the rat. In the present study 20 unrestrained rats were observed in the presence of a cat or a ferret. Movements by the cat or ferret produced theta in immobile rats. Sensory stimuli which did not ordinarily produce type 2 theta would reliably do so in the presence of the cat or ferret. It is hypothesized that type 2 theta in the unrestrained immobile rat occurs during sensory processing but only when the animal is in a high state of "arousal."