Galanin-like immunoreactivity within amygdaloid and hypothalamic neurons that project to the midbrain central grey in...

The possibility that galanin-immunoreactive cells within the central nucleus of the amygdala (Ce) and the lateral part of the bed nucleus of the stria terminalis (BSTL) project to the midbrain central grey in the rat was investigated using the combined immunofluorescence-retrograde tracing technique. Injections of Fluoro-Gold tracer were made into the ventrolateral midbrain central grey and the brain tissue was processed for galanin-like immunoreactivity using the avidin-biotin Texas red immunofluorescence technique. Cells containing both galanin-like immunoreactivity and fluorescent retrograde tracer were identified within the medial Ce and in the ventral part of the BSTL. Retrogradely labeled galanin-like immunoreactive cells were also observed within the medial preoptic area and to a lesser extent within the dorsomedial and paraventricular hypothalamic nuclei. The results of this study demonstrate the presence of long descending pathways containing galanin-like immunoreactivity that originate from discrete regions of the amygdala and hypothalamus and terminate within the midbrain central grey.