ISSN:
1432-1912
Keywords:
Melatonin
;
UK-14304
;
Rat distal caudal artery
;
Juvenile rats
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Responses of isolated, 60 mmHg ‘pressurized’ segments of the distal caudal artery of adult and juvenile Wistar rats to melatonin and the selective α2-adrenoceptor agonist 5-bromo-6-[2-imidazolin-2-ylamino]-quinoxaline bitartrate (UK-14304) were examined using the Halpern pressure myograph. Melatonin showed no direct vasoconstrictor activity in vessels from adult rats, whereas UK-14304 produced moderate vasoconstriction (pD2- 7.43+-0.09). In the presence of phenylephrine-induced tone, melatonin produced a variable but small constrictor response (〈 10µm reduction in diameter) in some vessels; the response to 1 gmol/l UK-14304 was less than in the absence of tone. In vessels isolated from juvenile rats, melatonin caused concentration-dependent vasoconstriction with a maximum response about 70% of the maximum response elicited by UK-14304. Vessels from juvenile rats were more sensitive to melatonin(pD2- 9.40+-0.07) than they were to UK-14304 (pD2 -8.12+-0.14). In the presence of phenylephrine-induced tone, the vasoconstrictor responses to both melatonin and IK-14304 were markedly less; the sensitivity to melatonin was not different from that seen in the absence of tone. These findings indicate that ‘pressurized’ segments of the isolated distal caudal artery may provide a simple and convenient, functional model of melatonin receptors. The findings also appear to implicate melatonin in thermoregulatory processes in juvenile rats.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00173553
Permalink
