Pulmonary vagal afferent stimulants in the conscious rat: Opioids and phenyldiguanide

• Published in: Pharmacology, biochemistry and behavior Vol. 17; no. 1; pp. 19 - 23
• Main Authors: Willette, R.N., Gatti, P., Gertner, S.B., Sapru, H.N.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.1982
• Subjects: Animals; Biguanides - pharmacology; Cardiovascular reflex; Enkephalin; Hemodynamics - drug effects; Lung - innervation; Male; Morphine; Motor activity; Motor Activity - drug effects; Narcotics - pharmacology; Neurons, Afferent - drug effects; Postural Balance - drug effects; Pulmonary J-receptors; Pulmonary opiate receptors; Rats; Rats, Inbred Strains; Stimulation, Chemical; Vagal afferents; Vagus Nerve - drug effects; Cardiovascular reflex; Motor activity; Enkephalin; Morphine; Vagal afferents; Pulmonary opiate receptors; Pulmonary J-receptors
• ISSN: 0091-3057; 1873-5177
• DOI: 10.1016/0091-3057(82)90256-8

Phenyldiguanide (PDG, 40 μg/kg), D-ala 2-met 5-enkephalinamide (D-AME, 250 μg/kg) and morphine sulfate (MS, 2 mg/kg) injected into the right atrium (RA) of conscious freely moving rats produced a profound bradycardia and hypotension 1–2 sec subsequent to administration. Concomitant with the cardiovascular effects apnea occurred and lasted approximately 5 sec. Atropine methyl nitrate (2 mg/kg, RA) significantly attenuated the bradycardia and hypotension produced by all three agents. Naloxone blocked only the opioid responses. Coordinated motor activity was impaired following the administration of PDG (40 μg/kg, RA). Fifty percent of the animals receiving PDG failed to remain on a rotor rod for a 2 min period. Only 8 percent of the saline treated group fell off during this period. It was concluded that the cardiovascular, respiratory, and motor effects caused by PDG, in the conscious freely moving rat, were the result of stimulation of pulmonary vagal afferents (J-receptors). The cardiovascular effects of opioids are also believed to arise from the stimulation of J-receptors. However, unlike PDG, these effects are mediated by pulmonary opiate receptors.