抄録
Injection of acetylcholine into the subfornical organ (SFO) produces water intake and alterations in blood pressure. It has been suggested that the nicotinic activation of SFO neurons is related to the cadiovascular response while muscarinic activation is involved in drinking behavior as well as the cardiovascular response. If this is so, some of the neurons in the SFO should be preferentially sensitive to muscarine and others preferentially sensitive to nicotine. To investigate this possibility, we applied muscarine and nicotine to SFO neurons of rat brain slices and compared the responses using patch clamp recordings. 12 (46%) out of 21 neurons were depolarized more by muscarine than by nicotine while 9 neurons (35%) were depolarized more by nicotine than by muscarine at 10 μM in the whole-cell current-clamp mode. To elucidate the responsiveness of SFO neurons to the cholinergic agonists further, 30 neurons were tested in the whole-cell voltage-clamp mode. Muscarine and nicotine induced inward currents in the SFO neurons. At 10 μM, 23 (77%) of the 30 neurons tested were responsive to muscarine and/or nicotine. The amplitudes of the peak currents in response to muscarine were larger than those to nicotine in 13 (43%) and the responses to nicotine were greater than those to muscarine in 10 (33%). This suggests that preferential cholinergic activation through either muscarinic or nicotinic receptors in rat SFO expresses different participations in physiological functions such as drinking behavior and cadiovascular regulation. [Jpn J Physiol 54 Suppl:S199 (2004)]
