Increased 5-HT2C receptor responsiveness occurs on rearing rats in social isolation.
To investigate whether isolation rearing alters 5-hydroxytryptamine2C (5-HT2C) receptors, the effect of the serotonin agonist m-chlorophenylpiperazine (mCPP) was examined on elevated plus-maze behaviour, plasma corticosterone and brain 5-HT2C receptor protein levels in rats. There was no distinction between behaviour or corticosterone levels in drug-free isolates or socially housed rats exposed to the elevated plus-maze. The anxiogenic response to mCPP (decrease in open arm entry and time and an increase in stretch attend postures) on the elevated plus-maze was greater in isolation than in socially reared controls without any concomitant difference in the hypolocomotor effect of mCPP in the two groups. mCPP produced a greater elevation in plasma corticosterone in isolates than in group-housed controls. Hippocampal 5-HT2C receptor protein-like immunoreactive levels were significantly lower following mCPP than saline only in rats reared in isolation. These results indicate that increased 5-HT2C receptor responsiveness accompanies isolation-rearing and may contribute to the enhanced response to stress and the increased neophobia seen in this animal model of trait anxiety/depression. In isolation reared rats, rapid down-regulation of supersensitive 5-HT2C receptors may occur in the hippocampus following 5-HT agonist challenge.
Fone
K C
KC
Department of Physiology and Pharmacology, Nottingham University, UK.
Shalders
K
K
Fox
Z D
ZD
Arthur
R
R
Marsden
C A
CA
D000818:Animals; D001007:Anxiety / Q000523:psychology; D001923:Brain Chemistry / Q000187:drug effects; D003345:Corticosterone / Q000097:blood; D004305:Dose-Response Relationship, Drug; D008297:Male; D011863:Radioimmunoassay; D051381:Rats; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D012934:Social Isolation; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D011985:Receptors, Serotonin; D003345:Corticosterone