Catecholamine Concentration and Turnover in Discrete Regions of the Brain of the Homozygous Brattleboro Rat Deficient in Vasopressin

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Abstract
The concentration of norepinephrine (NE), dopamine, and epinephrine and the turnover rate of these catecholamines [CA] were measured in 27 discrete regions of the brain of homozygous Brattleboro rats with diabetes insipidus (DI rats). These rats lack the capacity to synthesize vasopressin. The controls were homozygous nondiabetic rats. The NE concentration was elevated in the dorsal septal nucleus and the supraoptic nucleus of DI rats. The epinephrine concentration was lower in the paraventricular nucleus of DI rats than in that of control rats. CA turnover rate in the regions where differences were found was lower in the DI rats than in the controls. For NE this was the case in the periventricular nucleus, the medial forebrain bundle, the anterior hypothalamic nucleus, the arcuate nucleus, the parafascicular nucleus and the rostral part of the nucleus tractus solitarii; for dopamine this rate was lower in the caudate nucleus, the arcuate nucleus, the median eminence, the CA2 region of the hippocampus, and the A2 region; and for epinephrine the rate was lower in the periventricular nucleus, the paraventricular nucleus and the A2 region. The only exceptions were the dorsal septal nucleus and the supraoptic nucleus, where the turnover rate for NE was higher in the DI rats. In most cases the differences in CA turnover were in a direction opposite to that of the changes found in a previous study with Arg8-vasopressin administered intracerebroventricularly to normal Wistar rats. Brain vasopressin may modulate CA neurotransmission in defined brain regions. The absence of vasopressin from the brain of DI rats may cause altered neurotransmission in CA-containing neuronal systems and thus contribute to the impairment of neuroendocrine, autonomic and memory processes in these animals.