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The distribution of glutamic acid decarboxylase (GAD)-like immunoreactivity in the lateral geniculate nucleus (LGN) of the human adult was studied in vibratome sections (50–60 urn thick) using the avidinbiotin-peroxidase method. The tissue was obtained at autopsy from five individuals without any known neurological disorders. Only few GAD-immunoreactive neurons were present in the layers of the LGN, even less in the interlaminar zones. The numerical density of GAD-immunoreactive neurons and puncta (probably synaptic boutons and/or cross sectioned cell processes) in the magnocellular layers was larger than in the parvocellular layers. Furthermore, no striking differences between the individual parvocellular layers were noted. The immunoreactive somata were polygonal or triangular, occasionally pear-shaped, and ranged in size from 15 to 25 urn. They gave off two to four short, thick, straight primary dendrites. A preferred orientation of dendrites was not recognized. After bleaching the chromogen 4-chloro-1-naphthol and staining for lipofuscin pigment granules and basophilic material, 254 unequivocally relocated GAD-immunoreactive nerve cells could be classified as belonging to the lipofuscin pigment granules-containing class of interneurons.

Tritiated 9'-nor-fusicoccin-8'-alcohol provides a highly bioactive radioligand of high specific activity which is easily prepared by oxidation of fusicoccin and subsequent reduction with tritiated sodium borohydride. Using this radioligand, we have identified and characterized a selective binding site for fusicoccin (Ka for [3H]-9'-nor-fusicoccin-8'-alcohol=0.20·109 M-1; Ka, apparent for fusicoccin=0.21·109 M-1) located at the plasmalemma of Vicia faba leaf tissue. The site is thermolabile, readily degraded by trypsin and located at the apoplastic face of the plasmalemma based on results obtained using right-side-out plasmalemma vesicles prepared by aqueous two-phase partitioning and macromolecular fusicoccin-derivatives. The binding-protein is present in guard cells of Vicia faba, as shown by the use of purified guard-cell protoplasts.