Total and partial hypothalamic deafferentations for topographical identification of catecholaminergic innervations of...

After total deafferentation of the medial hypothalamus in the rat, noradrenaline concentration in the nucleus arcuatus and the eminentia mediana diminished to one-third. The same decrease of noradrenaline concentration resulted also from partial (anterolateral) deafferentation. Rostral and caudal cuts from the medial hypothalamus did not induce any change in the noradrenaline concentration of the two above-mentioned areas. This indicates that noradrenaline containing axons enter the medial basal hypothalamus laterally from the medial forebrain bundle. Total or partial deafferentation of themedial hypothalamus did not affect noradrenaline or dopamine concentrations in the nucleus preopticus medialis, the nucleus interstitialis striae terminalis, the nucleus hypothalamicus anterior and nucleus supraopticus. The catecholaminergic fibres supplying these regions do not pass the medial hypothalamus, but probably ascend laterally from it, in the medial forebrain bundle. The noradrenaline innervation of the nucleus dorsomedialis takes its origin in the ventral noradrenaline bundle and the fibres from the medial forebrain bundle ascend into the nucleus from the lateral side. After total or lateral deafferentation of the medial hypothalamus, that ransects the fibres running to the nucleus laterally, noradrenaline concentration decreases, apart from the nucleus located within or outside the deafferented island. In this case anterior or posterior deafferentation of the hypothalamus is ineffective. Total deafferentation did not change dopamine concentration in the nuclei of the medial basal hypothalamus, thereby furnishing evidence for its intrahypothalamic origin from the A12 cell group. However, after total deafferentation, some slight decrease of dopamine concentration could be observed in the median eminence. This suggests that the dopamine concentration in the median eminence does not originate exclusively from thenucleus arcuatus but to some extent originates from extrahypothalamic sites. After posterior deafferentation, which destroys the fibres of the incertohypothalamic dopamine system, dopamine concentration in the nucleus dorsomedialis decreases. After total deafferentation of the medial hypothalamus, which isolates the nucleus from the ventral nuclei (and so also from the A12 cell group) of the medial hypothalamus, the dopamine concentration in the nucleus dorsomedialis did not change.