Cardiorespiratory function is altered by picomole injections of 5'-N-ethylcarboxamidoadenosine into the nucleus tractus solitarius of rats.

摘要: Abstract A limited occipital craniotomy was conducted on urethane-anesthetized, spontaneously breathing rats to expose the caudal medulla in region of obex. Microinjections 5′- N -ethylcarboxamidoadenosine (NECA), an adenosine analog, were made into medial nucleus tractus solitarius (NTS) at level tip area postrema, NTS which there is known be a functional co-existence cardiovascular and respiratory-related neuronal elements. Cardiorespiratory responses subsequently recorded for 60 min test period. NECA, dose range 0.35–350 pmol per rat, produced significant dose-related reductions respiratory rate accompanied by dose-dependent increases tidal volume these pronounced effects respiration persisted throughout In contrast, NECA microinjections parameters this bidirectional elicited considerably more complex during During initial period (2–5 min) following injection, hypttension (at lower doses) pressor higher addition bradycardia whereas end period, almost all doses had resulted hypertension tachycardia. Multivariate analysis variance (MANOVA) correlation statistics indicated that blood pressure 2–5 unlikely related depression frequency. further examination data MANOVA pharmacological exhibited highly specific time-related response pattern respiratory, but not cardiovascular, parameters. Taken together, manifold patterns suggest may mediated different intrinsic mechanisms than are NECA. At administration remained profoundly depressed. view previous studies showing cyclic AMP analogs, forskolin, isoproterenol same sites elicit similar respiration, results with present study support notion serve as second messenger control regions depressant single receptor subtype. On other hand, contrast wherein itself relatively brief hypotension NTS, from show metabolically stable analog adenosine, exert prolonged multiplex modulatory influences intact rat. The possibility mixed agonist subtypes, thereby influence activating one population subtypes elements NTS. Finally, potent plays neuromodulatory role brainstem cardiorespiratory regions. findings over time also lend case using vivo models assess actions neuroactive agents.