Effects of S-2-(3-methylaminopropylamino)ethyl phosphorothioic acid (WR-3689), alone or combined with caffeine, on catecholamine content of mouse hypothalamus.

S-2-(3-Methylaminopropylamino)ethylphosphorothioic acid (WR-3689) is a radioprotective agent that is behaviorally toxic at radioprotective doses. It was recently reported that the combination of WR-3689 and caffeine ameliorated behavioral toxicity (determined by locomotor activity in mice) compared with WR-3689 alone. Since catecholamines can modulate locomotor activity, we determined norepinephrine (NE) and dopamine (DA) content (using high-performance liquid chromatography) in the hypothalamus of mice after treatment with WR-3689, caffeine, and the combination of the two drugs. CD2F1 male mice were injected intraperitoneally with saline (control), WR-3689 (100 and 200 mg/kg), caffeine (20 and 40 mg/kg), or the combination of WR-3689 (200 mg/kg) and caffeine (40 mg/kg). Control values for NE and DA ranged between 200 and 220 pg/mg and 69 and 94 pg/mg of hypothalamic tissue, respectively. WR-3689 had no effect on the content of NE and DA. In contrast, NE increased to (mean +/- SE) 324 +/- 27 pg/mg and 377 +/- 61 pg/mg (P < 0.05) 4 hr after injections of 20 and 40 mg/kg of caffeine, respectively. Similarly, DA increased to 142 +/- 13 pg/mg (P < 0.05) 4 hr after injection of 40 mg/kg of caffeine. The combination of WR-3689 and caffeine had no effect on NE and DA contents when compared with control values. These results suggest that WR-3689 can affect catecholamine metabolism in the mouse hypothalamus, but the mode of action is not clear.

Interleukin-1 inhibits serotonin release from the hypothalamus in vitro.

During a 60-min incubation period, the in vitro release of serotonin (5-HT) from the hypothalami of control male rats decreased by 12.3 +/- 3.1%. In contrast, the presence of 25 ng of interleukin-1 beta (IL-1 beta) in the incubation medium more than doubled this decrease to 29.3 +/- 3.3% (P < 0.001), and the presence of 50 ng of IL-1 beta more than quadrupled this decrease to 53.7 +/- 7.4% (P < 0.001). The decrease produced by the higher dose of IL-1 beta was significantly greater than that produced by the lower dose (P < 0.01), indicating a dose response. During the next two 60-min periods when the hypothalami of the control as well as treatment groups were incubated without IL-beta, 5-HT release continued to decrease and then became stabilized in the control group. In contrast, 5-HT release in the treatment groups rebounded before becoming stabilized at levels that were not significantly different from those in the control group. It is concluded that IL-1 beta inhibits the release of serotonin from the hypothalamus in vitro.

Cimetidine-associated adverse reaction.

Cimetidine, a histamine2-receptor antagonist, is used in the treatment and prophylaxis of peptic ulcer disease. Its use is relatively free of serious adverse reactions and only a few accounts of hypersensitivity exist. We report a case of intravenous cimetidine-associated adverse reaction characterized by junctional rhythm, bradycardia, and hypotension apparently not secondary to rapid intravenous cimetidine infusion. The adverse reaction was reproduced upon rechallenge. No previous accounts of this reaction appear clearly defined in the literature nor have such reactions been confirmed by rechallenge.

Interleukin-1 stimulates catecholamine release from the hypothalamus.

During a 60-min period, the in vitro release of norepinephrine (NE) from the hypothalami of male rats decreased by 28%. The presence of 50 or 100 ng of interleukin 1-beta (IL-1 beta) in the incubation medium prevented this decrease and raised the release by 17% or 45% respectively (P less than 0.05). The average release of dopamine (DA) decreased by 55% in the control group but 50 ng of IL-1 beta cut this decrease to 25%, and 100 ng of IL-1 beta not only completely prevented the decrease but raised the release by 44% (P less than 0.05). In a following 60-min period, when the hypothalami from the treatment groups were incubated without IL-1 beta, it resulted in sharp declines in the release of NE and DA, confirming that IL-1 beta was the stimulus for the increases in catecholamine release in the previous incubation period. It is concluded that IL-1 beta stimulates the release of catecholamines (and probably other neurotransmitters) in the brain which, in turn, mediate its central and neuroendocrine actions.

Plasma thyroxine and cortisol under basal conditions and during cold stress in the aging dog.

The effects of aging on plasma concentration of thyroxine (T4) and cortisol and on responses of these hormones to low ambient temperatures were determined in the dog. Female beagle dogs were divided into three age groups: old, adult, and puppies. The mean (+/- SD) ages were 11.4 +/- 0.2 years, 3.0 +/- 0.4 years, and 7.6 +/- 0.2 weeks, respectively. All dogs came from a genetically homogeneous colony and were free from any disease. The adult and old dogs were used during anestrus. Based on four daily blood samples, the mean (+/- SE) T4 level in the old dogs (2.8 +/- 0.1 microgram/dl) was significantly (P less than 0.001) lower than that in the adults (4.2 +/- 0.2 micrograms/dl) and puppies (4.4 +/- 0.2 micrograms/dl). By contrast, mean plasma cortisol levels in the old dogs (21.1 +/- 3.1 ng/ml) and adults (15.4 +/- 2.4 ng/ml) were significantly higher than those in the puppies (7.2 +/- 1.1 ng/ml). No significant changes in plasma T4 and cortisol occurred in any of the three age groups at 22 degrees C or during exposure to 10 or 4 degrees C. Exposure to -5 degrees C, however, produced significant increases in T4 (greater than 130% by 5 hr) and cortisol (greater than 280% by 1 hr) in adult dogs. This temperature produced only a modest increase in T4 (70% by 3.5 hr) and no change in cortisol in the old dogs. The puppies showed no change in T4 and cortisol during exposure to -5 degrees C. The results demonstrate that with advancing age, plasma T4 and cortisol concentrations change in opposite directions, thus supporting the hypothesis of a negative relationship between these two hormones. These results also show that the responses of these hormones to the stress of cold decline during aging and are not yet developed in the very young.

The effects of aging on the circadian rhythm of serum cortisol in the dog.

The purpose of this study was to determine if aging affects the circadian rhythm of serum cortisol. Female beagle dogs belonging to three age groups were used: adult (3.3 +/- 0.6 (SD) years), old (12.1 +/- 0.3 years), and puppies (8.4 +/- 0.2 weeks). Blood samples were collected by cephalic or jugular venipuncture at 3-h intervals during three 24-h periods and analyzed for total serum cortisol concentrations by radioimmunoassay. The circadian rhythm was present in the serum cortisol of adult animals, but no significant changes during a 24-h period could be detected in the old animals. No circadian rhythm in serum cortisol was present in the puppies. It is concluded that the circadian rhythm in plasma cortisol is disrupted in old animals and is not yet developed in puppies.