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Biomedical subjects

J P Spiers

Publications and source records attributed to J P Spiers.

5 recordsLinked to original sources
PubMed1991

Duration of action and effect on baroreflex function of the anti-arrhythmic alpha 1 antagonist UK-52,046.

The effects of acute and chronic oral administration of UK-52,046 (25 micrograms kg-1) on baroreflex function and its duration of action, were studied in conscious dogs. It was found that UK-52,046 had no effect on blood pressure and heart rate following acute and chronic administration. UK-52,046 shifted the phenylephrine dose response curve to the right, and the PE50 (measure of alpha 1-adrenoceptor antagonism) was increased (P less than 0.05) compared to placebo on day 1 (2, 4, 8 and 24 h) and day 8 (2, 4, 8 and 12 h). The antagonism was increased (P less than 0.05) on day 8 (0, 8 and 12 h) compared with day 1. Evaluation of the effects of UK-52,046 on baroreflex function using phenylephrine to increase blood pressure indicated no significant difference from placebo. It was concluded that at an antiarrhythmic dose, UK-52,046 has no effect on blood pressure, heart rate or baroreflex function. The pressor response curve was shifted to the right indicating a duration of action of at least 12 h on chronic oral administration.

Administration, Oral↗
PubMed1990

Acute and chronic effects of rilmenidine on baroreflex function in conscious dogs.

The effects of acute and chronic administration of rilmenidine on blood pressure, heart rate and baroreflex function were assessed in two groups of six conscious dogs. Baroreflex function was evaluated using increasing doses of glyceryl trinitrate and phenylephrine to decrease and increase blood pressure respectfully. Acute administration of rilmenidine (1 mg/kg p.o.) reduced (P less than 0.05) blood pressure and heart rate, and enhanced (P less than 0.05) baroreflex function to increases in blood pressure with phenylephrine, but not to decreases in blood pressure by glyceryl trinitrate. Following chronic administration of rilmenidine, blood pressure remained lowered while heart rate and baroreflex function returned to control values.

Adrenergic alpha-Agonists↗
PubMed1990

UK-52,046 (a novel alpha 1-adrenoceptor antagonist) and the role of alpha-adrenoceptor stimulation and blockade on atrioventricular conduction.

The effects of increasing intravenous (i.v.) doses of prazosin, phenylephrine, flecainide, and UK-52,046 on blood pressure (BP), heart rate (HR) and the specialized conduction system (AH and HV intervals) were investigated in anaesthetized dogs. Results indicated that UK-52,046 (1-8 micrograms/kg) had no effect on BP or HR, but reduced (p less than 0.05) BP at doses of 16 and 32 micrograms/kg; no change occurred in HR. During sinus rhythm (SR) the AH or HV intervals did not change as compared with placebo; on pacing (PA) UK-52,046 (4-16 micrograms/kg) decreased the AH interval. After prazosin BP decreased (p less than 0.05) after 20-40 micrograms/kg; HR increased after all doses (5-40 micrograms/kg). The HV interval was unaltered, but the AH interval decreased after 40 micrograms/kg during SR and PA. After phenylephrine (continuous infusion, 50 micrograms/ml/min) BP increased at 33 min and HR was decreased at 23 and 33 min. The AH interval lengthened during PA (p less than 0.05), but there was no effect on the HV interval. Administration of flecainide (0.5-2.0 mg/kg) had no effect on BP or HR but increased the HV interval during SR and PA (1 and 2 mg/kg, p less than 0.05). The results indicate that the alpha 1-adrenoceptor agonist phenylephrine and the alpha 1-adrenoceptor antagonist prazosin, on PA altered the AH (but not the HV) intervals in opposite directions in association with changes in HR and BP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