The terrestrial Gastropoda Megalobulimus abbreviatus as a useful model for nociceptive experiments: effects of morphine and naloxone on thermal avoidance behavior

Abstract

We describe the behavior of the snail Megalobulimus abbreviatus upon receiving thermal stimuli and the effects of pretreatment with morphine and naloxone on behavior after a thermal stimulus, in order to establish a useful model for nociceptive experiments. Snails submitted to non-functional (22ºC) and non-thermal hot-plate stress (30ºC) only displayed exploratory behavior. However, the animals submitted to a thermal stimulus (50ºC) displayed biphasic avoidance behavior. Latency was measured from the time the animal was placed on the hot plate to the time when the animal lifted the head-foot complex 1 cm from the substrate, indicating aversive thermal behavior. Other animals were pretreated with morphine (5, 10, 20 mg/kg) or naloxone (2.5, 5.0, 7.5 mg/kg) 15 min prior to receiving a thermal stimulus (50ºC; N = 9 in each group). The results (means ± SD) showed an extremely significant difference in response latency between the group treated with 20 mg/kg morphine (63.18 ± 14.47 s) and the other experimental groups (P < 0.001). With 2.5 mg/kg (16.26 ± 3.19 s), 5.0 mg/kg (11.53 ± 1.64 s) and 7.5 mg/kg naloxone (7.38 ± 1.6 s), there was a significant, not dose-dependent decrease in latency compared to the control (33.44 ± 8.53 s) and saline groups (29.1 ± 9.91 s). No statistically significant difference was found between the naloxone-treated groups. With naloxone plus morphine, there was a significant decrease in latency when compared to all other groups (minimum 64% in the saline group and maximum 83.2% decrease in the morphine group). These results provide evidence of the involvement of endogenous opioid peptides in the control of thermal withdrawal behavior in this snail, and reveal a stereotyped and reproducible avoidance behavior for this snail species, which could be studied in other pharmacological and neurophysiological studies.

The effect of opioids and their antagonists on the nocifensive response of Caenorhabditis elegans to noxious thermal stimuli

“…Exposure to the antagonists was done 15 min prior to the exposure to the agonists. These concentrations are consistent with those used for morphine and naloxone in other invertebrates studies (Achaval et al 2005; Zabala and Gomez 1991). Times and mode of exposure used were also consistent with those used for C. elegans in similar studies (Wittenburg and Baumeister 1999).…”

“…Opioids play an important role in modulating nociception. The effect of morphine on the behavioral response of invertebrates to aversive stimuli is documented in the literature (Achaval et al 2005; Barr et al 2008; Kalil-Gaspar et al 2007; Kavaliers et al 1983, 1998; Lozada et al 1988; Maldonado et al 1989; Pryor et al 2007; Romano et al 1990; Romero et al 1994). In all instances, morphine increases the latency response of the animals.…”

Symptoms of behavioural anapyrexia – Reverse fever as a defence response of snails to fluke invasion

“…Snails possess this ability, as the observations of various authors can testify (Kavaliers et al, 1983;Kavaliers and Hirst, 1986;Marshall et al, 2010). Depending on the intensity and direction of the thermal stimulus these animals react behaviourally, increasing or decreasing exposure to specific temperature conditions (Muñoz et al, 2005;Achaval et al, 2005). Lefcort and Bayne (1991) observed changes in the thermal behaviour of B. glabrata exposed to miracidia of S. mansoni, and earlier Cabanac and Rossetti (1987) investigated the thermal preferences of Lymnaea auricularia (=Radix auricularia) after the injection of bacterial pyrogenic factors.…”

Monoamines in the pedal plexus of the land snail Megalobulimus oblongus (Gastropoda, Pulmonata)

“…Though the principal means of locomotion in M. oblongus is the wave movement of the pedal musculature along the ventral surface of the foot, the ciliated epithelium and the 5-HT mesh may also be partially involved in the foot movement, given that the forces of the muscular waves are coupled to the substrate by a thin layer of pedal mucus (3). 5-HT injection prior to thermal aversive stimulation produced a strong increase in mucus secretion in the ventral zone of the foot of M. oblongus (10). This finding suggests a serotonergic involvement in the mucus secretion of the integument.…”

“…In a pharmacological review of rhythmic behaviors such as locomotion or breathing, the modulatory role of 5-HT is noteworthy in the control of locomotion (8,10) and feeding (11)(12)(13), while dopamine has been reported to play a role in breathing (14). In addition, the modulatory role of 5-HT in aversive behavior (10,15) has also been documented (16).…”