The dopamine (DA) content of the canine renal cortex is greater than can be attributed to its presence in noradrenergic axons only. Most of the excess DA is in the outer part of the cortex. By fluorescence histochemistry numerous catecholamine-containing axons are seen to be associated with renal cortical arteries and arterioles. The fluorescence is abolished following treatment of animals with 6hydroxydopamine or with reserpine, but is restored to some axons if reserpine is followed by systemic administration of I-DOPA. This procedure does not restore fluorescence to atrial noradrenergic axons after reserpine-induced depletion. Pre-treatment of animals with guanethidine abolishes axonal fluorescence and depletes tissue NA and DA from atrium, but in renal cortex the tissue DA level is little affected and some fluorescent axons remain. These results are discussed in the light of previous functional evidence for dopaminergic autonomic axons in the canine kidney.

1. Physical dependence was induced in rats by administration of a slow release morphine emulsion (morphine SR), and assessed by scoring abstinence signs and temperature changes after i.p. administration of naloxone (5 mg/kg). Three groups of rats received doses of 75, 100 or 150 mg/kg of morphine SR. Dependence was evaluated in each of these groups after 24, 48 and 72 h. 2. The effect of these treatments at the different times on brain levels of serotonin, 5-hydroxyindoleacetic acid, noradrenaline and dopamine was determined. 3. A ceiling level of dependence was reached 24 h after 75 and 100 mg/kg and 48 h after 150 mg/kg of morphine SR. 4. These different treatments produced no significant effect on the brain levels of noradrenaline, dopamine or serotonin. The levels of 5-hydroxyindoleacetic acid were significantly raised in morphine-dependent rats and the changes correlated well with the changes in abstinence behaviour and temperature after naloxone. 5. The results suggest that a relationship exists between serotonin turnover and physical dependence on morphine.

Bio-Rex 70, a weak cation exchange resin, has been used to specifically isolate histamine from rat brain tissue. This method compares favourably to other extraction procedures with respect to selectivity, reproducibility and time taken to perform the procedure. However, because it combines the optimum of these properties, it appears more adaptable for routine laboratory use. Following isolation, histamine is quantified fluorometrically after condensation with o-phthaldialdehyde (OPT). The sensitivity of the procedure allows for the chromatographic isolation, using Bio-Rex 70, of 12.5 ng histamine to give fluorescence twice that of blank. In addition, the use of Bio-Rex 70 enables the selective separation of histamine from fluorescent contaminants such as spermidine. The stability and the reproducibility of the adsorption and elution characteristics of Bio-Rex 70 enables the determination of 30 brain samples in a working day. This method has been applied to determine whole brain and regional brain levels of histamine in control and L-histidine-treated rats. The whole brain level of histamine, which was 50 ng/g, was increased by L-histidine and the highest concentration of histamine was found in the hypothalamus. Since the reliability of existing histamine extraction procedures is questionable, under certain conditions, it is suggested that the use of Bio-Rex 70 is a valuable addition in evaluating the possible physiological role of brain histamine.

No abstract

No abstract