Ascaris suum contains a large number of FMRFamide-related
peptides (FaRPs) of which
KHEYLRFamide (AF2) and KSAYMRFamide (AF8, also called PF3) have been extensively
studied and are known to
exert actions on somatic muscle strips of the worm. In the present study,
the effects of AF1, AF2
and AF8 on the activity
of the vagina vera of female A. suum have been examined in
vitro. The vagina vera
is a muscular tube connecting the uterus
and vagina uteri to the gonopore and is probably involved in regulating
egg output. The tissue
rhythmic contractions in vitro, which were modulated by each of
the FaRPs tested.
The effects of each of the peptides
were qualitatively and quantitatively different, and in each case were
(1 μM) caused a biphasic response
in the form of a transient lengthening of the preparation, followed by
contractions were initially inhibited
but resumed 5 min post-addition of the peptide. Lower concentrations
([les ]0·1 μM) induced a less marked effect, with
rhythmic contractions returning 5 min post-addition. AF2 and AF8 reduced
at concentrations [ges ]0·1 μM. Both peptides also caused
the tissue to shorten,
although the effects of AF8 on baseline tension were inconsistent.
The apparent potencies of AF1 and AF8 on contraction frequency of the vagina
vera were 10-fold greater than AF2 and,
unlike their actions on A. suum somatic body wall muscles, the
AF1 and AF2 were qualitatively different.
Indeed, the effects of each of these FaRPs on the vagina vera were markedly
from those observed on the somatic muscle.