ISSN:
1432-1912
Keywords:
Capsaicin
;
Cholinergic mechanism
;
Periarterial mesenteric nerves
;
Sensory fibres
;
Ileum innervation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The site and mode of action of capsaicin were analysed on the guinea-pig isolated ileum. 1. Capsaicin produced longitudinal contraction (EC50 4.2×10−8 g/ml) followed by a specific, rapid and irreversible tachyphylaxis (IC50 2.8×10−7 g/ml). 2. Capsaicin was ineffective in the presence of tetrodotoxin (2×10−7 g/ml) or on ilea kept for 24–48 h at 4°C, without an oxygen supply. 3. On ileal segments, the perivascular mesenteric nerves of which were transsected 5–8 days before the experiment, practically no response to capsaicin was obtained. Chronic abdominal bilateral vagotomy was without any effect. 4. Hyoscine (1×10−8–1×10−6 g/ml) or morphine (2×10−6 g/ml) strongly inhibited contractions produced by capsaicin. Neither mecamylamine (1×10−5 g/ml), nor nicotine (5×10−5 g/ml) and dimethylphenylpiperazinium (5×10−6 g/ml) caused any change, while an increased response to capsaicin was obtained in the presence of hexamethonium (1×10−4 g/ml). 5. Unaltered contractions were produced by capsaicin on ileal segments made tachyphylactic to 5-HT, bradykinin or substance P. Histamine antagonists at H1 and H2 receptors (chloropyramine, burimamide), the prostaglandin synthesis inhibitor indomethacin, pretreatment with the adrenergic neuron blocking agent guanethidine, as well as in vivo reserpine pretreatment were also ineffective in this respect. 6. It is concluded that in the guinea-pig ileum capsaicin causes predominantly cholinergic contraction by stimulating terminals of extrinsic, non-parasympathetic nerves.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00497008
Permalink
