Seung Won Lee

Chronic Hyperosmotic Stress Converts GABAergic Inhibition into Excitation in Vasopressin and Oxytocin Neurons in the Rat

In mammals, the increased secretion of arginine–vasopressin (AVP) (antidiuretic hormone) and oxytocin (natriuretic hormone) is a key physiological response to hyperosmotic stress. In this study, we examined whether chronic hyperosmotic stress weakens GABAA receptor-mediated synaptic inhibition in rat hypothalamic magnocellular neurosecretory cells (MNCs) secreting these hormones. Gramicidin-perforated recordings of MNCs in acute hypothalamic slices prepared from control rats and ones subjected to the chronic hyperosmotic stress revealed that this challenge not only attenuated the GABAergic inhibition but actually converted it into excitation. The hyperosmotic stress caused a profound depolarizing shift in the reversal potential of GABAergic response (EGABA) in MNCs. This EGABA shift was associated with increased expression of Na+–K+–2Cl− cotransporter 1 (NKCC1) in MNCs and was blocked by the NKCC inhibitor bumetanide as well as by decreasing NKCC activity through a reduction of extracellular sodium. Blocking central oxytocin receptors during the hyperosmotic stress prevented the switch to GABAergic excitation. Finally, intravenous injection of the GABAA receptor antagonist bicuculline lowered the plasma levels of AVP and oxytocin in rats under the chronic hyperosmotic stress. We conclude that the GABAergic responses of MNCs switch between inhibition and excitation in response to physiological needs through the regulation of transmembrane Cl− gradients.

The efficacy of Imagery Rescripting (IR) for social phobia: A randomized controlled trial

BACKGROUND AND OBJECTIVES There is a need for brief effective treatment of social phobia and Imagery Rescripting (IR) is a potential candidate. The purpose of this study was to examine the efficacy of IR preceded by cognitive restructuring as a stand-alone brief treatment using a randomized controlled design. METHODS Twenty-three individuals with social phobia were randomly assigned to an IR group or to a control group. Participants in the IR group were provided with one session of imagery interviewing and two sessions of cognitive restructuring and Imagery Rescripting. Those in the control group had one session of clinical interviewing and two sessions of supportive therapy. Outcome measures including the Korean version of the social avoidance and distress scale (K-SADS) were administered before and after treatment, and at three-month follow-up. The short version of the Questionnaire upon Mental Imagery and the Traumatic Experience Scale were also administered before treatment. RESULTS Participants in the IR group improved significantly on K-SADS and other outcome measures, compared to the control group. The beneficial effects of IR were maintained at three-month follow-up. It was also found that mental imagery ability and the severity of the traumatic experience did not moderate the outcome of IR. LIMITATIONS Further studies are needed to replicate the findings of our study using a large sample. CONCLUSIONS The efficacy of IR as a stand-alone brief treatment was demonstrated for social phobia. The findings indicate that IR could be utilized as a cost-effective intervention for social phobia.

GABAergic Excitation of Vasopressin Neurons Possible Mechanism Underlying Sodium-Dependent Hypertension

