Lateral hypothalamic self-stimulation pathways in Rattus norvegicus

Self-stimulation in lateral hypothalamus involves the activation of several ascending and descending fiber systems. In an effort to define these fiber systems, self-stimulation loci were studied with a single low current level and bipolar nichrome electrodes made with wire 78.7 μ dia. Prograde degeneration revealed by the Fink-Heimer technique and retrograde chromatolytic changes were described following lesions at self-stimulation sites. Neuronal activity following electrical stimulation of self-stimulation sites was also used to define the functional influence of these fiber systems. The relationship with the extrapyramidal system was emphasized, with convergent evidence suggesting an intimate relation between lateral hypothalamic neurons and those of substantia nigra, pars compacta.