Learned helplessness increases 5-hydroxytryptamine1B receptor mRNA levels in the rat dorsal raphe nucleus.
Learned helplessness is a behavioral condition induced by exposure to inescapable stress that models aspects of stress-related disorders including depression and posttraumatic stress disorder, and has been associated with diminished serotonin release in the rat frontal cortex. Our hypothesis was that presynaptic 5-hydroxytryptamine1B (5-HT1B) receptors, which inhibit the synthesis and release of serotonin in nerve terminals, may be increased in learned helplessness. Postsynaptic 5-HT1B mRNA hybridization levels in the hippocampus or frontal cortex were unchanged following induction of learned helplessness; however, presynaptic 5-HT1B mRNA hybridization signal in the dorsal raphe nucleus of helpless rats was 25% higher than control values. There was no change in dorsal raphe serotonin transporter mRNA level. The detection of increased 5-HT1B mRNA levels in the dorsal raphe nucleus suggests an increased capacity to synthesize presynaptic 5-HT1B receptors and could account for diminished serotonin neurotransmission in learned helplessness.
Neumaier
J F
JF
Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, USA.
Petty
F
F
Kramer
G L
GL
Szot
P
P
Hamblin
M W
MW
D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D003720:Densitometry; D006380:Helplessness, Learned; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D017403:In Situ Hybridization; D008297:Male; D017966:Pyramidal Cells / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis*; D011903:Raphe Nuclei / Q000378:metabolism*; D051381:Rats; D011985:Receptors, Serotonin / Q000096:biosynthesis*
D012333:RNA, Messenger; D011985:Receptors, Serotonin