Rationale: Increased arginine-vasopressin (AVP) secretion is a key physiological response to hyperosmotic stress and may be part of the mechanism by which high-salt diets induce or exacerbate hypertension. Objective: Using deoxycorticosterone acetate-salt hypertension model rats, we sought to test the hypothesis that changes in GABAA receptor–mediated inhibition in AVP-secreting magnocellular neurons contribute to the generation of Na+-dependent hypertension. Methods and Results: In vitro gramicidin-perforated recordings in the paraventricular and supraoptic nuclei revealed that the GABAergic inhibition in AVP-secreting neurons was converted into excitation in this model, because of the depolarization of GABA equilibrium potential. Meanwhile, in vivo extracellular recordings in the supraoptic nuclei showed that the GABAergic baroreflexive inhibition of magnocellular neurons was transformed to excitation, so that baroreceptor activation may increase AVP release. The depolarizing GABA equilibrium potential shift in AVP-secreting neurons occurred progressively over weeks of deoxycorticosterone acetate-salt treatment along with gradual increases in plasma AVP and blood pressure. Furthermore, the shift was associated with changes in chloride transporter expression and partially reversed by bumetanide (Na+-K+-2Cl– cotransporter inhibitor). Intracerebroventricular bumetanide administration during deoxycorticosterone acetate-salt treatment hindered the development of hypertension and rise in plasma AVP level. Muscimol (GABAA agonist) microinjection into the supraoptic nuclei in hypertensive rats increased blood pressure, which was prevented by previous intravenous V1a AVP antagonist injection. Conclusions: We conclude that the inhibitory-to-excitatory switch of GABAA receptor–mediated transmission in AVP neurons contributes to the generation of Na+-dependent hypertension by increasing AVP release. We speculate that normalizing the GABA equilibrium potential may have some utility in treating Na+-dependent hypertension. # Novelty and Significance {#article-title-52}Rationale: Increased arginine-vasopressin (AVP) secretion is a key physiological response to hyperosmotic stress and may be part of the mechanism by which high-salt diets induce or exacerbate hypertension. Objective: Using deoxycorticosterone acetate-salt hypertension model rats, we sought to test the hypothesis that changes in GABAA receptor–mediated inhibition in AVP-secreting magnocellular neurons contribute to the generation of Na+-dependent hypertension. Methods and Results: In vitro gramicidin-perforated recordings in the paraventricular and supraoptic nuclei revealed that the GABAergic inhibition in AVP-secreting neurons was converted into excitation in this model, because of the depolarization of GABA equilibrium potential. Meanwhile, in vivo extracellular recordings in the supraoptic nuclei showed that the GABAergic baroreflexive inhibition of magnocellular neurons was transformed to excitation, so that baroreceptor activation may increase AVP release. The depolarizing GABA equilibrium potential shift in AVP-secreting neurons occurred progressively over weeks of deoxycorticosterone acetate-salt treatment along with gradual increases in plasma AVP and blood pressure. Furthermore, the shift was associated with changes in chloride transporter expression and partially reversed by bumetanide (Na+-K+-2Cl– cotransporter inhibitor). Intracerebroventricular bumetanide administration during deoxycorticosterone acetate-salt treatment hindered the development of hypertension and rise in plasma AVP level. Muscimol (GABAA agonist) microinjection into the supraoptic nuclei in hypertensive rats increased blood pressure, which was prevented by previous intravenous V1a AVP antagonist injection. Conclusions: We conclude that the inhibitory-to-excitatory switch of GABAA receptor–mediated transmission in AVP neurons contributes to the generation of Na+-dependent hypertension by increasing AVP release. We speculate that normalizing the GABA equilibrium potential may have some utility in treating Na+-dependent hypertension.

GABAergic inhibition is weakened or converted into excitation in the oxytocin and vasopressin neurons of the lactating rat

BackgroundIncreased secretion of oxytocin and arginine vasopressin (AVP) from hypothalamic magnocellular neurosecretory cells (MNCs) is a key physiological response to lactation. In the current study, we sought to test the hypothesis that the GABAA receptor-mediated inhibition of MNCs is altered in lactating rats.ResultsGramicidin-perforated recordings in the rat supraoptic nucleus (SON) slices revealed that the reversal potential of GABAA receptor-mediated response (EGABA) of MNCs was significantly depolarized in the lactating rats as compared to virgin animals. The depolarizing EGABA shift was much larger in rats in third, than first, lactation such that GABA exerted an excitatory, instead of inhibitory, effect in most of the MNCs of these multiparous rats. Immunohistochemical analyses confirmed that GABAergic excitation was found in both AVP and oxytocin neurons within the MNC population. Pharmacological experiments indicated that the up-regulation of the Cl− importer Na+-K+-2Cl− cotransporter isotype 1 and the down-regulation of the Cl− extruder K+-Cl− cotransporter isotype 2 were responsible for the depolarizing shift of EGABA and the resultant emergence of GABAergic excitation in the MNCs of the multiparous rats.ConclusionWe conclude that, in primiparous rats, the GABAergic inhibition of MNCs is weakened during the period of lactation while, in multiparous females, GABA becomes excitatory in a majority of the cells. This reproductive experience-dependent alteration of GABAergic transmission may help to increase the secretion of oxytocin and AVP during the period of lactation.

