Effect of β‐adrenoceptive blocking agents on the response to bronchoconstrictor drugs in the guinea‐pig air overflow preparation

Abstract

Summary Propranolol augmented the bronchoconstrictor response to methacholine or histamine, recorded by air overflow in the anaesthetized, vagotomized guinea‐pig. After adrenalectomy, propranolol was still active, though less so than before. In the pithed guinea‐pig, there was no augmentation of the effect of bronchoconstrictors on air overflow. The action of propranolol could thus be due to the β‐adrenoceptor blockade of compensatory sympathetic bronchodilator activity, as concluded by McCulloch, Proctor & Rand (1967). Electrical stimulation of the thoracic region of the spinal cord of the pithed guinea‐pig reduced the effect of bronchoconstrictors on air overflow. This reduction could be blocked by propranolol; practolol was much less effective.

The SELECTIVITY OF Β‐ADRENOCEPTOR ANTAGONISTS ON CARDIOVASCULAR AND BRONCHODILATOR RESPONSES TO ISOPRENALINE IN THE ANAESTHETIZED DOG

“…Thus, whereas there are reports that practolol has no specificity in this respect in guinea-pigs (Burden & Parkes, 1971) and dogs (Boissier et al, 1971) it has also been claimed that practolol has a relatively greater effect on cardiac responses in both guinea-pigs (Baird & Linnell, 1972) and cats (Parkes, 1973). The reasons for these differences are not known; the degree of selectivity could vary somewhat depending on the species and the method of assessment used (Basil et al, 1973).…”

The detection of differential β‐adrenoceptor blockade in the cat

“…The air overflow was detected by a pneumotachograph (Fleisch tube) connected to a differential micromanometer as described in a modification of that method (Burden et at., 1971). The signal from the micronomanometer was processed by the device described in the Appendix to give an output to a pen recorder representing the volume of overflow per respiratory cycle.…”

“…A device for cycle-by-cycle spirometry D. G. GARDINER The Appendix to a recent paper (Burden et al, 1971) described an arrangement for recording changes in resistance to inflation of the lungs in vivo, by the measurement of air overflow with a pneumotachograph and differential manometer, which depends on continuous integration of the manometer signal. The present device displays the integrated signal over each cycle successively.…”

“…The device is the subject of a current patent application (Gardiner, 1971) and was demonstrated to the British Pharmacological Society in January 1972 (Gardiner & Parkes, 1972). Description Figure 5 shows the stages in the cycle of air inflation of the lungs, by means of a pump, to constant pressure using a water-valve in parallel (Burden et al, 1971).…”

“…In a recent study of /8-adrenoceptor blockade of the effects upon heart rate and airway resistance of thoracic cord stimulation in the guinea-pig (Burden, Parkes & Gardiner, 1971), it was found that propranolol appeared more active in blocking effects upon heart rate than upon airway resistance, while practolol was similarly effective against both effects. To test the possibility that this unexpected result might have been a characteristic of the species used, a similar comparison has been made in the cat.…”