We plan to continue our investigation of the causes and functional consequences of dendritic regression in proleg motoneurons (MNs) in the tobacco hornworm, Manduca sexta, with these objectives: (1) to characterize anatomical and electrophysical changes in the monosynaptic connections between planta hair afferent neurons and the proleg retractor MNs during the larval-pupal transformation. This is the time during which the MNs undergo their hormonally-mediated regression and the proleg withdrawal reflex disappears. These studies will involve conventional neuronal staining techniques in combination with intracellular neuronal recordings to determine the number and strength of afferent-to-MN synapses. Possible pre- and postsynaptic causes for the weakening of the afferent-to-MN reflex will be sought. (2) To test possible causal relationships between afferent input to the MNs and MN structure, both during larval development and during the larval-pupal transformation. These experiments will involve surgical ablation of prolegs during larval life, and hormonal treatments to produce heterochronic mosaics with mixed larval and pupal attributes. Anatomical and electrophysiological studies will examine the possible causal roles of afferent synaptic input in the attainment of the larval morphology of the MN, and in the subsequent regression of the larval arbor during pupal development. (3) The final objective is to expand these studies to include interneurons (INs). Excitatory and inhibitory INs which provide monosynaptic input to the proleg MNs will be sought, and the status of these synapses during the larval-pupal period will be followed anatomically and electrophysiologically.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS023208-02
Application #
3406417
Study Section
Neurology B Subcommittee 1 (NEUB)
Project Start
1986-01-15
Project End
1988-12-31
Budget Start
1987-01-01
Budget End
1987-12-31
Support Year
2
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of California Berkeley
Department
Type
DUNS #
094878337
City
Berkeley
State
CA
Country
United States
Zip Code
94704
Hazelett, Dennis J; Weeks, Janis C (2005) Segment-specific muscle degeneration is triggered directly by a steroid hormone during insect metamorphosis. J Neurobiol 62:164-77
Kinch, Ginger; Hoffman, Kurt L; Rodrigues, Elizabeth M et al. (2003) Steroid-triggered programmed cell death of a motoneuron is autophagic and involves structural changes in mitochondria. J Comp Neurol 457:384-403
Gray, John R; Weeks, Janis C (2003) Steroid-induced dendritic regression reduces anatomical contacts between neurons during synaptic weakening and the developmental loss of a behavior. J Neurosci 23:1406-15
Weeks, Janis C (2003) Thinking globally, acting locally: steroid hormone regulation of the dendritic architecture, synaptic connectivity and death of an individual neuron. Prog Neurobiol 70:421-42
Melville, J M; Hoffman, K L; Jarrard, H E et al. (2003) Cell culture of mechanoreceptor neurons innervating proleg sensory hairs in Manduca sexta larvae, and co-culture with target motoneurons. Cell Tissue Res 311:117-30
Walters, E T; Illich, P A; Weeks, J C et al. (2001) Defensive responses of larval Manduca sexta and their sensitization by noxious stimuli in the laboratory and field. J Exp Biol 204:457-69
Wiel, D E; Wood, E R; Weeks, J C (2001) Habituation of the proleg withdrawal reflex in Manduca sexta does not involve changes in motoneuron properties or depression at the sensorimotor synapse. Neurobiol Learn Mem 76:57-80
Zee, M C; Weeks, J C (2001) Developmental change in the steroid hormone signal for cell-autonomous, segment-specific programmed cell death of a motoneuron. Dev Biol 235:45-61
Weeks, J C (1999) Steroid hormones, dendritic remodeling and neuronal death: insights from insect metamorphosis. Brain Behav Evol 54:51-60
Lubischer, J L; Verhegge, L D; Weeks, J C (1999) Respecified larval proleg and body wall muscles circulate hemolymph in developing wings of Manduca sexta pupae. J Exp Biol 202:787-96

Showing the most recent 10 out of 36 publications