RESUMO
The pain sensation system is highly conserved among species, thus animal models have been used to investigate relevant tissues. The focus for head-specific pain has been on the primary nociceptive neurons in the trigeminal pathway, i.e. trigeminal ganglia. The secondary nociceptive neurons of the trigeminal pathway, trigeminal nucleus caudalis (TNC), have not been assessed. We expect different gene expression profiles compared to the homologous spinal cord dorsal horn (SDH), as several signalling substances provoke head-specific pain but not peripheral pain. We aim to provide expression profiles of TNC and SDH, tissues highly relevant for pain- and migraine-studies. We extracted RNA from laser capture microdissected laminae I-V from TNC and SDH from six Wistar rats for RNA-Sequencing. We showed the expression profiles of genes involved in neural signal transmission and found that among all G protein-coupled receptors Gabbr1 was highest expressed in both tissues. Among the migraine-associated genes we showed that Cacna1a, where non-synonyms mutations can cause familial hemiplegic migraine, was highly expressed with a slightly lower expression in TNC than in SDH. To show the genetic differences between the two homologous systems we performed a differential expression analysis, revealing 1696 genes higher and 1895 genes lower expressed genes in TNC than in SDH, of which many were neuronal-related. The high number of differentially expressed genes shows the large genetic difference between the trigeminal and spinothalamic system. Our results contribute to the characterization of nociceptive pathways, which may help us understanding why several signalling molecules cause headache and no peripheral pain.
Assuntos
Perfilação da Expressão Gênica/métodos , Corno Dorsal da Medula Espinal/metabolismo , Núcleo Inferior Caudal do Nervo Trigêmeo/metabolismo , Animais , Expressão Gênica/fisiologia , Microdissecção e Captura a Laser , Masculino , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Neurotransmissores/genética , Neurotransmissores/metabolismo , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Receptores de Neurotransmissores/genética , Receptores de Neurotransmissores/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia , Sinapses/genética , Sinapses/metabolismoRESUMO
INTRODUCTION: Infusion of glyceryl trinitrate (GTN), a donor of nitric oxide, induces immediate headache in humans that in migraineurs is followed by a delayed migraine attack. In order to achieve increased knowledge of mechanisms activated during GTN-infusion this present study aims to investigate transcriptional responses to GTN-infusion in the rat trigeminal ganglia. METHODS: Rats were infused with GTN or vehicle and trigeminal ganglia were isolated either 30 or 90 minutes post infusion. RNA sequencing was used to investigate transcriptomic changes in response to the treatment. Furthermore, we developed a novel method for Gene Set Analysis Of Variance (GSANOVA) to identify gene sets associated with transcriptional changes across time. RESULTS: 15 genes displayed significant changes in transcription levels in response to GTN-infusion. Ten of these genes showed either sustained up- or down-regulation in the 90-minute period after infusion. The GSANOVA analysis demonstrate enrichment of pathways pointing towards an increase in immune response, signal transduction, and neuroplasticity in response to GTN-infusion. Future functional in-depth studies of these mechanisms are expected to increase our understanding of migraine pathogenesis.