Polysensory Interneuronal Projections to Foot Contractile Pedal Neurons in Hermissenda

• Published in: Journal of neurophysiology 2009-02, Vol.101 (2), p.824-833
• Main Authors: Crow, Terry, Tian, Lian-Ming
• Format: Article
• Language: English
• Subjects: Action Potentials - physiology; Animals; Conditioning, Psychological; Electric Stimulation - methods; Excitatory Postsynaptic Potentials - physiology; Hermissenda - physiology; Light; Locomotion - physiology; Muscle Contraction - physiology; Nerve Net - physiology; Neurons - classification; Neurons - physiology; Photoreceptor Cells, Invertebrate - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.91079.2008

Department of Neurobiology and Anatomy, University of Texas Medical School, Houston, Texas Submitted 25 September 2008; accepted in final form 1 December 2008 A Pavlovian-conditioning procedure may produce modifications in multiple behavioral responses. As an example, conditioning may result in the elicitation of a specific somatomotor conditioned response (CR) and, in addition, other motor and visceral CRs. In the mollusk Hermissenda conditioning produces two conditioned responses: foot-shortening and decreased locomotion. The neural circuitry supporting ciliary locomotion is well characterized, although the neural circuit underlying foot-shortening is poorly understood. Here we describe efferent neurons in the pedal ganglion that produce contraction or extension of specific regions of the foot in semi-intact preparations. Synaptic connections between polysensory type I b and type I s interneurons and identified foot contractile efferent neurons were examined. Type I b and type I s interneurons receive synaptic input from the visual, graviceptive, and somatosensory systems. Depolarization of type I b interneurons evoked spikes in identified tail and lateral foot contractile efferent neurons. Mechanical displacement of the statocyst evoked complex excitatory postsynaptic potentials (EPSPs) and spikes recorded from type I b and type I s interneurons and complex EPSPs and spikes in identified foot contractile efferent neurons. Depolarization of type I b interneurons in semi-intact preparations produced contraction and shortening along the rostrocaudal axis of the foot. Depolarization of I s interneurons in semi-intact preparations produced contraction of the anterior region of the foot. Taken collectively, the results suggest that type I b and type I s polysensory interneurons may contribute to the neural circuit underlying the foot-shortening CR in Hermissenda . Address for reprint requests and other correspondence: T. Crow, Department of Neurobiology and Anatomy, University of Texas Medical School, 6431 Fannin Street, Houston, TX 77030 (E-mail: terry.crow{at}uth.tmc.edu )