ABSTRACT
ß(3)-adrenoceptor is a potential target for uterine relaxant drugs for the treatment of preterm labor. Mouse is an ideal experimental model for preterm labor. However, there is limited information on the molecular and functional characteristics of ß(3)-adrenoceptors in mouse uterus. Therefore, the current study was undertaken to characterize the ß(3)-adrenoceptors in late pregnant mouse uterus by molecular and functional experiments and to compare their expression and function with the ß(2)-adrenoceptors. Using RT-PCR, we demonstrated the presence of ß(3)-adrenoceptor mRNA in the mouse uterus. Accordingly, selective ß(3)-adrenoceptor agonist SAR150640 (ethyl-4-{trans-4-[((2S)-2-hydroxy-3-{4-hydroxy-3[(methylsulfonyl)amino]-phenoxy}propyl)amino]cyclohexyl}benzoate hydrochloride) caused concentration-dependent relaxation of the isolated tissue. SR59230A (1 µM), a selective antagonist of ß(3)-adrenoceptors, antagonized the relaxant response to SAR150640. Using real-time PCR we found that in comparison to ß(3)-adrenoceptor mRNA, ß(2)-adrenoceptor mRNA is predominantly expressed in the late pregnant mouse uterus. We then assessed the comparative efficiency of different ß-adrenoceptor agonists, such as SAR150640, salbutamol and isoprenaline to relax the tissue. SAR150640 (pD(2) 6.64±0.21, E(max) 104.9±7.95), salbutamol (pD(2) 8.57±0.062, E(max) 103.1±3.22) and isoprenaline (pD(2) 9.48±0.084, E(max) 102.9±5.18) caused concentration-dependent inhibition of uterine rhythmic contractions. While the maximal relaxation to these agonists was comparable, the order of potency was isoprenaline>salbutamol>SAR. These results suggest that ß(3)-adrenoceptor mRNA is present in the pregnant mouse uterus and is functionally active. The predominance of ß(2)- over ß(3)-adrenoceptor expression may explain variable potency amongst the ß-adrenoceptor agonists.
Subject(s)
Receptors, Adrenergic, beta-2/metabolism , Receptors, Adrenergic, beta-3/metabolism , Uterus/metabolism , Adrenergic beta-2 Receptor Agonists/pharmacology , Adrenergic beta-3 Receptor Agonists/pharmacology , Adrenergic beta-3 Receptor Antagonists/pharmacology , Albuterol/pharmacology , Animals , Benzoates/pharmacology , Female , Gene Expression Regulation/drug effects , In Vitro Techniques , Isoproterenol/pharmacology , Male , Pregnancy , Propanolamines/pharmacology , Receptors, Adrenergic, beta-2/genetics , Receptors, Adrenergic, beta-3/genetics , Sulfonamides/pharmacology , Uterine Contraction/drug effects , Uterus/drug effects , Uterus/physiologyABSTRACT
Chloride channels belong to diverse group of anion selective channels involved in different signaling processes. The present study was planned to investigate the involvement of chloride channels in crush injury-induced neuropathic pain in rats by using ivermectin, a ligand gated chloride channel opener and NPPB, a CaCC blocker. The effect of ivermectin (5, 10, 20 mg/kg i.p. or 50, 100 and 200 microg/rat by i.c.v. route) and NPPB (10, 20 and 40 mg/kg i.p.) was investigated on pain behavioural thresholds in crush injury-induced neuropathic pain rat model. Reduction in pain threshold by mechanical, thermal and cold stimuli confirmed the development of neuropathic pain in rats after crush injury. Ivermectin administered either by i.p. or i.c.v. route did not alter the pain threshold in mechanical, thermal and, cold allodynia tests in rats. NPPB (20 and 40 mg/kg i.p.) significantly reduced the pain threshold crush injury neuropathic pain model suggesting its hyperalgesic effect. The results showed that NPPB increased significantly the mechanical and thermal hyperalgesia in crush injury-induced neuropathic pain rat model, whereas ivermectin, either by i.p. or i.c.v. route of administration, has no effect on pain symptoms in this model. NPPB hyperalgesic effect is independent of CaCCs inhibition and may be due to blockade of Ca2+-activated K+ channel.
Subject(s)
Angiogenesis Inhibitors , Chloride Channels/antagonists & inhibitors , Hyperalgesia/chemically induced , Hyperalgesia/psychology , Nerve Crush , Nitrobenzoates , Pain/psychology , Peripheral Nervous System Diseases/psychology , Animals , Behavior, Animal/drug effects , Cold Temperature , Hot Temperature , Hyperalgesia/pathology , Injections, Intraventricular , Ivermectin/pharmacology , Ligands , Male , Pain/pathology , Pain Threshold/drug effects , Peripheral Nervous System Diseases/pathology , Physical Stimulation , Rats , Rats, WistarABSTRACT
In the present investigation we have examined the hypothesis that calcium-dependent K+ channels (K(Ca)) are involved in the sodium nitroprusside (SNP)-induced vasodilatation of goat coronary artery. SNP (10(-9)-3 x 10(-6) M), added cumulatively, relaxed K+ (30 mM)-contracted coronary artery ring segments in a concentration-dependent manner with an EC50 of 1.32 x 10(-7) M (95% CL, 0.93-1.86 x 10(-7) M; n = 21). K(Ca) blocker, tetraethyl ammonium (1 mM) caused a rightward shift in the concentration-response curve of SNP with a corresponding increase in EC50 (1.62 x 10(-6) M; 95% CL, 0.44-6.02 x 10(-6) M, n = 4) of nitro vasodilator. Lowering of extra cellular Ca2+ in the physiological saline solution to 1/4 of normal selectively attenuated the vasorelaxant response of SNP, thereby causing an increase in its EC50 (2.4 x 10(-6) M; 95% CL, 1.23-4.68 x 10(-6) M, n = 4). Exposure of the tissues to high K+ (80 mM) solution, a protocol adopted to reduce the K+ gradient across the cell membrane, markedly inhibited the coronary artery relaxations induced by SNP (EC50, 2.54 x 10(-6) M; 95% CL, 1.31-4.91 x 10(-6) M, n = 4), when compared with tissues contracted with low K+ (30 mM) solution (EC50 7.9 x 10(-8); 95% CL, 4.4 x 10(-8)-1.44 x 10(-7) M, n = 6). The results suggested that a major component of SNP-induced relaxation of goat coronary artery was mediated by K(Ca) channels.
