Murakami DM, Fuller CA.
ASGSB Bull. 1995 Oct; 9: 42.
Section of Neurobiol., Physiol., and Behavior, Univ. of California, Davis, USA.
Our previous studies have demonstrated that chronic exposure to 2G via centrifugation results in a loss of circadian rhythm amplitude for heart rate, body temperature, and activity which recovers after ten to fourteen days. In addition, the ability of light to alter circadian rhythms is diminished. These results suggest that 2G exposure affects the pacemaker function of the suprachiasmatic nucleus (SCN) and the retino-hypothalamic tract (RHT) which is the primary visual pathway to the SCN. An important function of the RHT is to phase shift the neural pacemaker and subsequently the circadian rhythms in response to an appropriate light stimulus. Several studies have demonstrated that phase shifting light pulses induce c-Fos activity within SCN neurons. Therefore, c-Fos induction within SCN neurons has become a useful marker for RHT function. This study examined whether 2G exposure can affect the induction of cFos by a phase shifting light pulse. Rats (Sprague-Dawley) were placed in LD12:12 with food and water ad libitum. Control rats at 1G were divided into two groups. 1. Received a one hour phase shifting light pulse at CT13.5 (CLP, N=6). 2. No light pulse group (CNLP, N=6). Experimental rats were exposed to 2G for two days (when there are no circadian rhythms or effect of light pulses), and divided into two groups: 3. Received a one hour light pulse at CT13.5 (2GLP, N=6). 4. No light pulse group (2GNLP, N=6). Rats were sacrificed, prepared for histology, brain coronally sectioned at 50 um, immunohistochemically stained for c-Fos, and counterstained for Nissl. The control groups demonstrated that the CLP groups exhibited very dense c-Fos staining within the SCN relative to the CNLP group. The experimental groups demonstrated that the 2GLP group did not exhibit any significant staining for c-Fos within the SCN compared to the 2GNLP group. The lack of c-Fos staining in response to a phase shifting light pulse during 2G exposure suggests that hypergravity has a direct effect on RHT function. Whether the lack of c-Fos activity is due to gravity's effect on the retina or the SCN remains to be determined.
Publication Types:
Keywords:
- Accidents
- Animals
- Circadian Rhythm
- DNA-Binding Proteins
- Genes, fos
- Gravitation
- Hypergravity
- Hypothalamus
- Light
- Mesocricetus
- Motor Activity
- Muridae
- Rats
- Retina
- Suprachiasmatic Nucleus
- genetics
- injuries
- physiology
- NASA Discipline Number 18-10
- NASA Discipline Regulatory Physiology
- NASA Program Space Physiology and Countermeasures
- Non-NASA Center
Other ID:
UI: 102222761
From Meeting Abstracts