Many of the features in the ontogeny of behavior are common to all animals with a central nervous system. For instance, spontaneous coordinated movements appear before reflexes can be elicited in many animals, from insects and annelids through frogs, chicks and humans. The spontaneity has been attributed to the establishment of interneuronal connections to motor neurons before the sensory to interneuronal connections form. By using a relatively simple animal, the leech, in which both the structure and function of individual neurons has been well characterized, and which has a nervous system that is accessible for cellular studies throughout development, we can determine the cellular basis for such behavioral observations. We propose to study the neuronal basis for the development of two leech behaviors, reflex shortening and swimming. Using intracellular microelectrodes, we will record from identified sensory neurons, interneurons and motor neurons when these behavioral acts appear and are elaborated. We will characterize their individual electrical properties, particularly their ability to generate action potentials. We will also determine when they first make synaptic contacts, and follow the progress of the synaptic properties until they acquire all their adult-like features. In addition, we will fill the neurons with dyes, to characterize at both the light and electron microscopic levels the outgrowth of the neuronal processes and the ways in which processes of different cells come together to make synapses. Once we know the normal order of developmental events, we will perturb that order by cutting nerves, ablating target tissues, and by killing individual neurons to establish the rules by which neurons connect to one another to form circuits responsible for producing behavior. Hopefully, these studies will provide insight into the behavioral development of other animals, and will also provide a basis for studying the molecular mechanisms for the formation and maintenance of synapses in the development of behavior.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS020746-02
Application #
3401307
Study Section
Neurology B Subcommittee 1 (NEUB)
Project Start
1984-12-01
Project End
1987-11-30
Budget Start
1985-12-01
Budget End
1986-11-30
Support Year
2
Fiscal Year
1986
Total Cost
Indirect Cost
Name
University of California San Diego
Department
Type
Schools of Arts and Sciences
DUNS #
077758407
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Loer, C M; Kristan Jr, W B (1989) Central synaptic inputs to identified leech neurons determined by peripheral targets. Science 244:64-6
Loer, C M; Kristan Jr, W B (1989) Peripheral target choice by homologous neurons during embryogenesis of the medicinal leech. I. Segment-specific preferences of Retzius cells. J Neurosci 9:513-27
Loer, C M; Kristan Jr, W B (1989) Peripheral target choice by homologous neurons during embryogenesis of the medicinal leech. II. Innervation of ectopic reproductive tissue by nonreproductive Retzius cells. J Neurosci 9:528-38
Jellies, J; Kristan Jr, W B (1988) Embryonic assembly of a complex muscle is directed by a single identified cell in the medicinal leech. J Neurosci 8:3317-26
Jellies, J; Kristan Jr, W B (1988) An identified cell is required for the formation of a major nerve during embryogenesis in the leech. J Neurobiol 19:153-65
Glover, J C (1987) Serotonin storage and uptake by identified neurons in the leech Haementeria ghilianii. J Comp Neurol 256:117-27
Loer, C M; Jellies, J; Kristan Jr, W B (1987) Segment-specific morphogenesis of leech Retzius neurons requires particular peripheral targets. J Neurosci 7:2630-8
Jellies, J; Loer, C M; Kristan Jr, W B (1987) Morphological changes in leech Retzius neurons after target contact during embryogenesis. J Neurosci 7:2618-29
Glover, J C; Mason, A (1986) Morphogenesis of an identified leech neuron: segmental specification of axonal outgrowth. Dev Biol 115:256-60
Loer, C M; Schley, C; Zipser, B et al. (1986) Development of segmental differences in the pressure mechanosensory neurons of the leech Haementeria ghilianii. J Comp Neurol 254:403-9