DIFFERENTIAL-EFFECTS OF A MOLTING HORMONE, 20-HYDROXYECDYSONE, ON THENEUROMUSCULAR-JUNCTIONS OF THE CLAW OPENER AND ABDOMINAL FLEXOR MUSCLES OF THE AMERICAN LOBSTER
Si. Cromarty et G. Kasssimon, DIFFERENTIAL-EFFECTS OF A MOLTING HORMONE, 20-HYDROXYECDYSONE, ON THENEUROMUSCULAR-JUNCTIONS OF THE CLAW OPENER AND ABDOMINAL FLEXOR MUSCLES OF THE AMERICAN LOBSTER, Comparative biochemistry and physiology. Part A, Molecular & integrative physiology, 120(2), 1998, pp. 289-300
Intracellular recordings at the neuromuscular junction of the dactyl o
pener muscle and the abdominal phasic flexor muscle of intermolt lobst
ers were made in the presence and absence of the steroid hormone, 20-h
ydroxyecdysone (20-HE). Evoked excitatory junctional potentials (EJPs)
were recorded from both muscles; spontaneous miniature excitatory jun
ctional potentials (MEJPs) were recorded from the claw. In the opener
muscle, 20-HE caused an increase in EJP amplitudes and MEJP frequency.
In the abdomen 20-HE caused EJP amplitudes to become significantly sm
aller than controls. These results are consistent with changes in the
relative activity of the two muscles over the molt cycle. In premolt l
obsters where the titers of 20-HE are highest, there is an increased t
endency towards aggressive behaviors (which include the meral spread)
and a corresponding reduction of escape swimming. The results also sup
port our earlier findings that one or more molt-related blood-borne fa
ctors can modulate peripheral synaptic transmission. (C) 1998 Elsevier
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