Effect of postural changes on aldosterone to plasma renin ratio in patients with suspected secondary hypertension.

AIMS: To study the influence of postural changes on aldosterone to renin ratio (ARR) in patients with suspected secondary hypertension and to evaluate the sensitivity and specificity of the recommended seated ARR compared to supine and upright ARR for primary aldosteronism screening. METHODS: Fifty-three hypertensive patients were prospectively hospitalized for secondary hypertension exploration (age: 51 ± 12, 66% males). After withdrawal of drugs interfering with renin angiotensin system, plasma aldosterone and direct renin concentration were measured in the morning, at bed after an overnight supine position, then out of bed after 1 hour of upright position and finally 2 hours later after 15 minutes of seating. Minimal renin value was set at 5 µUI/mL. RESULTS: Referring to ARR cut-off of 23 pg/µUI, the sensitivity of seated ARR was 57.1% and specificity was 92.3%. The negative and positive predictive values were 95.1% and 45.2% respectively. Compared to these results, a cut-off of 19 improved sensitivity to 85.7% with a specificity of 89.7%. Negative and positive predictive values were 98.3% and 41.1% respectively. Seated ARR mean value was lower than supine and upright ARR mean values, due to an overall increase in renin at seating compared to the supine position by factor 1.9 while aldosterone just slightly increased by factor 1.2. Seated ARR correlated to supine and upright ARR: correlation coefficients (r) 0.90 and 0.93 respectively (P<0.001). CONCLUSIONS: Current recommended measurement of ARR in the seating position is fairly correlated to supine and upright ARR. A suggested cut-off value of 19 instead of 23 pg/µUI increased the discriminating power of this test.

Effects of abstinence on self-selection of ethanol induced by uncertainty in monkeys.

Of nine monkeys, three subjected to an experimental condition of uncertainty drank more ethanol than did three subjected to a learning task but no uncertainty and three subjected to no testing. The differential rates of consumption reappeared following 10 weeks of abstinence.

Effect of uncertainty on emotionality and ethanol self-selection in monkeys with cortical ablations.

Alcohol selection and emotionality were examined in rhesus monkeys with frontal cortical ablations which had been subjected to stress via an "uncertainty" paradigm. Uncertainty produced a higher selection of alcohol as compared to nonstress situations. Controls and dorsolateral subjects when exposed to uncertainty selected more of an alcohol solution than either orbital stressed or control-nonstressed animals. Emotionality changes during alcohol-loading and control conditions were measured by recording the number of aggressive or aversive behaviors. Dorsolateral ablations increased the number of aggressive responses while decreasing the number of retreats in the alcohol-loading condition. In the other groups, alcohol loading did not affect the incidence of aggressive or aversive behaviors although they exhibited more retreats than advances across both conditions. Control-nonstressed subjects yielded the lowest number of total aggressive behaviors and the highest number of total retreats.

Maintenance of responding by fixed-interval schedule of electric shock presentation in squirrel monkeys.

After stabilization of response rates engendered by a free-operant avoidance contingency, the lever-pressing of two squirrel monkeys was maintained for several months by a fixed-interval schedule of electric shock presentation. Initially, response-contingent shocks produced substantial increases in response rates. Continued exposure to the schedule resulted in a reduced overall rate accompanied by a change in the temporal patterning of responses. There was a pause in responding after most shock deliveries; the rate of responding then increased during the interval to reach a terminal value preceding shock presentation. Omission of shocks for part of the daily session led to higher rates of responding; the reintroduction of response-contingent shocks produced a lower overall rate and reinstated the temporal patterning of responding characteristic of the fixed-interval schedule.