Ke. Scrogin et al., Multiple receptor subtypes mediate the effects of serotonin on rat subfornical organ neurons, AM J P-REG, 44(6), 1998, pp. R2035-R2042
Citations number
41
Categorie Soggetti
Physiology
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY
The subfornical organ (SFO) receives significant serotonergic innervation.
However, few reports have examined the functional effects of serotonin on S
FO neurons. This study characterized the effects of serotonin on spontaneou
sly firing SFO neurons in the rat brain slice. Of 31 neurons tested, 80% re
sponded to serotonin (1-100 mu M) with either an increase (n = 15) or decre
ase (n = 10)in spontaneous activity. Responses to serotonin were dose depen
dent and persisted after synaptic blockade. Excitatory responses could also
be mimicked by the 5-hydroxytryptamine (5-HT)(2A/2C) receptor agonist 2,5-
dimethoxy-4-iodoamphetamine (DOI; 1-10 mu M) and could be blocked by the 5-
HT2A/2C-receptor antagonist LY-53,857 (10 mu M). LY-53,857 unmasked inhibit
ory responses to serotonin in 56% of serotonin-excited cells tested. Seroto
nin-inhibited cells were also inhibited by the 5-HT1A-receptor agonist 8-hy
droxy-2(di-n-propylamino)tetralin (8-OH-DPAT; 1-10 mu M; n = 7). The data i
ndicate that SFO neurons are responsive to serotonin via postsynaptic activ
ation of multiple receptor subtypes. The results suggest that excitatory re
sponses to serotonin are mediated by 5-HT2A or 5-HT2C receptors and that in
hibitory responses may be mediated by 5-HT1A receptors. In addition, simila
r percentages of serotonin-excited and -inhibited cells were also sensitive
to ANG II. As such the functional relationship between serotonin and ANG I
i in the SFO remains unclear.