Cholinergic mechanism in the drinking behavior and c-fos expression in brain induced by subfornical organ stimulation in rats

The drinking behavior and the c-fos expression in rat brain induced by electrical stimulation of the subfornical organ (SFO) were examined. SFO stimulation induced stable and significant drinking behavior and Fos protein expression in 8 areas of the forebrain (organum vasculosum of the lamina terminalis, median preoptic nucleus, paraventricular nucleus, supraoptic nucleus, lateral hypothalamic area, perifornical dorsal area, substantia innominata and thalamic reuniens nucleus), and in 3 areas of the hindbrain (area postrema, solitary tract nucleus and lateral parabrachial nucleus). In certain neurons of paraventricular and supraoptic nuclei, co-expression of Fos protein and vasopressin was induced by SFO stimulation. Intracerebroventricular injection of atropine partly blocked the SFO stimulation-induced drinking behavior and the Fos protein expression in the brain, suggesting that an M-cholinergic mechanism may be involved.