The pond snail, Lymnaea stagnalis (L.), is an excellent system for studying integrative mechanisms underlying behaviour. For example, respiratory behaviour clearly consists of several locomotory reactions, shell movements, erection of the pneumostome and ventilation of the lung. Respiration is regulated by the oxygen content of the water, food, sex arousal, defensive behaviour and is seasonally modulated. The network controlling respiration modulates the neural ensembles underlying the component behaviours and vice versa. Our findings show that neurones controlling locomotion are connected to neurones of the cardiovascular and locomotory systems.

With respect to respiratory behaviour, it is known that three identified neurones make up the central respiratory generator (CRG) and their synaptic connections have been reconstructed in cell culture. A number of respiratory motor neurones have also been identified. During lung ventilation, both ciliary beating and muscular movements associated with locomotion are inhibited due to synaptic inputs from the CRG. Both direct and indirect connections from the CRG to heart motor neurones exist, but details of cardiorespiratory integration are as yet unclear. Thus neurones controlling the respiratory system lie within and interact with a complex neuronal network underlying several behaviours.