Hyperthyroidism changes nociceptive response and ecto-nucleotidase activities in synaptosomes from spinal cord of rats in different phases of development.
Changes in transport, receptors and production of extracellular adenosine have been observed after induction of hyperthyroidism. Adenosine is associated with inhibitory actions such as reduction in release of excitatory neurotransmitters and antinociception at spinal site. In contrast, ATP acts as an excitatory neurotransmitter and produces pronociceptive actions. ATP may be completely hydrolyzed to adenosine by an enzyme chain constituted by an ATP diphosphohydrolase and an ecto-5'-nucleotidase, as previously described in the spinal cord. Thus, we now investigated the effects of the hyperthyroidism on adenine nucleotide hydrolysis in the spinal cord and verified the nociceptive response in this pathology during different phases of development. Hyperthyroidism was induced in male Wistar rats, aged 5, 60 and 330 days by daily intraperitoneal injections of L-thyroxine (T4) for 14 days. Nociception was assessed with a tail-flick apparatus. Rats starting the treatment aged 5 days demonstrated a significant increase in ADP and AMP hydrolysis and increased tail-flick latency (TFL). In contrast, in the spinal cord from hyperthyroid rats aged 60 and 330 days old, the hydrolysis of ATP, ADP and AMP were significantly decreased. Accordingly, the tail-flick latency was decreased, indicating a hyperalgesic response. These results suggest the involvement of ecto-nucleotidases in the control of the hyperthyroidism-induced nociceptive response in rats at distinct developmental stages.
Bruno
Alessandra Nejar
AN
Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Avenida Ramiro Barcellos 2600-ANEXO, 90035-003, Porto Alegre, RS, Brazil.
Fontella
Fernanda Urruth
FU
Crema
Leonardo Machado
LM
Bonan
Carla Denise
CD
Dalmaz
Carla
C
Barreto-Chaves
Maria Luiza M
ML
Sarkis
João José Freitas
JJ
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D006980:Hyperthyroidism / Q000139:chemically induced / Q000201:enzymology* / Q000503:physiopathology*; D008297:Male; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D051381:Rats; D013116:Spinal Cord / Q000033:anatomy & histology / Q000201:enzymology* / Q000254:growth & development; D013574:Synaptosomes / Q000201:enzymology* / Q000378:metabolism; D013974:Thyroxine / Q000633:toxicity
D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C027201:ectoATPase; D013974:Thyroxine