Cytometric investigations in histochemically identified neurons — Changes of fluorescence intensities and nuclear diameters in dopamine neurons of the arcuate nucleus in the cycling rat

Summary The relative formaldehyde-induced fluorescence intensities and the diameter of cell nuclei of fluorescent perikarya of the arcuate nucleus were recorded in serial cross-sectioned hypothalamic arcuate nuclei of regularly cycling rats (5 estrous and 4 proestrous animals). Stress-induced changes of cytometric parameters were avoided by preadaptation of animals to handling procedures. Dopamine neurons in a 75 m thick periventricular layer of the arcuate nucleus exhibited significantly smaller nerve cell nuclei and significantly reduced relative fluorescence intensities in proestrous rats. Both of these cytometric parameters indicate a decrease in the activity of periventricular dopamine neurons of the arcuate nucleus. The reported findings might support the hypothesis that dopamine inhibits the release of LH-RH.In partial fulfillment of requirements for an academic degree (Dr. med.)Supported by a grant from the Deutsche Forschungsgemeinschaft (-Ha 726/5-) and the Stiftung Volkswagenwerk (I/35 582) to H.G.H.