Dopamine elicits feeding motor program in Limax maximus

Abstract

A neural system within the cerebral and buccal ganglia of the terrestrial mollusc Limax maximus responds to lip chemostimulation by emitting a feeding motor program (FMP) in uiuo and in uitro. We have analyzed chemically the cerebral and buccal ganglia of Limax for neurotransmitters involved in controlling expression of FMP. Dopamine was found in clusters of cells and in the neuropil of the cerebral ganglia at a concentration of 62 pmol/ganglion; a large proportion of such dopamine-containing cells projected to the lips. The buccal ganglia contained several small dopaminergic cells and large amounts of dopamine in the neuropil; the measured concentration was 10 pmol/ganglion.Exogenous dopamine applied to the cerebral and buccal ganglia in vitro between lop7 M and 3 x lop6 M excited an autoactive salivary duct motor neuron (FB) and inhibited an autoactive secretomotor neuron (BSN). Concentrations of dopamine between 3 X 10m6 M and 3 X 10e5 M triggered FMP output, with an increased probability of triggering at higher concentrations of dopamine. ADTN and SK&F38393 were potent agonists in this system, whereas ergonovine was the only potent antagonist found; none of the neuroleptics tested was effective. Thus, the Limax system shows agonist responses similar to the vertebrate Dl receptors, but its antagonist-binding properties appear to have requirements quite different from vertebrate receptors.The effects of exogenous serotonin differed from dopamine's effects; serotonin excited BSN and several buccal motor neurons, could not elicit synchronized motor program cycling, and was not efficiently blocked by ergonovine.These data suggest that dopamine is a good candidate as an endogenous triggering and sustaining transmitter for the Limax feeding motor program.

Cerebral CBm1 Neuron Contributes to Synaptic Modulation Appearing During Rejection of Seaweed inAplysia kurodai

“…The MCC neurons receive chemosensory and mechanosensory inputs from the head region including the lips and the MCC activity contributes to the progressive enhancement of the rate and magnitude of the biting responses that characterizes food-induced arousal (Rosen et al 1982;Weiss et al 1978Weiss et al , 1986a. In some gastropods, the application of dopamine to the CNS has been reported to evoke the buccal motor program thought to represent fictive feeding (Kabotyanski et al 2000;Kyriakides and McCrohan 1989;Teyke et al 1993;Trimble and Barker 1984;Wieland and Gelperin 1983). The studies for the dopamine neurotoxin (Kemenes et al 1990) and for the development of the dopamine-containing neurons (Voronezhskaya et al 1999) also support the contribution of dopamine to the generation of the feeding motor program.…”

Waves and stimulus-modulated dynamics in an oscillating olfactory network.

“…PC lobes are removed from 1-to 5-g animals that are hatched and raised in a controlled environment (17 The average voltage change in the field of each detector or charged-coupled device element is linearly proportional to the fractional change in the measured emission-i.e., AV(x, y, t) a -AF(x, y, t)/F(x, y), where F(x, y, t) is the intensity of emitted light measured at time t by a detector whose field of view is centered at (x, y), AF(x, y, t) = F(x, y, t) -F(x, y), and F(x, y) = (1/T)X,F(x, y, t) with Tequal to the number of frames in the sequence. Images of the change in potential inferred from the change in emission are presented as successive two-dimensional spatial maps of -AF/F.…”

Animal Foraging and the Evolution of Goal-Directed Cognition

“…In mollusks and crustaceans, dopamine modulates the control of pattern-generating interneurons associated with movement (Harris-Warrick, Coniglio, Barazangi, Guckenheimer, & Gueron, 1995), and in the lobster stomatogastric ganglion this is known to be directly mediated through glutamate (Cleland & Selverston, 1997;Johnson & Harris-Warrick, 1997). Dopamine also modulates various aspects of feeding in Aplysia (Due, Jing, & Klaudiusz, 2004;Kabotyanski, Baxter, Cushman, & Byrne, 2000) and the gastropod mollusks Helisoma, Lymnaea, and Limax maximus (Elliott & Vehovszky, 2000;Trimble & Barker, 1984;Wieland & Gelperin, 1983). Dopamine induces the salivary response of the cockroach, Periplaneta americana (Baumann, Dames, Kühnel, & Walz, 2002), and other insects (see Nassel, 1996).…”