Naloxone (hydrochloride) is an opioid receptor antagonist [1].

Opioid receptors include 3 subtypes, namely, μ-, δ-, and κ-opioid receptors, which can be activated by various endogenous peptides, and also drugs of abuse such as morphine and heroin. Activation of opioid receptors leads to the regulation of many biological functions including pain perception, motivation, locomotion, hormone secretion, and reward [2].

In neural stem cells (NSCs), naloxone facilitated the proliferation of NSCs in a concentration-dependent manner. Naloxone at 1 μM increased the final number of NSCs to an even higher level than morphine at 1 μM, approximately 150% of the basal level [1]. In human peripheral blood mononuclear cells, naloxone triggered a significant reduction of natural killer cell activity only at very high concentrations, 1 × 10^-3 M and above [3].

Naloxone (0.625, 2.5 or 10 mg/kg, i.p.) caused a dose-dependent reduction of break-points and locomotor activity in both the beer and near-beer rats. However, the effects of naloxone on breakpoints were significantly more pronounced on rats drinking beer compared to those drinking near-beer [4].

References:

[1]. Liang L, Chen J, Li Y, et al. Morphine and naloxone facilitate neural stem cells proliferation via a TET1-dependent and receptor-independent pathway. Cell Reports, 2020, 30(11): 3625-3631.

[2]. Gomes I, Fujita W, Chandrakala M V, et al. Chapter Nine - Disease-specific heteromerization of G-protein-coupled receptors that target drugs of abuse. Progress in Molecular Biology and Translational Science, 2013, 117: 207-265.

[3]. Adelson M O, Novick D M, Khuri E, et al. Effects of the opioid antagonist naloxone on human natural killer cell activity in vitro. Israel Journal of Medical Sciences, 1994, 30(9): 679-684.

[4]. Gallate J E, McGregor I S. The motivation for beer in rats: effects of ritanserin, naloxone and SR 141716. Psychopharmacology (Berl), 1999, 142(3): 302-308.