Activation of 5-HT2B receptors in the medial amygdala causes anxiolysis in the social interaction test in the rat.
In a recent study, we reported the presence of neurones expressing 5-HT2B receptor protein in the medial amygdaloid nucleus of the adult rat brain. In the present study, bilateral micro-injection of the 5-HT2B receptor agonist 1-[5-(2-thienylmethoxy)-1H-3-indolyl]propan-2-amine hydrochloride (BW 723C86, 0.09 and 0.93 nmol, 5 min pretest) into the medial amygdaloid nuclei increased the total interaction time of a pair of male rats in the social interaction test, to a comparable extent to chlordiazepoxide (5 mg/kg p.o., 1 hr pretest) without altering locomotor activity; indicative of anxiolytic activity. The increase in social interaction was prevented by pretreatment with the 5-HT2C/2B receptor antagonist N-(1-methyl-5-indoyl)-N'-(3-pyridyl) urea hydrochloride (SB 200646A, at 2 but not 1 mg/kg p.o., 1 hr pretest), which did not alter behaviour when given alone. Intra-amygdala BW 723C86 (0.09, 0.31 and 0.93 nmol, 5 min pretest) did not significantly alter the number of punished responses made when the same rats were examined seven days later in a Vogel punished drinking test, although chlordiazepoxide (5 mg/kg p.o., 1 hr pretest) produced the expected anxiolytic profile. The results are consistent with the proposal that activation of 5-HT2B receptors in the medial amygdala induces anxiolysis in the social interaction model but has little effect on behaviour in a punished conflict model of anxiety. These data suggest that serotonergic neurotransmission in this nucleus may selectively affect specific kinds of anxiety generated by different animal models.
Duxon
M S
MS
Department of Physiology and Pharmacology, University of Nottingham, Medical School, Queen's Medical Centre, U.K.
Kennett
G A
GA
Lightowler
S
S
Blackburn
T P
TP
Fone
K C
KC
D000679:Amygdala / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001007:Anxiety / Q000139:chemically induced* / Q000523:psychology*; D004327:Drinking Behavior / Q000187:drug effects; D007211:Indoles / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology; D008297:Male; D008845:Microinjections; D011678:Punishment; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D012919:Social Behavior; D013876:Thiophenes / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology; D014508:Urea / Q000031:analogs & derivatives / Q000494:pharmacology
C092430:1-(5-(2-thenyloxy)-1H-indol-3-yl)propan-2-amine; D007211:Indoles; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D013876:Thiophenes; C080864:N-(1-methyl-5-indolyl)-N'-(3-pyridyl)urea; D014508:Urea