RESUMEN
We have isolated and characterized the cDNAs for nitric oxide synthase (NOS) and soluble guanylyl cyclase (sGC) from the terrestrial slug Limax marginatus, and examined the presence and distribution of their mRNAs in the central nervous system using histological techniques and a reverse transcription-polymerase chain reaction method. Our results showed that both bursting and nonbursting neurons in the procerebral lobes contain the mRNAs for both NOS and sGC. We further found that the oscillation frequency of electrical activity in the procerebral lobes increases with increasing intracellular concentrations of cyclic GMP (cGMP). Taken together with previous data on the NO-induced cGMP-like immunoreactivity and on the anatomical distribution of neurites and the localization of synapses of bursting and nonbursting neurons, our present results suggest that NO-induced changes in cGMP concentration modulate the oscillation frequency in the procerebral lobes by acting on the olfactory input pathways, but possibly not on the output pathways, in slugs. .
Asunto(s)
Relojes Biológicos/genética , Sistema Nervioso Central/enzimología , Moluscos/enzimología , Óxido Nítrico Sintasa/metabolismo , Vías Olfatorias/enzimología , Receptores Citoplasmáticos y Nucleares/metabolismo , Potenciales de Acción/genética , Secuencia de Aminoácidos/genética , Animales , Secuencia de Bases/genética , ADN Complementario/análisis , ADN Complementario/genética , Ganglios de Invertebrados/enzimología , Guanilato Ciclasa , Datos de Secuencia Molecular , Vías Nerviosas/enzimología , Óxido Nítrico Sintasa/genética , Óxido Nítrico Sintasa/aislamiento & purificación , Filogenia , Estructura Terciaria de Proteína/genética , Subunidades de Proteína/genética , Subunidades de Proteína/aislamiento & purificación , Subunidades de Proteína/metabolismo , Receptores Citoplasmáticos y Nucleares/genética , Receptores Citoplasmáticos y Nucleares/aislamiento & purificación , Homología de Secuencia de Aminoácido , Homología de Secuencia de Ácido Nucleico , Guanilil Ciclasa SolubleRESUMEN
To examine the distribution of nitric oxide (NO)-generative cells and NO-responsive cells in the tentacles and procerebral lobes (olfactory processing center) of terrestrial slugs, we applied NADPH diaphorase (NADPH-d) histochemistry and NO-induced cyclic GMP (cGMP)-like immunohistochemistry. We found that NADPH-d reactive cells/fibers and cGMP-like immunoreactive cells/fibers were different, but they were localized adjacent to each other, in both the tentacles and the procerebral lobes. Then, we measured the concentration of NO that was generated around the procerebral lobes using an NO sensitive electrode, when the olfactory nerve was electrically stimulated as a replacement for an odorant stimulus. Stimulation of the olfactory nerve evoked an increase in NO concentration at nanomolar levels, suggesting that binding of nanomolar concentrations of NO to the prosthetic heme group activates soluble guanylyl cyclase. Taken together with previously reported physiological data, our results, therefore, showed that the NO/cGMP pathways are involved in slug olfactory processing.
