27 research outputs found
Identification of Novel α4β2-Nicotinic Acetylcholine Receptor (nAChR) Agonists Based on an Isoxazole Ether Scaffold that Demonstrate Antidepressant-like Activity
There is considerable evidence to support the hypothesis
that the
blockade of nAChR is responsible for the antidepressant action of
nicotinic ligands. The nicotinic acetylcholine receptor (nAChR) antagonist,
mecamylamine, has been shown to be an effective add-on in patients
that do not respond to selective serotonin reuptake inhibitors. This
suggests that nAChR ligands may address an unmet clinical need by
providing relief from depressive symptoms in refractory patients.
In this study, a new series of nAChR ligands based on an isoxazole-ether
scaffold have been designed and synthesized for binding and functional
assays. Preliminary structure–activity relationship (SAR) efforts
identified a lead compound <b>43</b>, which possesses potent
antidepressant-like activity (1 mg/kg, IP; 5 mg/kg, PO) in the classical
mouse forced swim test. Early stage absorption, distribution, metabolism,
excretion, and toxicity (ADME-Tox) studies also suggested favorable
drug-like properties, and broad screening toward other common neurotransmitter
receptors indicated that compound <b>43</b> is highly selective
for nAChRs over the other 45 neurotransmitter receptors and transporters
tested
Chemistry, Pharmacology, and Behavioral Studies Identify Chiral Cyclopropanes as Selective α4β2-Nicotinic Acetylcholine Receptor Partial Agonists Exhibiting an Antidepressant Profile. Part II
A 3-pyridyl
ether scaffold bearing a cyclopropane-containing side
chain was recently identified in our efforts to create novel antidepressants
that act as partial agonists at α4β2-nicotinic acetylcholine
receptors. In this study, a systematic structure–activity relationship
investigation was carried out on both the azetidine moiety present
in compound <b>3</b> and its right-hand side chain, thereby
discovering a variety of novel nicotinic ligands that retain bioactivity
and feature improved chemical stability. The most promising compounds, <b>24</b>, <b>26</b>, and <b>30</b>, demonstrated comparable
or enhanced pharmacological profiles compared to the parent compound <b>4</b>, and the <i>N</i>-methylpyrrolidine analogue <b>26</b> also exhibited robust antidepressant-like efficacy in the
mouse forced swim test. The favorable ADMET profile and chemical stability
of <b>26</b> further indicate this compound to be a promising
lead as a drug candidate warranting further advancement down the drug
discovery pipeline
Excitatory synaptic function is selectively enhanced in CA1 of hippocampal brain slices following <i>in vitro</i> SAHA treatment.
<p>(A) The median amplitude of mEPSCs was significantly increased in SAHA-treated slices (p<0.05, n = 14 vehicle, 14 SAHA), while there was no significant change to mEPSC frequency as measured by the median interval between events (p>0.05). Example mEPSC traces from vehicle and SAHA treated slices are shown inset (scale bar represents 10 pA and 250 ms). (B) SAHA treatment did not significantly alter the amplitude or frequency of mIPSCs (p>0.05, n = 14, 11). Example mIPSC traces from vehicle and SAHA treated slices are shown inset (scale bar represents 10 pA and 500 ms). All data points are plotted as mean ±SEM.</p
SAHA IC<sub>50</sub> values for each HDAC isozyme are shown as measured using <i>in vitro</i> enzymatic assays.
<p>Values are in µM and confidence intervals are in parentheses.</p
SAHA treated slices exhibit enhanced induction of LTP and impaired LTD.
<p>(A) An induction protocol that was subthreshold in vehicle treated slices readily evoked LTP in SAHA treated slices (p<0.05, n = 5,5). Example traces before and after LTP induction are shown in red for SAHA and black for vehicle treated slices (scale bars represent 20 pA and 20 ms). (B) An induction protocol that readily induced LTD in vehicle treated slices could not produce LTD in SAHA treated slices (p<0.05, n = 9 vehicle, 8 SAHA). Example traces before and after LTD induction are shown in red for SAHA and black for vehicle treated slices (scale bars represent 25 pA and 20 ms). Data are plotted as mean ±SEM.</p
Pharmacokinetic analysis of SAHA following i.p. injection.
