The goal of this study is to characterize the influence of atrial receptors on the activity of vasopressin (AVP) and oxytocin (OXY) neurons in the supraoptic nucleus (SON) of anaesthetized rats. Atrial receptors were stimulated using a balloon catheter placed at the junction of the vena cava and the right atria (Kaufman 1984). Five adult male Sprague-Dawley rats were anaesthetized with pentobarbital (50 mg/kg i.p followed by supplemental i.v. injections of 2-5 mg) and prepared for extracellular recording from SON neurons using a transpharyngeal approach. Neurons were antidromically activated using a bipolar electrode placed in the posterior pituitary and characterized as either AVP or OXY based on their pattern of spontaneous activity and their response to an increase in blood pressure produced by a bolus injection of phenytophrine (10 μg/10 μl i.v.). AVP neurons are either phasically or continuously active and are inhibited by increases in blood pressure. OXY neurons are continuously active but they are not influenced by blood pressure elevations. A majority of the AVP neurons (7 out of 8 cells) showed significant decreases in activity associated with inflation of the balloon with an average decrease in activity of 57% (p<0.05). The remaining AVP cell was not effected. A majority of the OXY neurons were activated by atrial receptor stimulation (3 out of 5 cells) with an average increase in activity of 64%. These results suggest that the activity of AVP and OXY neurons in the SON are differentially regulated by atrial receptors in the rat.
|State||Published - 20 Mar 1998|