Functional correlates of activity in neurons projecting from the lamina terminalis to the ventrolateral periaqueductal gray.
The lamina terminalis (LT) consists of the organum vasculosum of the LT (OVLT), the median preoptic nucleus (MnPO) and the subfornical organ (SFO). All subdivisions of the LT project to the ventrolateral periaqueductal gray (vlPAG). The LT and the vlPAG are implicated in several homeostatic and behavioral functions, including body fluid homeostasis, thermoregulation and the regulation of sleep and waking. By combining visualization of c-Fos protein and retrograde neuroanatomical tracer we have examined the functional correlates of LT-vlPAG projection neurons. Rats were injected with retrograde tracer into the vlPAG and, following a 1-week recovery period, they were subjected to either hypertonic saline administration (0.5 M NaCl, 1 mL/100 g i.p.), 24-h water deprivation, isoproterenol administration (increases circulating angiotensin II; 50 microg/kg s.c.), heat exposure (39 degrees C for 60 min) or permitted 180 min spontaneous sleep. Retrogradely labeled neurons from the vlPAG and double-labelled neurons were then identified and quantified throughout the LT. OVLT-vlPAG projection neurons were most responsive to hypertonic saline and water deprivation. SFO-vlPAG projection neurons were most active following isoproterenol administration, and MnPO-vlPAG projection neurons displayed significantly more Fos immunostaining following water deprivation, heat exposure and sleep. These results support the existence of functional subdivisions of LT-vlPAG-projecting neurons, and indicate three patterns of activity that correspond to thermal and sleep wake regulation, osmotic or hormonal stimuli.
Uschakov
Aaron
A
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA. Aaron.Uschakov@unige.ch
McGinty
Dennis
D
Szymusiak
Ronald
R
McKinley
Michael J
MJ
D000804:Angiotensin II / Q000097:blood / Q000378:metabolism; D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology; D002316:Cardiotonic Agents / Q000494:pharmacology; D006706:Homeostasis / Q000502:physiology*; D006358:Hot Temperature; D007031:Hypothalamus / Q000166:cytology / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D056325:Neuronal Tract-Tracers; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D010487:Periaqueductal Gray / Q000166:cytology / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012462:Saline Solution, Hypertonic / Q000378:metabolism; D012890:Sleep / Q000502:physiology; D014868:Water Deprivation / Q000502:physiology; D014882:Water-Electrolyte Balance / Q000502:physiology
D002316:Cardiotonic Agents; D056325:Neuronal Tract-Tracers; D016760:Proto-Oncogene Proteins c-fos; D012462:Saline Solution, Hypertonic; D000804:Angiotensin II; D007545:Isoproterenol