Diversity of mRNAs in the Axonal Compartment of Peptidergic Neurons in the Rat

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Abstract
Vasopressin and oxytocin mRNAs, which are normally translated in the perikarya of magnocellular neurons, have recently been demonstrated to be also present in axons and nerve terminals which are located in the posterior pituitary. The physiological significance of this observation has not yet been resolved. In order to gain further insight into the function and plasticity of the peptidergic neuron the question was addressed whether axonal localization is a unique feature of the above-mentioned transcripts. Biochemical evidence is presented that magnocellular axons and nerve terminals also contain mRNA species encoding a member of the neurofilament protein family and the prodynorphin precursor. These data imply that axons may harbour a variety of additional protein-encoding transcripts. Furthermore, it is shown that in the mutant (Brattleboro) rat, which lacks detectable levels of vasopressin but which still transcribes the corresponding gene, axonal vasopressin but not oxytocin mRNA contents are dramatically reduced. Most likely, vasopressin transcripts are absent from the nerve terminals as a consequence of the impaired precursor biosynthesis in the cytoplasm of the mutant rat.