|
| Norman
T. Davis |
 |
Research
Professor
Ph.D., University of Wisconsin, 1954
|
| Office:
|
Gould-Simpson
Bldg. Rm. 612 |
| Email: |
ntd@neurobio.arizona.edu |
| Phone: |
(520) 626-7087 |
| Fax: |
(520) 621-8282 |
| |
Insect
Neuroanatomy and Neuroendocrinology
In
insects the endocrine system is a part of the nervous system.
Specialized neurons release neurohormones that regulate various
processes such as development, homeostasis, excretion, heart
activity, digestion, and reproduction. In addition, these neurohormones
may be involved in the initiation of certain behaviors such
as ecdysis, feeding, flight, and mating. The neurohormones
are mostly peptides and many of them have been isolated and
identified, providing a rich opportunity for the study of their
functions. We have been studying the neuroendocrine system
of insects, using Manduca sexta as a model. In these studies we use various methods, such as immunocytochemistry,
neuronal tracing, microsurgery, bioassays, and organ transplantation
and ablations. Our recent work on the neuroendocrine system
includes studies of neurons that control photoperiodic induction
of pupal diapause. We have found that these neurons express
the clock protein PER and the neurohormone corazonin. These
results suggest that photoperiodism relies on a clock-like
mechanism and may be mediated by corazonin, and we plan to
explore these possibilities.
The
same neuropeptides that are released as hormones are also found
in many interneurons and are released into the CNS as paracrine
factors. Very little is known of their function, but evidence
from other animal models indicate that they modulate neuronal
excitability, and thus effect behavior. In some instances paracrine
release of certain neuropeptides appears to be a broadly distributed,
and we believe that this type of release may be involved a
general up or down regulation of the responsiveness of the
CNS, as in states of quiescence arousal. Recently we have identified
a single pair of peptidergic interneurons that project to all
parts of the CNS of the larvae larva of M. sexta, and we believe these neurons may be an ideal model for studying neuromodulation
in insects. Using techniques of immunocytochemistry and targeted
cell ablation, we hope to determine the function of these interneurons.
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Selected
Recent Publications
Davis NT, Hildebrand JG. Feb 2006. Neuroanatomy of the sucking pump of the moth, Manduca sexta (Sphingidae, Lepidoptera). Arthropod Struct Dev, 35:15-33
Shiga S, Davis NT, Hildebrand JG. Jun 2003. Role of neurosecretory cells in the photoperiodic induction of pupal diapause of the tobacco hornworm Manduca sexta. J Comp Neurol, 462:275-85
Davis NT, Blackburn MB, Golubeva EG, Hildebrand JG. May 2003. Localization of myoinhibitory peptide immunoreactivity in Manduca sexta and Bombyx mori, with indications that the peptide has a role in molting and ecdysis. J Exp Biol, 206:1449-60
Wise S, Davis NT, Tyndale E, Noveral J, Folwell MG, Bedian V, Emery IF, Siwicki KK. Jun 2002. Neuroanatomical studies of period gene expression in the hawkmoth, Manduca sexta. J Comp Neurol, 447:366-80
Dulcis D, Davis NT, Hildebrand JG. Dec 2001. Neuronal control of heart reversal in the hawkmoth Manduca sexta. J Comp Physiol [A], 187:837-49
Davis NT, Dulcis D, Hildebrand JG. Nov 2001. Innervation of the heart and aorta of Manduca sexta. J Comp Neurol, 440:245-60
Davis NT, Veenstra JA, Feyereisen R, Hildebrand JG. Aug 1997. Allatostatin-like-immunoreactive neurons of the tobacco hornworm, Manduca sexta, and isolation and identification of a new neuropeptide related to cockroach allatostatins. J Comp Neurol, 385:265-84
Displaying 1 - 7 of 23
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