Repeated daily administration of an oral dose of 1000 mg of alpha-methyl-dopa (methyl dopa) to conscious dogs produced a conditioned adaptive hypertensive systolic and diastolic arterial pressure response along with the direct hypotensive pharmacological effect. The lower dose of 500 mg/day appeared to be devoid of direct or adaptive response effects, while the higher dose of 2000 mg/day only produced a blood pressure lowering response. The abrupt drug withdrawal unmasking the homeostatic state resulted in a marked systolic and diastolic pressor response which endured for about 10-days with peak effect reached at 17-days after termination of drug treatment. Comparable results were obtained whether the dogs were evaluated while in their normal horizontal body position or in a repositional upright condition.

Adaptation, Physiological↗

PubMedDate not supplied

An examination of the relationship between race, skin color and a series of autonomic nervous system measures.

In the total population of 75 subjects, the skin albedo correlated significantly with skin resistance, a relationship which was not maintained when the total population was separated into its component subgroups of whites, blacks and Indians. The Indians, "anthropologically Caucasians" but skin color more akin to the blacks, exhibited mean skin reflectance and skin resistance intermediate to that obtained in the black and white groups respectively. Other differences and significant correlations between the autonomic functions in the three groups indicated a higher level of sympathetic tone in the Indians, although this could be attributed to the older age of this group. It was suggested from the results that skin color rather than race has a greater influence on skin resistance.

Acoustic Stimulation↗

PubMedDate not supplied

Use of the pigmentometer, a new device for measuring skin albedo: relating skin color with a series of physiological measures.

Use of the Pigmentometer, a new device for measuring skin albedo: Relating skin color with a series of physiological measures. An apparatus has been described for the indirect measurement of skin albedo in human subjects. This device operates on the principle of the reflectance of light as influenced by the lightness or darkness of the skin. This new equipment was used to examine the relationship between lightness or darkness of the skin and the basal level and responsivity of some autonomic nervous system physiological variables in a series of 46 black and 47 white male and female subjects. It was observed that blacks had significantly lower (darker) skin albedo (PI), a significantly higher skin resistance (SR) and amplitude of the galvanic skin response (GSR), and an insignificant higher basal heart rate (HR). Pearson Product-Movement correlations between all measures from the total population showed significant relationships between PI and SR, SR and GSR and HR and HRR (heart rate response). The further separation of the total population into subgroups of blacks, whites, males, females, and black and white male and female goups, respectively, altered some of these differences and relationships previously observed. These results appeared to support the premise that race is more responsible for influencing the measured physiological responses, particularly SR, than is the lightness or darkness of the skin.

Age Factors↗

PubMedDate not supplied

Relationship between plasma diltiazem and cardiovascular responses in conscious dogs.

Conscious dogs were given diltiazem hydrochloride (DTZ) orally for 5 successive days at doses of 1, 3, and 10 mg/kg/day. During the 5th day, cardiovascular responses were monitored at various timed intervals after dosing. Arterial blood was sampled concomitantly for drug analysis. DTZ produced a dose-related decrease in blood pressure. The maximum reduction amounted to -30/-33 mm Hg in systolic/diastolic pressure, which occurred 90-150 min after the dose of 10 mg/kg. Heart rate and respiration were not significantly changed. There were dose-related alterations in the electrocardiogram tracing components, ranging from PR interval prolongation to junctional rhythms and ectopic beats. No overt physical responses were apparent. The mean DTZ peak plasma levels were approximately 708 ng/ml after 10 mg/kg, 224 ng/ml after 3 mg/kg, and 98 ng/ml after 1 mg/kg. The estimated t1/2 values for the 3- and 10-mg/kg/day dosings were 142 and 150 min, respectively. Correlations between the DTZ plasma level and the magnitude of the cardiovascular responses were highly significant in terms of blood pressure and PR interval changes. Low levels of DTZ were found 23 h after dosing. These levels were not associated with any meaningful cardiovascular activity.

Animals↗

PubMedDate not supplied

The results of alpha-adrenergic blockade on some behavioral and physiological effects of epinephrine.

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Anxiety↗