Use of Excitatory Amino Acids to Make Axon-Sparing Lesions of Hypothalamus

Publisher Summary This chapter describes the methods that have proved to be useful in the laboratory for injecting excitatory amino acids into discrete brain regions of rodents and for determining the extent of the resulting lesions. The chapter first presents the injection procedure. Because of its great potency, kainic acid (KA) has most frequently been employed to make localized excitotoxin lesions in the brain. The extent of the lesion can be controlled by varying the concentration of the amino acid solution, the volume of solution injected, and the rate of injection. Restricted excitotoxin lesions could be made equally well by microiontophoresis or with commercially available micropressure devices. Another method is the staining procedure. This procedure predominantly visualizes degenerating terminals and lysosomes. The rapid accumulation of lysosomes within degenerating somata presumably explains the ability of this procedure to visualize these structures as well. Few degenerating axons stain under the conditions described in the chapter. The procedure is very sensitive. One serious disadvantage is that only tissue that has been fixed in situ can currently be stained with this procedure. Therefore this method cannot be use ordinarily to verify lesions in animals from which tissue is taken for biochemical analysis.