lnäuœd spawning
127
daily injections
of
10pg/kg.
The same authors
demonstrated that the effi—
ciency of
LHRH
administration
depends
on
the solvent used
(affecting the
kind of
release
of
LHRH)
since spermiation was not stimulated by 5 daily
injections of 10ug/kg of LHRHa dissolved in propylene
In
this
latter
caSe, plasma
GtH and
11—ketotestosterone were not modified compared to con—
trol.
On
the
other side, following the injections of 10Mg/kg of LHRHa dis—
solved
in
saline
an
increase
in
11—ketotestosterone levels was monitored as
long as
spermiation was stimulated i.e.
from 24 h after the first injection
until
24 hrs following the fifth…
3)
Release
of an
inhibition influencing spontaneous and GnRH
induced
GtH release.
PETER and
CRIM
1978 and PETER and PAULENCU 1980 have suggested the pre—
sence
of
a
gonadotropin release inhibitory factor (GRIF) in goldfish on the
basis of
brain
lesioning
experiments.
On the basis of in vivo studies on
goldfish CHANG
et
PETER
(1982,
1983a) demonstrated that dopamine has GtH
release
inhibitory
activity
by
acting directly on gonadotrophs to inhibit
spontaneous secretion of GtH and to block the action of GnRH. Removal of the
dopamine inhibition of GtH release by pimozide treatment, a dopamine antago—
nist, potentiates
the
ability of LHRHa to stimulate GtH release and ovula—
tion in
female
goldfish
at
12—1M°C
(CHANG et PETER 1983b) as well as 18 —
20°C
(SOKOLOWSKA
et
al"
198M).
Indeed
the
low
percentage of ovulation
(between 25%
—
50 %) obtained at 12 —14°C following LHRHa injection and at
18 —
20°C
following
LHRHa
treatment
(injection or pellet implantation) is
improved by
action
of
pimozide and can reach 80—90 %. The authors studied
the timing
of administration of pimozide and LHRHa allowing to optimize the
rate of
ovulation.
Best
results
were
obtained when pimozide is given prior
to the
injection
of
LHRHa or with
the
first of two injections of LHRHa or
following the
pellet
implantation° These observations indicates that prior
release from dopamine inhibition, greatly potentiates the ovulatory response
to LHRHa
as
well
as
GtH
release
since higher GtH levels were obtained in
this case.
A
transient increase in
17Π208 OH P and 17d OH P was observed in
such
treated fish before ovulation
(PETER
198ü)°
In
female
common
carp,
experiments
of
brain
lesioning
(PETER,
SOKOLOWSKA, BILLARD
and
CRIM unpublished) suggest that a GRIF is also pre—
sent.
Preliminary
promising
results
were
obtained with combined treatment
with pimozide
(10mg/kg)
and
LHRHa
(50 ug/kg) 6 hours later (BILLARD et al.
1983). This combination induced ovulation in some females (about 50 %) while
only oocyte
maturation
was
induced by LHRHa alone. Furthermore, promising
recent
results
on
the
success
of ovulation have been obtained in female
chi—
nese
carp
with pimozide + LHRHa and in female common carp with reserpine (a
catcholamine depletor) + LHRHa (LIN et al. 1986). On the other hand, in male
common
carp,
a
combination of LHRHa + pimozide had only a slight effect on
the stimulation
of
spermiation
when
compared
to
LHRHa
treatment alone
(BILLARD et al. 1983a).
4)
Action
of
factors
abating
the
negative
feed
back
effects
of
endogenous sex steroids on hypothalamo—hypophysial axis.
Antioestrogens
such
as
clomiphene citrate (clomid) or tamoxifen (ICI
l“3474) induce gonadotropin release in carp (BRETON et al. 1975) and goldfish
(BILLARD and
PETER
1977).
BRETON et al.
1975, comparing different dosages
(©,1mg —1mg — 10mg/kg) found that the dosage of 1mg/kg was the best to indu—
ce
high GtH levels similar to those present during ovulation in goldfish and
carp_ The
use
of
clomid
(10mg/kg) was successful in inducing ovulation in
€oldfish (PANDEY
and
HOAR
1972,
PANDEY
et
al
1973). In carp KUMAR and
CHANDRASEKHAR 1980
accelerated
spawning (4 months) by tri—weekly injections
Of Clomid (25 and 50 ug/animal) for a period of 3 months during the prepato—
PY period.
On mature animals
three
daily injections of 1mg/kg failed to in—
duce ovulation
(BIENIARZ
et
al, 1979)
while
two
successive injections of
higher dosage
(10mg/kg)
were
successful
in overcoming the blockade induced
127
daily injections
of
10pg/kg.
