Article

Effects of sazetidine-A, a selective α4β2* nicotinic receptor desensitizing agent, on body temperature regulation in mice and rats

Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC 27710, USA.
European journal of pharmacology (Impact Factor: 2.53). 02/2012; 682(1-3):110-7. DOI: 10.1016/j.ejphar.2012.02.031
Source: PubMed

ABSTRACT

Nicotine-induced hypothermia is well established, but the nicotinic receptor actions underlying this effect are not clear. Nicotine causes activation and desensitization at a variety of nicotinic receptor subtypes. Sazetidine-A [6-(5(((S)-azetidine-2-yl)methoxy)pyridine-3-yl)hex-5-yn-1-ol] is a novel compound that potently and selectively desensitizes α4β2* nicotinic receptors. The main goal of this study was to investigate the effects of sazetidine-A, on core body temperature (Tc) in mice and rats. Sazetidine-A effects on Tc and the interactions of sazetidine-A with nicotine and selective nicotinic antagonists were investigated to determine the receptor actions underlying nicotine-induced hypothermia. Adult male mice were injected with different dose of nicotine (0.2, 0.4 and 0.8 mg/kg), sazetidine-A (0.3, 1, and 3mg/kg), a mixture of nicotine (0.4 or 0.8 mg/kg) and sazetidine-A (0.3 or 0.6 mg/kg) or saline and Tc was monitored telemetrically. In another set of experiments, the interaction between sazetidine-A and dihydro-β-erythroidine (DHβE), an α4β2* nicotinic receptors antagonist, and methyllycaconitine (MLA), an α7 antagonist, was investigated. Tc of mice was monitored following DHβE (1, 3 and 6 mg/kg), a combination of DHβE (3mg/kg) and sazetidine-A (0.6 mg/kg), MLA (1.5, 3 or 6 mg/kg) or combination of MLA (6 mg/kg) and sazetidine (0.6 mg/kg) or saline. The acute effect of sazetidine-A (1, 3, and 6 mg/kg) on rats Tc was also studied. Acute sazetidine-A caused a pronounced and long-lasting hypothermia in mice; Tc decreased to about 28°C at 100 min and recovered within 230 min. The hypothermic effect of sazetidine in rats was much less in magnitude (about 3°C) and shorter in duration compared with that in mice. Nicotine co-administration with low doses of sazetidine potentiated the magnitude and duration of hypothermia in mice. The α4β2* nicotinic receptors antagonist DHβE significantly prolonged sazetidine-A-induced hypothermia but did not increase its depth. The α7 antagonist MLA caused a modest degree of hypothermia with relatively short duration in mice. MLA failed to counteract the sazetidine-A-induced hypothermia. Overall, our results show that pharmacological modulation of α4β2* nicotinic receptors elicits changes in body temperature that may involve desensitization of these receptors.

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    • "Additionally, the observation that both a nAChR antagonist and agonists reduce LIDs suggested that nAChR drugs decrease LIDs via a receptor desensitization blockade. This idea is consistent with other studies indicating that nicotine exerts its antidepressant, cognition, and other effects via nAChR desensitization (Buccafusco, Beach, & Terry, 2009;Mineur & Picciotto, 2010;Rezvani et al., 2012). Overall, these data confirm that the antidyskinetic effect of nicotine is nAChR mediated and led the way for further pharmacological studies with subtype-selective nAChR drugs. "
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    • "The mechanism through which the α4β2 nAChR antagonist confers neuroprotection in awake mice remains speculative but it was not a consequence of increased collateral blood flow or changes in physiological variables such as heart rate, respiration, blood gas or electrolyte concentrations. Furthermore, a recent study demonstrated that systemic injection of DHβE (at 3 mg/kg) in adult C57BL6 mice has minimal effect on core body temperature, thus ruling out hypothermia as a cause (Rezvani et al., 2012). While beyond the scope of the present study, future experiments directed at understanding how α4β2 nAChRs modulate glutamate release/excitotoxicity (Lambe et al., 2003), spreading depression (Sheardown, 1997; Douglas et al., 2011), blood brain barrier permeability (Hawkins et al., 2005) or inflammatory responses to ischemia should help resolve this issue. "
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    • "Additionally, the observation that both a nAChR antagonist and agonists reduce LIDs suggested that nAChR drugs decrease LIDs via a receptor desensitization blockade. This idea is consistent with other studies indicating that nicotine exerts its antidepressant, cognition, and other effects via nAChR desensitization (Buccafusco, Beach, & Terry, 2009;Mineur & Picciotto, 2010;Rezvani et al., 2012). Overall, these data confirm that the antidyskinetic effect of nicotine is nAChR mediated and led the way for further pharmacological studies with subtype-selective nAChR drugs. "
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