[Abstract Title]. - Society for Neuroscience

Poster
282. Stress and the Brain: Cellular Actions of Stress
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 282.6/OO13
Topic: E.06.d. Cellular actions of stress
Support: MH075047 to Beck
MH067651 to Bhatnagar
ONR NN0014-03-1-0311 to Beck
Title: Orexin alters firing pattern of neurons in the posterior paraventricular thalamus (pPVTh)
after repeated stress
Authors: *S. BHATNAGAR, D. PIEHL, V. IYER, S. BECK;
Dept Anesthesiol., Univ. Pennsylvania, Children's Hosp Philadelphia, Philadelphia, PA
Abstract: Our previous work suggests that activation of pPVTh neurons primarily inhibits
neuroendocrine and behavioral responses in repeatedly stressed compared to control or acutely
stressed rats. Interestingly, the PVTh receives dense orexin inputs from cell bodies in the lateral
hypothalamus and pPVTh cells contain the two orexin receptor subtypes. Since orexin is a
peptide important for arousal and attention, we hypothesized that orexin inputs to the pPVTh are
important for regulating responsivity in repeatedly stressed rats. In a related abstract, we show
that blockade of orexin receptors in the pPVTh attenuates ACTH responses to acute restraint in
rats exposed to repeated swim but not in acutely restrained rats. Here, we examined the effects of
orexin administration on pPVTh neurons at a cellular level and hypothesized that the response of
pPVTh cells to orexin would be different in control and repeatedly stressed rats. We exposed rats
to no stress or to 4 days of repeated swim for 15min per day. On day 5, we obtained 200 micron
thick brain slices containing the pPVTh. Whole cell recordings were used to record from pPVTh
neurons. Cell characteristics were measured using current clamp. Stress did not alter the resting
membrane potential, resistance or time constant of the neurons. However, the firing pattern of
the cells was different. The cells from the control rats exhibited primarily a bursting firing
pattern, whereas the majority of the cells from the swim stressed rats did not exhibit any firing.
Orexin (100 nM) was bath applied for 3 min. Preliminary results indicate that orexin induced a
greater depolarization and increase in resistance in the cells from the swim stressed rats. The
firing pattern of the cells recorded from the control rats primarily retained their bursting pattern,
whereas the cells from the swim stressed rats switched to a firing pattern of single actions. In
addition, we recorded excitatory postsynaptic potentials (EPSC) using voltage clamp techniques