The origin of neuropeptide Y(NPY)-like immunoreactive(IR)fibers in the lateral and basolateral amygdaloid nuclei was examined by using indirect immunofluorescence and retrograde tracing method in the rat.1njection of a retrograde tracer.fluorogold(FG),into the lateral and basolateral amygdaloid nuclei,labeled many neurons in the ipsilateral anterior amygdaloid area,and simultaneous treatment with antiserum against NPY stained some of these neurons.Destruction of the anterior amygdaloid area caused an ipsilateral decrease of NPY-IR fibers in the lateral and basolateral amygdaloid nuclei.These findings indicate that NPY-IR neurons in the anterior amygdaloid area project ipsilaterally to the lateral and basolateral amygdaloid nuclei.In addition,the present study also shows that NPY-IR neurons located in the lateral and basolateral amygdaloid nuclei are intrinsic to the amygdaloid complex,since after destruction of the anterior amygdaloid area,some of NPY-IR fibers still can be found in lateral and baso lateral nuclei,and transection of the two major amygdalofugal system,stria terminalis and ventral amygdalofugal pathway,failed to cause the accumulation of NPY-like immunoreactivity in the axons proximal to the section.