RESUMEN
Sighs are long, deep breaths expressing sadness, relief or exhaustion. Sighs also occur spontaneously every few minutes to reinflate alveoli, and sighing increases under hypoxia, stress, and certain psychiatric conditions. Here we use molecular, genetic, and pharmacologic approaches to identify a peptidergic sigh control circuit in murine brain. Small neural subpopulations in a key breathing control centre, the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG), express bombesin-like neuropeptide genes neuromedin B (Nmb) or gastrin-releasing peptide (Grp). These project to the preBötzinger Complex (preBötC), the respiratory rhythm generator, which expresses NMB and GRP receptors in overlapping subsets of ~200 neurons. Introducing either neuropeptide into preBötC or onto preBötC slices, induced sighing or in vitro sigh activity, whereas elimination or inhibition of either receptor reduced basal sighing, and inhibition of both abolished it. Ablating receptor-expressing neurons eliminated basal and hypoxia-induced sighing, but left breathing otherwise intact initially. We propose that these overlapping peptidergic pathways comprise the core of a sigh control circuit that integrates physiological and perhaps emotional input to transform normal breaths into sighs.
Asunto(s)
Péptido Liberador de Gastrina/metabolismo , Neuroquinina B/análogos & derivados , Neuronas/fisiología , Receptores de Bombesina/metabolismo , Respiración , Transducción de Señal/fisiología , Animales , Bombesina/farmacología , Emociones/fisiología , Femenino , Péptido Liberador de Gastrina/deficiencia , Péptido Liberador de Gastrina/genética , Técnicas In Vitro , Masculino , Ratones , Ratones Endogámicos C57BL , Neuroquinina B/deficiencia , Neuroquinina B/genética , Neuroquinina B/metabolismo , Neuroquinina B/farmacología , Neuronas/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Respiración/efectos de los fármacos , Centro Respiratorio/citología , Centro Respiratorio/efectos de los fármacos , Centro Respiratorio/fisiología , Proteínas Inactivadoras de Ribosomas Tipo 1/farmacología , Saporinas , Transducción de Señal/efectos de los fármacosRESUMEN
Pulsatile gonadotropin-releasing hormone (GnRH) is crucial to normal reproductive function and abnormalities in pulse frequency give rise to reproductive dysfunction. Kisspeptin and neurokinin B (NKB), neuropeptides secreted by the same neuronal population in the ventral hypothalamus, have emerged recently as critical central regulators of GnRH and thus gonadotropin secretion. Patients with mutations resulting in loss of signaling by either of these neuroendocrine peptides fail to advance through puberty but the mechanisms mediating this remain unresolved. We report here that continuous kisspeptin infusion restores gonadotropin pulsatility in patients with loss-of-function mutations in NKB (TAC3) or its receptor (TAC3R), indicating that kisspeptin on its own is sufficient to stimulate pulsatile GnRH secretion. Moreover, our findings suggest that NKB action is proximal to kisspeptin in the reproductive neuroendocrine cascade regulating GnRH secretion, and may act as an autocrine modulator of kisspeptin secretion. The ability of continuous kisspeptin infusion to induce pulsatile gonadotropin secretion further indicates that GnRH neurons are able to set up pulsatile secretion in the absence of pulsatile exogenous kisspeptin.