The Effect of Sex on GABAA Receptor Activation in Vasopressin Neurons from the Supraoptic Nucleus

Purpose: Arginine Vasopressin (AVP) is important in maintaining proper fluid balance and plasma osmolality. Disruption in its regulation occurs in patients with chronic heart failure (CHF) and liver failure, which leads to poorer patient outcomes. AVP neurons from the supraoptic nucleus (SON) receive input from GABA, yet it is unknown what effects GABAA receptor activation has on these neurons under pathophysiological conditions or whether the effects are sex-specific. What is known is that under pathophysiological conditions, AVP neurons are unaffected by negative feedback which leads to excessive AVP release. Understanding the role of the GABAA receptor in these conditions is important. Here, we investigate whether activation of the GABAA receptor leads to sex dependent effects. Methods: Adult, intact, Sprague Dawley rats were anesthetized and bilaterally injected with the AAV2-0VP1-ClophensorN virus directly into the SON. After a two-week recovery, the animals were sacrificed and the brains were rapidly removed. Cells from the SON were dissociated and incubated for two hours. After incubation, recordings were taken using ratiometric live cell imaging. Selected neurons were sequentially excited at 445nm and 556nm and then emission data was collected between 500-550nm and 580-653nm respectively. After 40 cycles of 3-second recordings, muscimol (100nM), a GABAA receptor agonist was transiently applied to the cells. Results: In both males and females, application of muscimol resulted in chloride influx, which implies neuronal inhibition. Conclusion: Under normal physiological conditions, GABAA receptor activation does not show sex specific effects in neurons from the SON.