Rj. Walker et al., PHYSIOLOGICAL AND PHARMACOLOGICAL STUDIES ON ANNELID AND NEMATODE BODY-WALL MUSCLE, Comparative biochemistry and physiology. C. Comparative pharmacologyand toxicology, 106(1), 1993, pp. 49-58
1. This review covers the pharmacology and physiology of the body wall
muscle systems of nematodes and annelids. 2. Both acetylcholine and g
amma-aminobutyric acid (GABA) play important roles in the control of b
ody wall muscle in both phyla. In annelids and nematodes, acetylcholin
e is the excitatory neuromuscular transmitter while GABA is the inhibi
tory neuromuscular transmitter. In addition, 5-hydroxytryptamine (5-HT
) has a modulatory role at annelid body wall muscle but little if any
effect on nematode body wall muscle. 3. The acetylcholine receptor of
the body wall muscle can be classified as nicotinic-like in both phyla
though the annelid receptor has not been analysed in detail. In nemat
odes, vertebrate ganglionic nicotinic agonists were the most effective
of those so far examined while mecamylamine and benzoquinonium were t
he most effective antagonists. Both neuronal bungarotoxin and neosurug
atoxin were potent antagonists of acetylcholine excitation at the nema
tode receptor. 4. The GABA receptor of the body wall muscle exhibits s
imilarities with the vertebrate GABA-A receptor in both phyla. Picroto
xin is a very weak or inactive antagonist at leech and nematode GABA r
eceptors, while bicuculline methiodide blocks leech GABA receptors but
is inactive on nematode GABA receptors. Picrotoxin does block GABA re
sponses of earthworm body wall muscle. All these GABA responses are ch
loride mediated. 5. Neuroactive peptides of the RFamide family occur i
n both phyla and FMRFamide has been identified in leeches. RFamides pr
obably have an important role in heart regulation in leeches and in mo
dulation of their body wall muscles. RFamides also modulate nematode b
ody wall muscle activity with KNEFIRFamide raising muscle tone while S
DPNFLRFamide relaxes the muscle. It is likely that this family and oth
er neuroactive peptides play an important role in the physiology of bo
dy wall muscle throughout both phyla.