While recent studies have established the presence of voltage-gated ion channels on Schwann cells in culture and on freshly isolated fibers from mature mammals, an important issue not yet explored is whether Schwann cell channels are regionally specialized. In the nodal region, the intimate association between the Schwann cell and its axon suggests that this is a likely site for functional specialization. Here, we examine whether there is a localized expression of channels in the Schwann cell paranodal regions, in a manner similar to that already shown for the nodal axon. Cell-attached and outside-out patch-clamp recordings were made from paranodal regions of rat myelinated sciatic nerve fibers where the myelin on both sides of the node was retracted by enzymatic treatment. Even though no myelin was visible on the surface of the retracted paranode, significant portions of this surface were found to stain positively with a marker (anti-galactocerebroside) for Schwann cell membranes, suggesting that part of the axon still was covered by glial membranes. Using Lucifer yellow in the recording pipettes, we observed that the dye diffused into either axons or Schwann cells when the membrane under the tip was ruptured. Using this as a criterion to identify membranes obtained from retracted paranodes, we found delayed and inwardly rectifying potassium channels on both axon- and Schwann-derived patches. However, sodium channels were detected only in axon patches. This is the first report that voltage- gated glial channels are present in immediate vicinity to axons of the PNS. This finding, coupled with earlier reports that functional channels are absent in soma of mature myelinating Schwann cells, suggests that ion channels in these cells are regionally specialized for functional interaction with axons.

Social facilitation of feeding in domestic chicks has been attributed to emotion reduction accompanying social stimuli. In order to test the hypothesis that this emotion reduction is due to socially-raised chicks being imprinted to one another, 3 groups of domestic chicks were imprinted, reared in isolation, or reared in a group. The number of food pecks made in a novel testing area were recorded when each S was alone, with the imprinting object, or with a food-deprived chick. The test condition similar to each group's early experience produced the greatest eating for that group at 6-hr, deprivation, but not 3-hr, deprivation.

The concept and product reported here have potential to provide dairy farmers with a practical means to prevent hypocalcaemia and improve milk production during early lactation.

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