Are imidazoline receptors involved in sympathetic neurotransmission in rat vas deferens |
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| Affiliation: | 1. University of São Paulo, Institute of Biomedical Sciences-I, Department of Physiology and Biophysics, São Paulo, Brazil;2. Nuclear and Energy Research Institute (IPEN), Biotechnology Center, São Paulo, Brazil;1. Laboratório de Microscopia Celular e Tecidual, Programa de Pós-graduação em Biologia Estrutural e Funcional, Departamento de Morfologia, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil;2. Departamento de Ciências Morfofisiológicas, Universidade Estadual de Maringá, Maringá, PR, Brazil;3. Faculdade de Medicina Veterinária, Centro Universitário Monte Serrat (UNIMONTE), Santos, São Paulo, Brazil;4. Laboratório de Histologia, Departamento de Morfologia, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil;5. Departamento de Anatomia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brazil;6. Universidade Federal do Piauí, Campus Senador Helvídio Nunes de Barros, Picos, PI, Brazil;1. School of Physical Education and Sport, University of Sao Paulo, Brazil;2. K.G. Jebsen Center of Exercise in Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway;3. Heart Institute, Faculty of Medicine, University of Sao Paulo, Brazil;4. Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, Brazil;1. Superior Institute of Biomedical Sciences, State University of Ceará, Brazil;2. Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil;3. Department of Biophysics and Physiology, Federal University of Piauí, Brazil;1. Department of Pathology, School of Veterinary Medicine, University of São Paulo, São Paulo 05508-270, Brazil;2. Laboratory of Chemical Neuroanatomy, Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508-000, Brazil;3. Center for Neuroscience and Behavior, Institute of Psychology, University of São Paulo, Sao Paulo 05508-030, Brazil |
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| Abstract: | - 1.1. An involvement of imidazoline receptors in the modulation of neurotransmitter release was investigated in the prostatic portion of the rat vas deferens stimulated transmurally at 0.2 Hz or by single pulses.
- 2.2. Idaxozan and yohimbine induced a concentration-dependent potentiation of the contractile response to 0.2-Hz transmural stimulation in the epididymal and prostatic portion of the vas.
- 3.3. After reserpine treatment, idazoxan, but not yohimbine, still potentiated the contractile response, suggesting a possible involvement of imidazoline receptors.
- 4.4. Clonidine and rilmenidine, agonists with different affinities to α2-adrenoceptors and imidazoline receptors, inhibited with the same potency the contractile responses to a single pulse transmural stimulation.
- 5.5. Yohimbine (a selective α2-adrenoceptor antagonist) antagonized the inhibitory concentration effect curve to rilmenidine in a competitive manner. pA2 values for idaxozan (an antagonist to α2-adrenoceptors and imidazoline receptors) were not different when noradrenaline or rilmenidine were used as agonists. Phenoxybenzamine blocked the effect of both agonists.
- 6.6. Thus, the potency relationship of agonists, as well as the effect of the antagonists, did not favor the hypothesis that imidazoline receptors are involved in the idazoxan-potentiating effect in the rat vas deferens.
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