Cellular Connections Revealed by Transneuronal Transport of HRP in the Guinea Pig Cochlear Nucleus

Abstract

The technique of intracellular injection of horseradish peroxidase (HRP) has been successfully used by a number of workers in order to label physiologically characterised cells in the cochlear nucleus (e.g. Rhode et al., 1983a, b; Rouiller and Ryugo, 1984, in the cat). We have extended it to the guinea pig cochlear nucleus (Parker et al., 1987). In addition to permitting a correlation between cell morphology and physiological response characteristics, this technique has conveniently resulted in transneuronal transport of HRP. Transneuronal transport of HRP, well described in other systems, is the process by which HRP in the injected cell gains access to other neurones, whether or not their synaptic contacts are involved. The process is facilitated by a number of factors; e.g. a large injection of HRP into the cell, adequate physiological condition of the animal (and, therefore, of the donor and recipient cells), a long post-injection survival time (Nassel, 1981), and increased activity of the neurones involved by appropriate stimulation (Harrison et al., 1984). This communication describes the physiological characterisation and HRP-labelling of a single giant (large multipdlar) cell, the soma of which was situated in the guinea pig anteroventral cochlear nucleus (AVCN) , and the transneuronal transport of HRP from this cell into a variety of different cell types in the cochlear nucleus. A preliminary communication of these data has been made (parker et al., 1986).