Histamine resets the circadian clock in the suprachiasmatic nucleus through the H1R‐CaV1.3‐RyR pathway in the mouse

Histamine, a neurotransmitter/neuromodulator implicated in the control of arousal state, exerts a potent phase‐shifting effect on the circadian clock in the rodent suprachiasmatic nucleus (SCN). In this study, the mechanisms by which histamine resets the circadian clock in the mouse SCN were investigated. As a first step, Ca2+‐imaging techniques were used to demonstrate that histamine increases intracellular Ca2+ concentration ([Ca2+]i) in acutely dissociated SCN neurons and that this increase is blocked by the H1 histamine receptor (H1R) antagonist pyrilamine, the removal of extracellular Ca2+ and the L‐type Ca2+ channel blocker nimodipine. The histamine‐induced Ca2+ transient is reduced, but not blocked, by application of the ryanodine receptor (RyR) blocker dantrolene. Immunohistochemical techniques indicated that CaV1.3 L‐type Ca2+ channels are expressed mainly in the somata of SCN cells along with the H1R, whereas CaV1.2 channels are located primarily in the processes. Finally, extracellular single‐unit recordings demonstrated that the histamine‐elicited phase delay of the circadian neural activity rhythm recorded from SCN slices is blocked by pyrilamine, nimodipine and the knockout of CaV1.3 channel. Again, application of dantrolene reduced but did not block the histamine‐induced phase delays. Collectively, these results indicate that, to reset the circadian clock, histamine increases [Ca2+]i in SCN neurons by activating CaV1.3 channels through H1R, and secondarily by causing Ca2+‐induced Ca2+ release from RyR‐mediated internal stores.

Usefulness of Autologous Cartilage and Fibrin Glue for the Prevention of Septal Perforation during Septal Surgery: A Preliminary Report

Objectives: Septal surgery is one of the most common causes of nasal septal perforation. In cases in which a septal mucosal defect at the corresponding area has occurred, autologous cartilage is usually inserted between the injured mucosal flaps. In addition, we applied fibrin glue to the margins of injured mucosal surface to fix the inserted cartilage and to promote mucosal regeneration. The aim of this study was to evaluate the efficacy of this method in the prevention of nasal septal perforation.

Transanal gauze packing to manage massive presacral bleeding secondary to prescral abscess caused by rectal anastomotic leakage: A novel approach

Anastomotic leakage following rectal resection is a serious and fearful complication, and may cause presacral abscess and/or peritonitis. To our knowledge, massive hematochezia secondary to presacral abscess caused by anastomotic leakage has not yet been reported in the literature. We observed this rare and life-threatening complication in three patients who were successfully treated with a simple but effective transanal gauze packing technique.

GABAergic Excitation of Vasopressin Neurons

Rationale: Increased arginine-vasopressin (AVP) secretion is a key physiological response to hyperosmotic stress and may be part of the mechanism by which high-salt diets induce or exacerbate hypertension. Objective: Using deoxycorticosterone acetate-salt hypertension model rats, we sought to test the hypothesis that changes in GABAA receptor–mediated inhibition in AVP-secreting magnocellular neurons contribute to the generation of Na+-dependent hypertension. Methods and Results: In vitro gramicidin-perforated recordings in the paraventricular and supraoptic nuclei revealed that the GABAergic inhibition in AVP-secreting neurons was converted into excitation in this model, because of the depolarization of GABA equilibrium potential. Meanwhile, in vivo extracellular recordings in the supraoptic nuclei showed that the GABAergic baroreflexive inhibition of magnocellular neurons was transformed to excitation, so that baroreceptor activation may increase AVP release. The depolarizing GABA equilibrium potential shift in AVP-secreting neurons occurred progressively over weeks of deoxycorticosterone acetate-salt treatment along with gradual increases in plasma AVP and blood pressure. Furthermore, the shift was associated with changes in chloride transporter expression and partially reversed by bumetanide (Na+-K+-2Cl– cotransporter inhibitor). Intracerebroventricular bumetanide administration during deoxycorticosterone acetate-salt treatment hindered the development of hypertension and rise in plasma AVP level. Muscimol (GABAA agonist) microinjection into the supraoptic nuclei in hypertensive rats increased blood pressure, which was prevented by previous intravenous V1a AVP antagonist injection. Conclusions: We conclude that the inhibitory-to-excitatory switch of GABAA receptor–mediated transmission in AVP neurons contributes to the generation of Na+-dependent hypertension by increasing AVP release. We speculate that normalizing the GABA equilibrium potential may have some utility in treating Na+-dependent hypertension. # Novelty and Significance {#article-title-52}Rationale: Increased arginine-vasopressin (AVP) secretion is a key physiological response to hyperosmotic stress and may be part of the mechanism by which high-salt diets induce or exacerbate hypertension. Objective: Using deoxycorticosterone acetate-salt hypertension model rats, we sought to test the hypothesis that changes in GABAA receptor–mediated inhibition in AVP-secreting magnocellular neurons contribute to the generation of Na+-dependent hypertension. Methods and Results: In vitro gramicidin-perforated recordings in the paraventricular and supraoptic nuclei revealed that the GABAergic inhibition in AVP-secreting neurons was converted into excitation in this model, because of the depolarization of GABA equilibrium potential. Meanwhile, in vivo extracellular recordings in the supraoptic nuclei showed that the GABAergic baroreflexive inhibition of magnocellular neurons was transformed to excitation, so that baroreceptor activation may increase AVP release. The depolarizing GABA equilibrium potential shift in AVP-secreting neurons occurred progressively over weeks of deoxycorticosterone acetate-salt treatment along with gradual increases in plasma AVP and blood pressure. Furthermore, the shift was associated with changes in chloride transporter expression and partially reversed by bumetanide (Na+-K+-2Cl– cotransporter inhibitor). Intracerebroventricular bumetanide administration during deoxycorticosterone acetate-salt treatment hindered the development of hypertension and rise in plasma AVP level. Muscimol (GABAA agonist) microinjection into the supraoptic nuclei in hypertensive rats increased blood pressure, which was prevented by previous intravenous V1a AVP antagonist injection. Conclusions: We conclude that the inhibitory-to-excitatory switch of GABAA receptor–mediated transmission in AVP neurons contributes to the generation of Na+-dependent hypertension by increasing AVP release. We speculate that normalizing the GABA equilibrium potential may have some utility in treating Na+-dependent hypertension.