<p>A) Bioanalysis of the time course of total (top) and unbound (bottom) plasma, CSF, and brain levels of SAHA following a single 50 mg/kg ip injection (n = 3 mice/time point). The dotted red lines represent the SAHA concentration imposed on the <i>in vitro</i> slice cultures for the electrophysiological studies. B) Total (top) and unbound (bottom) SAHA levels are shown following a 150 mg/kg ip injection (n = 3/time point). All data is shown as mean ± SD.</p
Fear memory deficits in Tg2576 mice are not rescued by SAHA treatment.
<p>A) Compared to non-transgenic littermates (n = 15), Tg2576 (n = 14) mice showed significantly less freezing than wt mice when returned to the context in which conditioning occurred (context, p<0.001), when placed in an altered context (altered, p<0.01), or in response to the cue used for conditioning (cue, p<0.05). B) Tg2576 mice were treated daily for 33 days prior to, as well as during fear conditioning with either vehicle (n = 14), 25 mg/kg SAHA (n = 13), or 50 mg/kg SAHA (n = 13). There was no effect of treatment on the percentage of time Tg2576 mice spent freezing in response to the context, altered context, or cue (p>0.05). C) There was no effect of treatment on the percentage of time spent freezing during conditioning (p>0.05). D) There was no effect of treatment on the distance traveled in the open field test (total distance = 38.0±7.7 m for vehicle, 39.6±6.1 m for 25 mg/kg SAHA, and 34.2±5.2 m for 50 mg/kg SAHA, p>0.05). All data are plotted as mean ±SEM.</p
Acute or chronic SAHA treatment does not produce significant drug class activity signatures as assessed by the SmartCube®.
<p>A. Groups of mice were treated acutely with a single injection of 50 mg/kg or 150 mg/kg SAHA or vehicle. In addition, a group was treated with valproate (225 mg/kg). Both does of SAHA were behaviorally inactive without a clear therapeutic signal. In contrast valproate was behaviorally active (p<0.001, discrimination index = 100%) with a strong anxiolytic signature and a mild psychostimulant signature. B. Groups of mice were treated daily for 14 days with SAHA or Valproate. While the lower dose of SAHA appeared behaviorally active (p<0.001, discrimination index = 88%), the activity was not consistent with any known therapeutic signal and the higher dose was not behaviorally active. In contrast valproate showed a strong behavioral activity (p<0.001, discrimination index = 98%) with a predominantly anxiolytic signature. C. The legend shows the 15 classes of behavioral activity that were assessed.</p
Intrinsic membrane properties are unaltered by SAHA treatment.
<p>(A) Representative traces from vehicle (black) and SAHA (red) treated slices during a series of hyperpolarizing and depolarizing current injection steps (scale bar represents 20 mV and 100 ms). There was no difference between vehicle and SAHA treated slices in the number of action potentials elicited by 500 ms current injection pulses at any of the current injection levels (p>0.05, n = 7,7). (B) Action potential threshold, input resistance, and membrane sag reflecting the hyperpolarization-induced inward current, were all unaltered following SAHA treatment (p>0.05). Data are plotted as mean ±SEM.</p
NeuroCube Results at P30 and P60.
<p>Analysis of NeuroCube data showed that the 16p11.2 df/+ mice were significantly different from the WT control mice overall, and, in particular, for paw imaging and position features. Gait was different only at P60. The Cntnap2 -/- mice were also different overall and, in particular, in their speed and gait features. The numbers shown are the maximal discrimination found between the two groups.</p><p>*Indicates that the associated <i>p</i>-value was less than .05.</p><p>NeuroCube Results at P30 and P60.</p