Fritzsch B, Bruce LL.
ASGSB Bull. 1995 Oct; 9: 97.
Dept. of Biomedical Sciences, Creighton University, Omaha, NE, USA.
Deficits in behavioral orientation have been observed in chicks and rats reared in microgravity, suggesting that microgravity may induce the growth of anomalous neuronal connections between the vestibular sensory epithelium and the motor system. We are currently analyzing the projections from the gravistatic sensory epithelia of the inner ear, the utricle and saccule, to the central nervous system in rats flown from gestation day 9 to 20 on the STS-66 flight. Thus far we have analyzed 4 synchronous control- and 4 microgravity exposed fetal rats. Small amounts of the lipophylic dye, DiI, were inserted into the utricle (left side) and saccule (right side). Analysis of the projection patterns yielded 2 interesting results. First, in the microgravity-exposed fetuses, the facial sensory neurons had exuberant branches to the utricle that were virtually absent in the controls. Examination of controls revealed that one fetus had 3 labeled facial neurons and the other 3 had none. However, between 7 and 15 neurons were labeled in the facial sensory ganglion of each of the mg-exposed fetuses. Second, the utricular and saccular axons of controls had elaborate branching patterns throughout all vestibular nuclei, characterized by axons with multiple branches, short side branches and synapse-like swellings. In contrast, axons in 3 of 4 microgravity-exposed fetuses were largely unbranched, generally ending in growth cones. Projections to rostral targets (e.g., superior vestibular nucleus and cerebellum) covered smaller areas than those of the controls. The projections of the fourth microgravity-exposed fetus could not be distinguished from controls. This preliminary data suggests that gravity may play an important role in establishing functional connections in the vestibular system; its absence may cause a delay in the vestibular development. However, this data may also reflect random variation and further analysis is necessary before reaching any conclusions.
Publication Types:
Keywords:
- Animals
- Axons
- Cerebellum
- Ear, Inner
- Fetus
- Gravitation
- Muridae
- Neurons
- Neurons, Afferent
- Rats
- Rats, Sprague-Dawley
- Saccule and Utricle
- Synapses
- Vestibular Nuclei
- Weightlessness
- NASA Discipline Developmental Biology
- NASA Discipline Number 00-00
- NASA Program Flight
- Non-NASA Center
Other ID:
UI: 102222743
From Meeting Abstracts