GABAergic Excitation of Vasopressin NeuronsNovelty and Significance

Rationale: Increased arginine-vasopressin (AVP) secretion is a key physiological response to hyperosmotic stress and may be part of the mechanism by which high-salt diets induce or exacerbate hypertension. Objective: Using deoxycorticosterone acetate-salt hypertension model rats, we sought to test the hypothesis that changes in GABAA receptor–mediated inhibition in AVP-secreting magnocellular neurons contribute to the generation of Na+-dependent hypertension. Methods and Results: In vitro gramicidin-perforated recordings in the paraventricular and supraoptic nuclei revealed that the GABAergic inhibition in AVP-secreting neurons was converted into excitation in this model, because of the depolarization of GABA equilibrium potential. Meanwhile, in vivo extracellular recordings in the supraoptic nuclei showed that the GABAergic baroreflexive inhibition of magnocellular neurons was transformed to excitation, so that baroreceptor activation may increase AVP release. The depolarizing GABA equilibrium potential shift in AVP-secreting neurons occurred progressively over weeks of deoxycorticosterone acetate-salt treatment along with gradual increases in plasma AVP and blood pressure. Furthermore, the shift was associated with changes in chloride transporter expression and partially reversed by bumetanide (Na+-K+-2Cl– cotransporter inhibitor). Intracerebroventricular bumetanide administration during deoxycorticosterone acetate-salt treatment hindered the development of hypertension and rise in plasma AVP level. Muscimol (GABAA agonist) microinjection into the supraoptic nuclei in hypertensive rats increased blood pressure, which was prevented by previous intravenous V1a AVP antagonist injection. Conclusions: We conclude that the inhibitory-to-excitatory switch of GABAA receptor–mediated transmission in AVP neurons contributes to the generation of Na+-dependent hypertension by increasing AVP release. We speculate that normalizing the GABA equilibrium potential may have some utility in treating Na+-dependent hypertension. # Novelty and Significance {#article-title-52}Rationale: Increased arginine-vasopressin (AVP) secretion is a key physiological response to hyperosmotic stress and may be part of the mechanism by which high-salt diets induce or exacerbate hypertension. Objective: Using deoxycorticosterone acetate-salt hypertension model rats, we sought to test the hypothesis that changes in GABAA receptor–mediated inhibition in AVP-secreting magnocellular neurons contribute to the generation of Na+-dependent hypertension. Methods and Results: In vitro gramicidin-perforated recordings in the paraventricular and supraoptic nuclei revealed that the GABAergic inhibition in AVP-secreting neurons was converted into excitation in this model, because of the depolarization of GABA equilibrium potential. Meanwhile, in vivo extracellular recordings in the supraoptic nuclei showed that the GABAergic baroreflexive inhibition of magnocellular neurons was transformed to excitation, so that baroreceptor activation may increase AVP release. The depolarizing GABA equilibrium potential shift in AVP-secreting neurons occurred progressively over weeks of deoxycorticosterone acetate-salt treatment along with gradual increases in plasma AVP and blood pressure. Furthermore, the shift was associated with changes in chloride transporter expression and partially reversed by bumetanide (Na+-K+-2Cl– cotransporter inhibitor). Intracerebroventricular bumetanide administration during deoxycorticosterone acetate-salt treatment hindered the development of hypertension and rise in plasma AVP level. Muscimol (GABAA agonist) microinjection into the supraoptic nuclei in hypertensive rats increased blood pressure, which was prevented by previous intravenous V1a AVP antagonist injection. Conclusions: We conclude that the inhibitory-to-excitatory switch of GABAA receptor–mediated transmission in AVP neurons contributes to the generation of Na+-dependent hypertension by increasing AVP release. We speculate that normalizing the GABA equilibrium potential may have some utility in treating Na+-dependent hypertension.

