Abstract |
Intravenous injection of opiates in rats is known to produce a rapid fall in heart rate, blood pressure, and respiratory frequency. Etorphine, a potent opiate agonist which reaches central and peripheral receptors, administered at 1.1 nmol/kg i.v., evoked these characteristic effects in the urethane-anaesthetized rat. Three opiate antagonists, with somewhat different properties, have been used to assess the site of action of etorphine-induced bradycardia, hypotension, and inhibition of respiration. The antagonists used were naloxone hydrochloride, N-methylnaloxone bromide, and SMS 201-995. Low doses of naloxone blocked the cardiovascular and respiratory effects of etorphine. N-Methylnaloxone blocked the bradycardia, hypotension and the initial phase of apnea produced by etorphine but not the subsequent slowing of respiration. SMS 201-995 blocked the bradycardia and partially antagonized the hypotension and inhibition of respiratory rate produced by etorphine. These results indicate that N-methylnaloxone and SMS 201-995 can block the peripheral receptors which mediate opiate-induced bradycardia. Naloxone blocks both the central and peripheral actions of etorphine and so more completely antagonizes the cardiovascular and respiratory effects of etorphine.
|
Authors | M R Dashwood, J G Kiang, E T Wei |
Journal | Archives internationales de pharmacodynamie et de therapie
(Arch Int Pharmacodyn Ther)
Vol. 266
Issue 1
Pg. 77-82
(Nov 1983)
ISSN: 0003-9780 [Print] Belgium |
PMID | 6198981
(Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)
|
Chemical References |
- Morphinans
- Naloxone
- Etorphine
- Somatostatin
- Oxymorphone
- Hydromorphone
- Octreotide
|
Topics |
- Animals
- Blood Pressure
(drug effects)
- Etorphine
(antagonists & inhibitors)
- Heart Rate
(drug effects)
- Hydromorphone
(analogs & derivatives)
- Male
- Morphinans
(antagonists & inhibitors)
- Naloxone
(pharmacology)
- Octreotide
- Oxymorphone
(pharmacology)
- Rats
- Rats, Inbred Strains
- Reflex
(drug effects)
- Respiration
(drug effects)
- Somatostatin
(analogs & derivatives, pharmacology)
- Vagus Nerve
(physiology)
|