Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2011 Jun 9;54(11):3926-34.
doi: 10.1021/jm2002487. Epub 2011 May 6.

Neurosteroid Analogues. 16. A New Explanation for the Lack of Anesthetic Effects of δ(16)-alphaxalone and Identification of a δ(17(20)) Analogue With Potent Anesthetic Activity

Affiliations
Free PMC article

Neurosteroid Analogues. 16. A New Explanation for the Lack of Anesthetic Effects of δ(16)-alphaxalone and Identification of a δ(17(20)) Analogue With Potent Anesthetic Activity

Eva Stastna et al. J Med Chem. .
Free PMC article

Abstract

This study addresses the hypothesis that the lack of anesthetic activity for (3α,5α)-3-hydroxypregn-16-ene-11,20-dione (Δ(16)-alphaxalone) is explained by the steroid Δ(16) double bond constraining the steroid 20-carbonyl group to a position that prevents it from favorably interacting with γ-aminobutyric acid type A (GABA(A)) receptors. A series of Δ(16) and Δ(17(20)) analogues of Δ(16)-alphaxalone was prepared to evaluate this hypothesis in binding, electrophysiological, and tadpole anesthesia experiments. The results obtained failed to support the hypothesis. Instead, the results indicate that it is the presence of the C-21 methyl group in Δ(16)-alphaxalone, not the location of the constrained C-20 carbonyl group, that prevents Δ(16)-alphaxalone from interacting strongly with the GABA(A) receptor and having anesthetic activity. Consistent with this conclusion, a Δ(17(20)) analogue of Δ(16)-alphaxalone without a C-21 methyl group was found to be very similar to the anesthetic steroid (3α,5α)-3-hydroxypregnane-11,20-dione (alphaxalone) with regard to time of onset and rate of recovery from anesthesia when administered to mice by tail vein injection.

Figures

Figure 1
Figure 1
Projection plot (50% thermal ellipsoids) of the X-ray crystal structure of steroid 6a.
Figure 2
Figure 2
Molecular models showing steroids 5a (top) and 6a (middle) and their overlay (bottom). Left column, edge view. Right column, top view.
Figure 3
Figure 3
Direct quantitative comparison of steroids 6a, 6b and 5c at 10 µM on responses to GABA in Xenopus oocytes expressing α1β2γ2L GABAA receptor subunits. A. Responses of to 2 µM GABA alone (left trace) and to GABA co-applied with 10 µM each of 6a (second trace), 6b (third trace) and 5c (right trace). All responses are from the same oocyte. B. Summary of responses in which 6a, 6b and 5c were tested within oocytes, normalized to the response of GABA alone in each oocyte. The normalizing response is indicated with a dotted horizontal line at y = 1 (N = 4). Error bars are SEM.
Figure 4
Figure 4
Summary of normalized responses of oocytes to co-applied GABA (2 µM) plus 1 µM (left set of bars) or 10 µM (right set of bars) of the indicated compounds, tested within oocytes. The normalizing response of GABA alone is indicated by the horizontal dotted line at y = 1. Bars represent mean responses of 6 to 7 oocytes for each compound. Error bars are SEM.
Figure 5
Figure 5
A rank order correlation plot of the analogue [35S]-TBPS IC50 values with their corresponding tadpole LRR EC50 values. Compound numbers are used to represent data points on the plot. The correlation is significant, r = 0.8, (p < 0.05).
Figure 6
Figure 6
Duration of anesthesia induced by tail vein injection of steroids 1 and 6a into mice at two doses. The steroids were dissolved in 22.5% aqueous 2-(hydroxypropyl)-β-cyclodextrin. Numbers of animals tested are given above the bars.
Scheme 1<i>a</i>
Scheme 1a
aReagents: a) MOMCl, Hunig’s base, CH2Cl2; b) PhN(SO2CF3)2, KHMDS, THF, –78 °C; c) NaCN, CuI, Pd(PPh3)4, MeCN; d) DIBALH, toluene, CH2Cl2, –78 °C; e) PCC, CH2Cl2, f) EtOH, 6 N HCl; g) H2 (60 psi), Lindlar’s catalyst (5%), EtOAc.
Scheme 2<i>a</i>
Scheme 2a
aReagents: a) NaH, diethyl(cyanomethyl)phosphonate, THF, 0 to 20 °C; b) H2 (60 psi), Pd/C, EtOAc/EtOH.
Scheme 3
Scheme 3
aReagents: a) Ac2O, pyridine; b) KCN, pyridine, AcOH, EtOH, 0 to 20 °C; c) POCl3 pyridine; d) K2CO3, MeOH, reflux.
Chart 1
Chart 1
Chart 2
Chart 2

Similar articles

See all similar articles

Cited by 3 articles

Publication types

MeSH terms

LinkOut - more resources

Feedback