Divergent effects of putative anxiolytics on stress-induced fos expression in the mesoprefrontal system of the rat.
Previously, we reported that R(+)HA-966, a weak partial agonist for the glycine/NMDA receptor, and guanfacine, a noradrenergic alpha2 agonist, have anxiolytic-like actions on the biochemical activation of the mesoprefrontal dopamine neurons and fear-induced behaviors. Here, we examined these two putative anxiolytic agents, both with primary actions independent of GABAergic systems, for their ability to alter stress-induced Fos-like immunoreactivity in the mesoprefrontal cortex and in tyrosine hydroxylase-stained, presumed dopaminergic, neurons in the ventral tegmental area. The benzodiazepine agonist, lorazepam, and partial agonist, bretazenil, were also tested in this footshock paradigm [10 x 0.5 sec, 0.8 mA paired with a 5-sec tone]. In saline-treated rats, footshock resulted in an increase in Fos-li in the prelimbic and infralimbic cortices and tyrosine hydroxylase-labeled cells in the ventral tegmental area. Treatment with lorazepam or bretazenil prevented the stress-induced activation in Fos-li nuclei in all regions of the medial prefrontal cortex and in dopaminergic neurons in the ventral tegmental area. In contrast, the actions of the novel anxiolytic-like agents on stress-induced Fos-li were different than those observed with benzodiazepine agonists. Both putative anxiolytics, R(+)HA-966 and guanfacine, did not reduce, but significantly enhanced the stress-induced Fos-li in the prelimbic region of the medial prefrontal cortex. Additionally, treatment with R(+)HA-966 completely blocked, while guanfacine attenuated, the stress-induced increase in the number of Fos-li, TH-li cells in the ventral tegmental area. These results indicate that the putative anxiolytics, R(+)HA-966 and guanfacine, have actions on the stress-sensitive mesoprefrontal system which appear distinct from those of traditional anxiolytics.
Morrow
B A
BA
Department of Pharmacology, Laboratory of Neuropsychopharmacology, Yale University School of Medicine, New Haven, Connecticut 06520-8066, USA. bret.morrow@yale.edu
Elsworth
J D
JD
Lee
E J
EJ
Roth
R H
RH
D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D003213:Conditioning, Psychological / Q000502:physiology; D004298:Dopamine / Q000378:metabolism; D008297:Male; D009434:Neural Pathways / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D017397:Prefrontal Cortex / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013312:Stress, Physiological / Q000503:physiopathology*; D017557:Ventral Tegmental Area / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*
D014151:Anti-Anxiety Agents; D016760:Proto-Oncogene Proteins c-fos; D004298:Dopamine