Effects of levodropropizine on vagal afferent C-fibres in the cat.
1. Levodropropizine (LVDP) is an effective antitussive drug. Its effects on single-unit discharge of vagal afferent C-fibres were tested in anaesthetized cats to assess whether an inhibition of vagal C-fibres is involved in its antitussive properties. Vagal C-fibres, identified by their response to phenylbiguanide (PBG), were recorded via suction electrodes from the distal part of the cut vagus. Based on their response to lung inflation, C-fibres were classified as pulmonary (19 fibres) or non-pulmonary (6 fibres). 2. PBG increased the discharge rate of both C-fibre types and activated a respiratory reflex causing apnoea. This reflex was abolished when the second vagus nerve was cut as well, while PBG-mediated stimulation of the C-fibres was not affected by vagotomy. 3. LVDP was administered intravenously and the C-fibre response to PBG was compared with that before administration of the drug. LVDP reduced both the duration of apnoea and the response of the C-fibre to PBG. 4. Comparison of the C-fibre responses to PBG and to a mixture of PBG and LVDP revealed that the period of apnoea was shortened and the discharge rate of the C-fibre reduced when LVDP was present. 5. The LVDP-induced inhibition of the C-fibre response to PBG was on average 50% in pulmonary and 25% in non-pulmonary fibres. 6. These results suggest that LVDP significantly reduces the response of vagal C-fibres to chemical stimuli. It is, thus, likely that the antitussive effect of LVDP is mediated through its inhibitory action on C-fibres.
Shams
H
H
Institut für Physiologie, Ruhr-Universität Bochum, Germany.
Daffonchio
L
L
Scheid
P
P
D000818:Animals; D000996:Antitussive Agents / Q000494:pharmacology*; D001645:Biguanides / Q000494:pharmacology; D002415:Cats; D005260:Female; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects*; D011409:Propylene Glycols / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects; D014630:Vagus Nerve / Q000187:drug effects*
D000996:Antitussive Agents; D001645:Biguanides; D011409:Propylene Glycols; C035916:dipropizine; C008846:phenyl biguanide