Abstract
The subfornical organ (SFO) is related to drinking behavior and cardiovascular response, and many SFO neurons are excited by nicotine. Nevertheless, it has been reported that central nicotinic stimulation does not seem to induce drinking behavior but cardiovascular response. To explore the discrepancy, water intake following intracerebroventricular (ICV) injection of nicotine and sensitivities for nicotine in SFO neurons were investigated in rats in detail, compared with effects of angiotensin II (ANG), which is well known as a dipsogenic material. Latency to drinking by ICV injection of nicotine at 1-100 nmol was dose-dependently shortened, but still total amount of water intakes was lower than that by ICV injections of ANG at 1-100 pmol. In extracellular recording from SFO slice preparations, 57% of SFO neurons were excited by both NIC at 30 μM and ANG at 100 nM. The neural excitation by nicotine was obviously transient while that by ANG was long-lasting. Our electrophysiological classification of dissociated SFO neurons in whole-cell patch-clamp recording showed that most nicotine-sensitive neurons were classified as F-type, a half of which showed ANG-sensitivity. These results suggest that nicotinic activation of SFO neurons is involved in a neural network of the brain triggering drinking behavior. [J Physiol Sci. 2008;58 Suppl:S114]
