Ultrastructural relationship between N-methyl-D-aspartate-NR1 receptor subunit and mu-opioid receptor in the mouse central nucleus of the amygdala.

The central nucleus of the amygdala (CeA) is an important neuroanatomical substrate of emotional processes that are critically involved in addictive behaviors. Glutamate and opioid systems in the CeA play significant roles in neural plasticity and addictive processes, however the cellular sites of interaction between agonists of N-methyl-d-aspartate (NMDA) and mu-opioid receptors (muOR) in the CeA are unknown. Dual labeling immunocytochemistry was used to determine the ultrastructural relationship between the essential NMDA-NR1 receptor subunit and muOR in the CeA. It was found that over 80% of NR1-labeled profiles were dendrites while less than 10% were axons. In the case of muOR-labeled profiles, approximately 60% were dendritic, and over 35% were axons. Despite their somewhat distinctive patterns of cellular location, numerous dual-labeled profiles were observed. Approximately 80% of these were dendritic, and less than 10% were axonal. Moreover, many dual-labeled dendritic profiles were contacted by axon terminals receiving asymmetric-type synapses indicative of excitatory signaling. These results indicate that NMDA and muORs are strategically localized in dendrites, including those receiving excitatory synapses, of central amygdala neurons. Thus, postsynaptic co-modulation of central amygdala neurons may be a key cellular substrate mediating glutamate and opioid interaction on neural signaling and plasticity associated with normal and pathological emotional processes associated with addictive behaviors.

New assay for the rapid determination of plasma holotranscobalamin II levels: preliminary evaluation in cancer patients.

We describe a new and rapid assay for the measurement of plasma B12 bound to transcobalamin II (holotranscobalamin II) using the property of adsorption of the polypeptides of apotranscobalamin II and holotranscobalamin II to the hydrophobic surface of microfine glass particles. Acid-washed microfine glass was used to separate vitamin B12 bound to the glycoproteins transcobalamin I and transcobalamin III (haptocorrin or R binder) from that bound to transcobalamin II. Sephadex gel filtration separation of 57Co-labelled vitamin B12 binders confirmed that > 90% of holotranscobalamin II can be removed from plasma holohaptocorrin by adsorption to microfine glass particles. Since only holotranscobalamin II is capable of delivering vitamin B12 to metabolizing cells, plasma holotranscobalamin II content reflects the availability of B12 to cells. Use of this test in cancer patients undergoing either chemotherapy or radiation therapy revealed evidence of early negative B12 balance that in some instances was induced by the treatment itself.