The same authors
demonstrated that the effi—
ciency of
LHRH
administration
depends
on
the solvent used
(affecting the
kind of
release
of
LHRH)
since spermiation was not stimulated by 5 daily
injections of 10ug/kg of LHRHa dissolved in propylene
In
this
latter
caSe, plasma
GtH and
11—ketotestosterone were not modified compared to con—
trol.
On
the
other side, following the injections of 10Mg/kg of LHRHa dis—
solved
in
saline
an
increase
in
11—ketotestosterone levels was monitored as
long as
spermiation was stimulated i.e.
from 24 h after the first injection
until
24 hrs following the fifth…
3)
Release
of an
inhibition influencing spontaneous and GnRH
induced
GtH release.
PETER and
CRIM
1978 and PETER and PAULENCU 1980 have suggested the pre—
sence
of
a
gonadotropin release inhibitory factor (GRIF) in goldfish on the
basis of
brain
lesioning
experiments.
On the basis of in vivo studies on
goldfish CHANG
et
PETER
(1982,
1983a) demonstrated that dopamine has GtH
release
inhibitory
activity
by
acting directly on gonadotrophs to inhibit
spontaneous secretion of GtH and to block the action of GnRH. Removal of the
dopamine inhibition of GtH release by pimozide treatment, a dopamine antago—
nist, potentiates
the
ability of LHRHa to stimulate GtH release and ovula—
tion in
female
goldfish
at
12—1M°C
(CHANG et PETER 1983b) as well as 18 —
20°C
(SOKOLOWSKA
et
al"
198M).
Indeed
the
low
percentage of ovulation
(between 25%
—
50 %) obtained at 12 —14°C following LHRHa injection and at
18 —
20°C
following
LHRHa
treatment
(injection or pellet implantation) is
improved by
action
of
pimozide and can reach 80—90 %. The authors studied
the timing
of administration of pimozide and LHRHa allowing to optimize the
rate of
ovulation.
Best
results
were
obtained when pimozide is given prior
to the
injection
of
LHRHa or with
the
first of two injections of LHRHa or
following the
pellet
implantation° These observations indicates that prior
release from dopamine inhibition, greatly potentiates the ovulatory response
to LHRHa
as
well
as
GtH
release
since higher GtH levels were obtained in
this case.
A
transient increase in
17Π208 OH P and 17d OH P was observed in
such
treated fish before ovulation
(PETER
198ü)°
In
female
common
carp,
experiments
of
brain
lesioning
(PETER,
SOKOLOWSKA, BILLARD
and
CRIM unpublished) suggest that a GRIF is also pre—
sent.
Preliminary
promising
results
were
obtained with combined treatment
with pimozide
(10mg/kg)
and
LHRHa
(50 ug/kg) 6 hours later (BILLARD et al.
1983). This combination induced ovulation in some females (about 50 %) while
only oocyte
maturation
was
induced by LHRHa alone. Furthermore, promising
recent
results
on
the
success
of ovulation have been obtained in female
chi—
nese
carp
with pimozide + LHRHa and in female common carp with reserpine (a
catcholamine depletor) + LHRHa (LIN et al. 1986). On the other hand, in male
common
carp,
a
combination of LHRHa + pimozide had only a slight effect on
the stimulation
of
spermiation
when
compared
to
LHRHa
treatment alone
(BILLARD et al. 1983a).
4)
Action
of
factors
abating
the
negative
feed
back
effects
of
endogenous sex steroids on hypothalamo—hypophysial axis.
Antioestrogens
such
as
clomiphene citrate (clomid) or tamoxifen (ICI
l“3474) induce gonadotropin release in carp (BRETON et al. 1975) and goldfish
(BILLARD and
PETER
1977).
BRETON et al.
1975, comparing different dosages
(©,1mg —1mg — 10mg/kg) found that the dosage of 1mg/kg was the best to indu—
ce
high GtH levels similar to those present during ovulation in goldfish and
carp_ The
use
of
clomid
(10mg/kg) was successful in inducing ovulation in
€oldfish (PANDEY
and
HOAR
1972,
PANDEY
et
al
1973). In carp KUMAR and
CHANDRASEKHAR 1980
accelerated
spawning (4 months) by tri—weekly injections
Of Clomid (25 and 50 ug/animal) for a period of 3 months during the prepato—
PY period.
On mature animals
three
daily injections of 1mg/kg failed to in—
duce ovulation
(BIENIARZ
et
al, 1979)
while
two
successive injections of
higher dosage
(10mg/kg)
were
successful
in overcoming the blockade induced