Acute electrical stimulation of the subfornical organ induces feeding in satiated rats

The SFO, a circumventricular organ (CVO) that lacks the normal blood-brain barrier, is an important site in central autonomic regulation. A role for the SFO in sensing circulating satiety signals has been suggested by electrophysiological studies demonstrating that the anorexigenic satiety signals, leptin and amylin, as well as the orexigenic satiety signal, ghrelin, influence the excitability of separate populations of SFO neurons. The present study examined whether acute, short duration, electrical stimulation of the SFO influenced feeding in satiated rats. Electrical stimulation (200 microA) of satiated animals with subfornical organ (SFO) electrode placement (n=6) elicited feeding in all animals tested with a mean latency to eat of 8.0+/-4.0 min after termination of SFO stimulation (mean food consumption: 0.6+/-0.12 g/100g bw). These same rats undergoing a sham stimulation did not eat (mean food consumption: 0.0+/-0.0 g, n=6) nor did animals receiving stimulation with non-SFO electrode placements (mean food consumption: 0.0+/-0.0 g, n=6). SFO stimulation at this intensity elicited drinking in 5/6 animals with a mean latency to drink of 15.2+/-2.6 min. Feeding effects were specific to higher stimulation intensities as lower intensity stimulation (100 microA, n=6) elicited drinking (mean latency to drink: 6.2+/-2.6 min) but did not cause any animal to eat. The results of the present study show that acute, short duration, SFO stimulation induces feeding in satiated rats, lending support for a role for the SFO as an integrator of circulating peptides that control feeding.