Further studies on the hypoxia produced by canatoxin in rats.
Canatoxin, a convulsant neurotoxin from the seeds of Canavalia ensiformis, induces lipoxygenase-dependent hypoxia in rats which is blocked by hexamethonium. The purpose of the present study was to examine the relationship between canatoxin-induced hypoxia and bronchoconstriction. Since several effects of the toxin are very similar to those described for morphine and opioid-like peptides, the effects of opioid antagonists were also investigated. Pretreatment of male, adult Wistar rats (200-250 g) with cyproheptadine (80 micrograms/kg, ip, N = 6) and isoproterenol (100 micrograms/kg, ip, N = 6) partially blocked (% variation of pO2: CNTX alone: -26.67 +/- 2.56, N = 6; with cyproheptadine: -16.15 +/- 2.97*, N = 6; with isoproterenol: -17.73 +/- 1.93*, N = 6; *P < 0.05 as compared to CNTX alone) the hypoxia but no effect was observed with diphenhydramine (2 mg/kg, ip, N = 6) or atropine (2 mg/kg, ip, N = 6). The hypoxemic effect of canatoxin (100 micrograms/kg, i.v., 20 min, N = 6) was also almost completely blocked with either naloxone (1 mg/kg, sc, N = 6) or naltrexone (5 mg/kg, sc, N = 6). The results presented here provide evidence suggesting that both opioid peptides and bronchoconstriction seem to play a role in the hypoxia caused by canatoxin.
Ribeiro-DaSilva
G
G
Departamento de Farmacologia, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, SP, Brasil.
Prado
J F
JF
Collares
C B
CB
Siste-Campos
M
M
D000818:Animals; D016084:Bronchoconstriction / Q000187:drug effects; D001993:Bronchodilator Agents / Q000494:pharmacology; D004347:Drug Interactions; D000860:Hypoxia / Q000097:blood / Q000139:chemically induced*; D037102:Lectins / Q000494:pharmacology*; D008297:Male; D009292:Narcotic Antagonists / Q000494:pharmacology; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D010940:Plant Proteins; D051381:Rats; D017208:Rats, Wistar; D014118:Toxins, Biological / Q000494:pharmacology*
D001993:Bronchodilator Agents; D037102:Lectins; D009292:Narcotic Antagonists; D010940:Plant Proteins; D014118:Toxins, Biological; C032815:canatoxin; D010100:Oxygen