Effects of annetocin, an oxytocin‐related peptide isolated from the earthworm Eisenia foetida, and some putative neurotransmitters on gut motility of the earthworm

Abstract

Annetocin, an oxytocin-related peptide recently isolated from the lumbricid earthworm Eisenia foetida, and putative transmitter substances were examined for their effects on rhythmic, spontaneous contractions of isolated gut preparations of the earthworm. Significant, dose-dependent effects of the following substances were observed: acetylcholine (ACh), gamma-aminobutyric acid (GABA), and dopamine were excitatory, while serotonin (5-HT) and octopamine were inhibitory. Annetocin, oxytocin, and vasotocin stimulated spontaneous contraction of the earthworm gut, annetocin being approximately 10-fold more potent than oxytocin or vasotocin. However, arginine-vasopressin (Arg-vasopressin), lysine-vasopressin (Lys-vasopressin), tocinoic acid (N-terminal hexapeptide fragment of oxytocin), and MSH release-inhibiting factor (MIF; C-terminal tripeptide fragment of oxytocin) did not show any effect on the earthworm gut motility. On the other hand, oxytocin, vasotocin, Arg-vasopressin, Lys-vasopressin, and tocinoic acid caused spontaneous contractions of isolated rat uterine preparations, where the potency was in this order, while annetocin and MIF exerted no oxytocic activity on the uterus. Dose-response relationship of the effects of annetocin and its related peptides on the annelid and mammalian systems shows that amino acid residue at the third position of these peptides is important for exertion of excitatory action on the smooth muscle systems. The results in the present study suggest that receptors for annetocin and for GABA on the earthworm gut, unlike those for ACh, desensitize during continuous exposure to these substances.

Cloning, expression and pharmacological characterization of a vasopressin-related receptor in an annelid, the leech Theromyzon tessulatum

“…Our results are in good agreement with the fact that Lys-conopressin and annetocin, when injected in leeches and earthworms, induce rapid egglaying-like behaviour accompanied by much mucus secretion. Furthermore, leeches in the non-breeding season responded to peptides less conspicuously than those in the breeding season, suggesting that the involvement of peptides in the control of reproductive events is periodical (Ukena et al 1995. These findings also correlate well with the pond snail LSCPR functions that induce muscle contractions of the vas deferens, thus stimulating the transport of both eggs and semen during copulation and inhibiting the central neuroendocrine cells that coordinate female reproductive behaviour (Van Kesteren et al 1995b.…”

“…In the lumbricid earthworm Eisenia foetida, an OT-related peptide termed 'annetocin' has also been characterized (Oumi et al 1994. In annelids, annetocin induces egg laying, which is accompanied by secretion of mucus from the clitellum (Ukena et al 1995). However, little information is currently available on OT/AVP-related receptors in this phylum.…”

Development of the γ-amino butyric acid (GABA)-ergic signaling system and its role in larval swimming in sea urchin

“…Interaction between nervous systems involved in larval swimming regulation and the GABAergic system GABA and dopamine are regarded as being excitatory signals in invertebrates, whereas serotonin is inhibitory (Ukena et al, 1995). Thus, they can act in a complementary manner to regulate ciliary beating, and hence larval swimming.…”

GABA-immunoreactive neurons in the central and peripheral nervous system of the earthworm, Lumbricus terrestris (Oligochaeta, Annelida)

“…Others (Tashiro and Kuriyama 1977;Gardner and Walker 1982) claim that this effect is only inhibitory. Initially, this amino acid was shown to inhibit gut peristalsis (McIntire et al 1993); however, Ukena et al (1995) have subsequently reported an excitatory effect.…”