Antinociceptive effect of R-(+)-hyoscyamine on the conjunctival reflex test in rabbits.
R-(+)-Hyoscyamine (1-10 microg/kg, s.c.) dose-dependently increased the local anesthetic effect of procaine (50 microg/ml) and lidocaine (50 microg/ml) in the conjunctival reflex test in the rabbit. This potentiating effect is completely prevented by the M1 antagonist dicyclomine (10 mg/kg, s.c.). The intensity of R-(+)-hyoscyamine antinociception was comparable to that induced by morphine (2 mg/kg, s.c.) and minaprine (15 mg/kg, s.c.), used as analgesic reference drugs. In the same experimental conditions, the S-(-)-enantiomer of atropine (0.1-10 microg/kg, s.c.), was completely ineffective. The present results confirm the ability of R-(+)-hyoscyamine to produce a paradoxical antinociceptive effect mediated by a cholinergic mechanism not only in rodents but also in the rabbit.
Ghelardini
C
C
Department of Pharmacology, University of Florence, Italy.
Galeotti
N
N
Fantetti
L
L
Gualtieri
F
F
Scapecchi
S
S
Bartolini
A
A
D000759:Adjuvants, Anesthesia / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000494:pharmacology; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology*; D001767:Blinking / Q000187:drug effects* / Q000502:physiology; D003228:Conjunctiva / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects*; D011343:Procaine / Q000494:pharmacology; D011817:Rabbits; D013237:Stereoisomerism
D000759:Adjuvants, Anesthesia; D000701:Analgesics, Opioid; D000779:Anesthetics, Local; D011343:Procaine; D009020:Morphine; D001285:Atropine; D008012:Lidocaine