Oral sodium oxybate does not alter plasma kisspeptin levels in healthy male volunteers.

Gamma-hydroxybutyrate (GHB, clinically administrated as sodium oxybate) is a GABA-B/GHB receptor agonist inducing prosexual effects and progesterone secretion in humans. As the neuropeptide kisspeptin has well-established roles in regulating sexual behavior and as it was also associated with GABA-B receptor and progesterone function, we investigated the effect of two GHB doses (20 and 35 mg/kg p.o.) on plasma kisspeptin levels in 30 healthy male volunteers, using a double-blind, randomized, placebo-controlled cross-over design. We found no significant alterations of kisspeptin levels after GHB administration compared to placebo. In conclusion, plasma kisspeptin levels are not related to the prosexual effects of GHB.

Subacute changes in brain functional network connectivity after nocturnal sodium oxybate intake are associated with anterior cingulate GABA.

Sodium oxybate (γ-hydroxybutyrate, GHB) is an endogenous GHB/GABAB receptor agonist, clinically used to promote slow-wave sleep and reduce next-day sleepiness in disorders such as narcolepsy and fibromyalgia. The neurobiological signature of these unique therapeutic effects remains elusive. Promising current neuropsychopharmacological approaches to understand the neural underpinnings of specific drug effects address cerebral resting-state functional connectivity (rsFC) patterns and neurometabolic alterations. Hence, we performed a placebo-controlled, double-blind, randomized, cross-over pharmacological magnetic resonance imaging study with a nocturnal administration of GHB, combined with magnetic resonance spectroscopy of GABA and glutamate in the anterior cingulate cortex (ACC). In sum, 16 healthy male volunteers received 50 mg/kg GHB p.o. or placebo at 02:30 a.m. to maximize deep sleep enhancement and multi-modal brain imaging was performed at 09:00 a.m. of the following morning. Independent component analysis of whole-brain rsFC revealed a significant increase of rsFC between the salience network (SN) and the right central executive network (rCEN) after GHB intake compared with placebo. This SN-rCEN coupling was significantly associated with changes in GABA levels in the ACC (pall < 0.05). The observed neural pattern is compatible with a functional switch to a more extrinsic brain state, which may serve as a neurobiological signature of the wake-promoting effects of GHB.

Comorbidity of ketamine dependence with major depressive disorder increases the vulnerability to neuroaxonal pathology.

We recently demonstrated that patients with ketamine dependence (KD) have increased serum levels of neurofilament light chain (NfL), a novel marker of active neuroaxonal pathology, with NfL levels being significantly higher in those KD patients comorbid with major depressive disorder (MDD). However, considering that NfL elevation has been associated with both ketamine-related brain pathology and MDD, we could not determine whether the observed elevation of NfL levels was driven by an interaction of KD with MDD or by MDD itself. Therefore, we compared serum NfL levels between 35 patients with MDD without ketamine use (MDD group), 23 with KD without MDD (KD without MDD group), 30 KD with MDD (KD with MDD group), and 86 healthy controls (HC group). Using a 2*2 (KD*MDD) generalized linear model controlling for age, sex, body mass index, and smoking status, we found that KD and KD*MDD interactions, but not MDD factor, significantly affected NfL levels. Posthoc tests showed that the KD with MDD group had significantly higher NfL levels than all other groups. The KD without MDD group also showed higher NfL levels than the MDD and, as shown before, HC groups. The levels in MDD group were not different from the HC group. These results suggest that the interaction of KD with MDD, but not MDD alone, results in increased vulnerability to neuroaxonal pathology.