CHARACTERIZATION OF 2 MYOTROPIC NEUROPEPTIDES IN THE FMRFAMIDE FAMILYFROM SEGMENTAL GANGLIA OF THE MOTH MANDUCA-SEXTA - CANDIDATE NEUROHORMONES AND NEUROMODULATORS
Tg. Kingan et al., CHARACTERIZATION OF 2 MYOTROPIC NEUROPEPTIDES IN THE FMRFAMIDE FAMILYFROM SEGMENTAL GANGLIA OF THE MOTH MANDUCA-SEXTA - CANDIDATE NEUROHORMONES AND NEUROMODULATORS, Journal of Experimental Biology, 199(5), 1996, pp. 1095-1104
We have characterized two new members of the FMRFamide family of neuro
peptides from the segmental ganglia of the tobacco hornworm Manduca se
xta. Levels of peptides in ganglia used for purification were enhanced
by manipulating their exposure to the steroid molting hormones. Expla
nts of ganglia were cultured in the low-level ecdysteroid environment
of diapausing pupae shown previously to evoke accumulation of FMRFamid
e-like immunoreactivity (FLI). Sufficient material for sequencing was
obtained from 180 explanted ganglia. Extracts of ganglia were fraction
ated using two reverse-phase liquid chromatography procedures, and the
immunoreactive fractions were subjected to sequence analysis using el
ectrospray mass spectrometry. The sequences of the two peptides were d
etermined to be GNSFLRFamide and DPSFLRFamide. These peptides have bee
n named MasFLRFamide II and MasFLRFamide III, respectively; the previo
usly characterized M. sexta FLRFamide (pEDVVHSFLRFamide) has been rena
med MasFLRFamide I. The three peptides show distinctive tissue and dev
elopmental distributions as determined from fractionated extracts of l
arval and adult central nervous system structures and neurohemal organ
s. In the retrocerebral corpora cardiaca/corpora allata, MasFLRFamide
I was the predominant form, while in the segmental ganglia MasFLRFamid
es II and III predominated. Higher levels of MasFLRFamide I and II wer
e found in the adult, whereas there was little apparent change in the
level of MasFLRFamide III upon metamorphosis. Determinations of peptid
e levels in fractionated hemolymph of newly emerged moths revealed tha
t levels of MasFLRFamide I and III could exceed 10 nmol l(-1). The act
ions of the three peptides were tested on the moth ileum, MasFLRFamide
s II and III were found to be stimulatory. At 1 nmol l(-1), these pept
ides induced robust increases in the rate of rhythmic longitudinal and
peristaltic waves of contractions. In contrast, MasFLRFamide I was in
effective even at 20 nmol l(-1). Thus, while all three peptides have t
he characteristics of neurohormones in M. sexta, the physiological fin
dings show that the heptapeptide FLRFamides have properties distinct f
rom those of the decapeptide.