Effect of neurotoxic lesions in the mammillary bodies on the distribution of brain histamine

Abstract

Unilateral lesions with ibotenic acid in the vicinity of the mammillary bodies where the histamine (HA)-secreting neurons are located induced bilateral reductions in the levels of HA in the posterior hypothalamus (40-60%), anterior hypothalamus (45%), and frontal cortex (30%) as well as in the ipsilateral hippocampus (40%) 7 days after injection. Changes in the concentration of HA in the median eminence and adenohypophysis were not significant, but in the neurohypophysis the content of HA increased by 80%. These results seem to indicate that intrahypothalamic and cortical HA pathways are bilateral in origin while hippocampal HA pathways are predominantly ipsilateral.