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The porphyrin precursor, delta-aminolaevulinic acid (ALA) at concentrations of 0.23-7.6 mM caused dose-dependent inhibition of spontaneous contractions in isolated preparations of rabbit small intestine, suspended in Ringer-Locke solution. Contractions which returned after inhibition from 3.8 and 7.6mM ALA showed increased amplitude and from 7.6 mM ALA a reduction in rate. Pretreatment with prazosin (10(-7) M) significantly reduced the duration of inhibition exerted by 3.8 and 7.6 mM ALA and also the amplitude of contractions returning after this inhibition. Pretreatment with yohimbine (10(-6) M) and propranolol (7 X 10(-6) M) had no significant effects. Blocking of the release of noradrenaline in preparations by incubation with 6-hydroxydopamine (10(-3) M) or guanethidine (1.5 X 10(-5) M) did not prevent the inhibitory effects of ALA. The alpha 1 agonist, cirazoline (10(-5) M), inhibited contractile activity. This effect was blocked by prazosin (10(-7) M). The alpha 2 agonist, guanoxabenz (10(-5) M) had no detectable effect, in the presence of prazosin, to block any residual alpha 1 actions. It is concluded that alpha 1 receptors mediate inhibitory effects in this preparation and that ALA appears to have direct effects upon these receptors.
M G Cutler, and
M McLaughlin, and
E McNeil, and
M R Moore
June 1980,
European journal of pharmacology,
M G Cutler, and
M McLaughlin, and
E McNeil, and
M R Moore
January 1991,
Toxicology in vitro : an international journal published in association with BIBRA,
M G Cutler, and
M McLaughlin, and
E McNeil, and
M R Moore
March 1970,
Nihon Heikatsukin Gakkai zasshi,
M G Cutler, and
M McLaughlin, and
E McNeil, and
M R Moore
January 1988,
Fiziologicheskii zhurnal SSSR imeni I. M. Sechenova,
M G Cutler, and
M McLaughlin, and
E McNeil, and
M R Moore
April 2011,
Acta pharmacologica Sinica,
M G Cutler, and
M McLaughlin, and
E McNeil, and
M R Moore
October 1995,
British journal of cancer,
M G Cutler, and
M McLaughlin, and
E McNeil, and
M R Moore
November 1978,
British journal of haematology,
M G Cutler, and
M McLaughlin, and
E McNeil, and
M R Moore
May 1969,
The Journal of physiology,
M G Cutler, and
M McLaughlin, and
E McNeil, and
M R Moore
March 1996,
Journal of photochemistry and photobiology. B, Biology,
M G Cutler, and
M McLaughlin, and
E McNeil, and
M R Moore
January 1983,
Acta physiologica Polonica,
