Proceedings of The Physiological Society

University of Bristol (2001) J Physiol 536P, S108

Communications

Mechanisms of inhibition of feeding by a pleural interneuron in the mollusc Lymnaea stagnalis

M. Alania*†‡, D.A. Sakharov† and C.J.H. Elliott*

*Department of Biology, University of York, PO Box 373, York YO1 5YW, UK and †Laboratory of Comparative Physiology, Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilov str., Moscow, 117808 Russia; ‡Permanent address: Tbilisi State University, Faculty of Biology and Medicine, Department of Human and Animal Physiology, Laboratory of Physiology and Pathology of Brain, Chavchavadze av. 2., Tbilisi, 380028, Georgia


Pond snails (Lymnaea stagnalis) contain a single neuron, PlB, in the pleural ganglion, which contains FMRFamide (Alania & Sakharov, 1998) and is activated by inputs that cause withdrawal. To analyse the connections from the PlB to the feeding neurons, the CNS was isolated, desheathed and neurons impaled as described by Vehovszky & Elliott (2000).

The PlB interneuron has an axon that traverses the cerebral ganglia and runs into the buccal ganglia. It has neuropilar branches in the regions of the cerebral and buccal ganglia-containing feeding neurons. There is just one PlB in each pleural ganglion. Left and right PlB interneurons are coupled electrically (number of paired recordings, N = 4).

Activation of the PlB blocks fictive feeding, whether the feeding rhythm occurs spontaneously or is driven by stimulating a modulatory interneuron, including CV1 (N = 5) and SO (N = 4). The PlB inhibits the feeding system neurons, including the protraction and retraction motoneurons (N = 27), the buccal central pattern generator interneurons (N = 9), the buccal modulatory interneurons SO and OC (N = 2), and the cerebral modulatory interneurons CV1 and CGC (N = 6). All these connections persist in a Hi-Di saline, which reduces polysynaptic effects. The inhibitory effects are mimicked by application of FMRFamide at 0.1 mM (N = 8).

We conclude that this neuron provides a neural substrate for the interaction of withdrawal and feeding behaviours, explaining how withdrawal is dominant over feeding.We would like to thank The Royal Society, London, UK, The Wellcome Trust and The Russian Fund for Basic Investigations #99-04-48411 for their support.

    Alania, M. & Sakharov, D.A. (1998). Zhurnal Obshchei Biologii 59, 400-408.

    Vehovszky, A. & Elliott, C.J.H. (2000). Brain Res. 867, 188-199.

Where applicable, experiments conform with Society ethical requirements