Stimulation of blowfly feeding behavior by octopaminergic drugs

Abstract

Adult blowflies (Phormia regina Meigen) injected with the octopaminergic drug demethylchlordimeform (10 jug per fly) exhibited enhanced proboscis extension responses when their tarsae were touched to water or aqueous sucrose. They drank more water than saline-injected control flies did but the quantity imbibed was within the normal fluid intake capacity. They became grossly hyperphagic when offered 1 M sucrose, doubling (and in some cases even tripling) their initial body weights. Three other drugs enhanced tarsal responsiveness and induced hyperphagia: DL-octopamine, clonidine (which is known to stimulate octopaminergic receptors in insects), and pargyline, a monoamine oxidase inhibitor. Yohimbine, an antagonist of one class of octopaminergic receptor in insects, prevented the hyperphagia induced by all four drugs. Dopamine, 5-hydroxytryptamine, and DL-norepinephrine failed to cause hyperphagia. These results suggest that octopaminergic receptors in the nervous system of the blowfly positively modulate feeding and drinldng behavior.In attempting to understand the neural and chemical mechanisms by which insect feeding behavior might be regulated, we injected neuroactive drugs into hungry adult blowflies (Phormia regina Meigen) and observed subsequent feeding behavior. P. regina was chosen for our studies because a great deal is known about its responses to food stimuli and its food consumption behavior (1). We focused on two components of feeding activity: (i) responsiveness to food stimuli as indicated by proboscis extension when the tarsi of the fly were touched to dilute sucrose solutions and (ii) actual consumption of 1 M sucrose, a strong stimulus to feeding. Our results demonstrate that blowfly feeding behavior can be manipulated by specific drugs and suggest that receptors of an octopaminergic type may be involved in the regulation of feeding and drinking in these insects.MATERIALS AND METHODS P. regina larvae were reared on liver; emerging adults were held for 2 days with water available ad lib but without food. Unless otherwise noted, food-deprived adults were tested on the third day of adult life, and males and females were used indiscriminately (2).One hour prior to determination of fluid intake, flies were anesthetized with C02, weighed, and affixed to a 15-cm length of applicator stick by a droplet of warm wax applied to the dorsum of the thorax. Food consumption was estimated by holding groups of 10 flies with their tarsi in contact with 1 M sucrose or water in such a way that they could extend their mouthparts and imbibe the solution. Flies (plus attached sticks) were weighed to the nearest mg (Cahn DTL electrobalance, Cerritos, CA) shortly before presentation of the solution to be imbibed. The flies were allowed to imbibe the solution for 30 min and then were reweighed. The data obtained enabled us to calculate the amount of 1 M sucrose or water consumed by each fly. Unless otherwise noted, drugs were dissolved in 145 mM NaCl and injected into the hemocoel in a volume of 1 p1. Control fl...

Modulation of appetite and feeding behavior of the larval mosquito Aedes aegypti (L.) by the serotonin-selective reuptake inhibitor paroxetine: shifts between distinct feeding modes and the influence of feeding status.

“…For example, serotonin triggers a decrease in sucrose consumption by the blowfly Phormia regina, whereas the flesh fly Neobelliera bullata shows reduced feeding, and reduced electrophysiological responses to sensory input from sucrose receptors, following serotonin injection (Dacks et al, 2003;Long and Murdock, 1983). Serotonin depresses feeding, whereas low neuronal serotonin levels increase appetite of Drosophila larvae (Neckameyer, 2010).…”

Review of octopamine in insect nervous systems

“…[18][19][20][21] As a peripheral neuromodulator, OCT modulates the activities of skeletal and visceral muscles, other peripheral target organs including fat body, oviduct, heart, and sensory organs, and gregarization in locusts. [22][23][24][25][26] As a centrally acting neuromodulator, OCT plays a major neuromodulatory role in regulating insect behaviors, such as rhythmic behaviors in locusts, 3,27 locomotion and grooming in fruit flies, 28 dance and sting behavior in honeybees, 29,30 sensitization and dishabituation of sensory input in locusts, 31,32 discrimination of nestmates from non-nestmates in honeybees and fire ants, 33,34 feeding behaviors of blowflies, cockroaches and honeybees, [35][36][37] division of labor and foraging preference in honeybees, 38,39 conditional courtship in fruit flies, 40 visual responses in locust and honeybees, 31,[41][42][43][44] learning and memory processes in honeybees, fruit flies, and crickets, [45][46][47][48][49] and many others (Table 1).…”

Octopamine immunoreactivity in the fruit fly Drosophila melanogaster

“…It stimulates activity of the firefly light organ (Nathanson, 1979), induces flight motor activity, and acts as neurotransmitter/modulator in the locust central nervous system (CNS; Sombati and Hoyle, 1984). Octopamine regulates hormone release in cockroaches (Downer et al, 1984), induces lipid and carbohydrate metabolism in crickets (Fields and Woodring, 1991), and modulates feeding behavior of blowflies (Long and Murdock, 1983) and bees (Bicker and Menzel, 1989;Braun and Bicker, 1992). Additionally, both somatic and visceral muscles are innervated by octopaminecontaining endings in several insect species (see, e.g., Hoyle et al, 1980).…”