GABAergic Excitation of Vasopressin NeuronsNovelty and Significance: Possible Mechanism Underlying Sodium-Dependent Hypertension

Rationale: Increased arginine-vasopressin (AVP) secretion is a key physiological response to hyperosmotic stress and may be part of the mechanism by which high-salt diets induce or exacerbate hypertension. Objective: Using deoxycorticosterone acetate-salt hypertension model rats, we sought to test the hypothesis that changes in GABAA receptor–mediated inhibition in AVP-secreting magnocellular neurons contribute to the generation of Na+-dependent hypertension. Methods and Results: In vitro gramicidin-perforated recordings in the paraventricular and supraoptic nuclei revealed that the GABAergic inhibition in AVP-secreting neurons was converted into excitation in this model, because of the depolarization of GABA equilibrium potential. Meanwhile, in vivo extracellular recordings in the supraoptic nuclei showed that the GABAergic baroreflexive inhibition of magnocellular neurons was transformed to excitation, so that baroreceptor activation may increase AVP release. The depolarizing GABA equilibrium potential shift in AVP-secreting neurons occurred progressively over weeks of deoxycorticosterone acetate-salt treatment along with gradual increases in plasma AVP and blood pressure. Furthermore, the shift was associated with changes in chloride transporter expression and partially reversed by bumetanide (Na+-K+-2Cl– cotransporter inhibitor). Intracerebroventricular bumetanide administration during deoxycorticosterone acetate-salt treatment hindered the development of hypertension and rise in plasma AVP level. Muscimol (GABAA agonist) microinjection into the supraoptic nuclei in hypertensive rats increased blood pressure, which was prevented by previous intravenous V1a AVP antagonist injection. Conclusions: We conclude that the inhibitory-to-excitatory switch of GABAA receptor–mediated transmission in AVP neurons contributes to the generation of Na+-dependent hypertension by increasing AVP release. We speculate that normalizing the GABA equilibrium potential may have some utility in treating Na+-dependent hypertension. # Novelty and Significance {#article-title-52}Rationale: Increased arginine-vasopressin (AVP) secretion is a key physiological response to hyperosmotic stress and may be part of the mechanism by which high-salt diets induce or exacerbate hypertension. Objective: Using deoxycorticosterone acetate-salt hypertension model rats, we sought to test the hypothesis that changes in GABAA receptor–mediated inhibition in AVP-secreting magnocellular neurons contribute to the generation of Na+-dependent hypertension. Methods and Results: In vitro gramicidin-perforated recordings in the paraventricular and supraoptic nuclei revealed that the GABAergic inhibition in AVP-secreting neurons was converted into excitation in this model, because of the depolarization of GABA equilibrium potential. Meanwhile, in vivo extracellular recordings in the supraoptic nuclei showed that the GABAergic baroreflexive inhibition of magnocellular neurons was transformed to excitation, so that baroreceptor activation may increase AVP release. The depolarizing GABA equilibrium potential shift in AVP-secreting neurons occurred progressively over weeks of deoxycorticosterone acetate-salt treatment along with gradual increases in plasma AVP and blood pressure. Furthermore, the shift was associated with changes in chloride transporter expression and partially reversed by bumetanide (Na+-K+-2Cl– cotransporter inhibitor). Intracerebroventricular bumetanide administration during deoxycorticosterone acetate-salt treatment hindered the development of hypertension and rise in plasma AVP level. Muscimol (GABAA agonist) microinjection into the supraoptic nuclei in hypertensive rats increased blood pressure, which was prevented by previous intravenous V1a AVP antagonist injection. Conclusions: We conclude that the inhibitory-to-excitatory switch of GABAA receptor–mediated transmission in AVP neurons contributes to the generation of Na+-dependent hypertension by increasing AVP release. We speculate that normalizing the GABA equilibrium potential may have some utility in treating Na+-dependent hypertension.