TY - JOUR
T1 - The toad iris assay
T2 - A simple method for evaluating CRH action on the sympathetic nervous system
AU - Carr, James A.
AU - Zozzaro, Paula E.
PY - 2004/1/1
Y1 - 2004/1/1
N2 - Corticotropin-releasing hormone (CRH) plays a key role in the regulation of stress and arousal associated behaviors in mammals, and contributes to hyperglycemia and activation of the sympathetic nervous system (SNS) during stress. Whether CRH regulates SNS activity in nonmammals has not been well studied. Here we used the iris assay to determine the ability of ovine CRH (oCRH) to influence SNS activity in the Texas toad, Bufo speciosus. In the toad iris assay, relaxation of the sphincter pupillae muscles in the iris is determined by measuring treatment-related changes in pupillary dilatation. A single dose of oCRH administered via the dorsal lymph sac increased pupillary dilatation within 30min after administration. The stimulatory effects of oCRH on pupillary dilatation were dose- and time-dependent, were blocked with the CRH-receptor antagonist α-helical CRH, were associated with elevated plasma norepinephrine, and were not blocked by hypophysectomy. Isoproterenol, a β-adrenergic receptor agonist, increased pupillary dilatation in a dose-related fashion. The effects of isoproterenol and oCRH were blocked by the β-adrenergic receptor antagonist propranolol. We conclude that the toad iris assay is a simple but effective method for assessing CRH receptor regulation of the SNS.
AB - Corticotropin-releasing hormone (CRH) plays a key role in the regulation of stress and arousal associated behaviors in mammals, and contributes to hyperglycemia and activation of the sympathetic nervous system (SNS) during stress. Whether CRH regulates SNS activity in nonmammals has not been well studied. Here we used the iris assay to determine the ability of ovine CRH (oCRH) to influence SNS activity in the Texas toad, Bufo speciosus. In the toad iris assay, relaxation of the sphincter pupillae muscles in the iris is determined by measuring treatment-related changes in pupillary dilatation. A single dose of oCRH administered via the dorsal lymph sac increased pupillary dilatation within 30min after administration. The stimulatory effects of oCRH on pupillary dilatation were dose- and time-dependent, were blocked with the CRH-receptor antagonist α-helical CRH, were associated with elevated plasma norepinephrine, and were not blocked by hypophysectomy. Isoproterenol, a β-adrenergic receptor agonist, increased pupillary dilatation in a dose-related fashion. The effects of isoproterenol and oCRH were blocked by the β-adrenergic receptor antagonist propranolol. We conclude that the toad iris assay is a simple but effective method for assessing CRH receptor regulation of the SNS.
KW - Amphibian
KW - Anuran
KW - Corticotropin-releasing hormone
KW - Iris
KW - Stress
KW - Sympathetic nervous system
UR - http://www.scopus.com/inward/record.url?scp=0345255953&partnerID=8YFLogxK
U2 - 10.1016/j.ygcen.2003.09.011
DO - 10.1016/j.ygcen.2003.09.011
M3 - Article
C2 - 14644653
AN - SCOPUS:0345255953
VL - 135
SP - 134
EP - 141
JO - General and Comparative Endocrinology
JF - General and Comparative Endocrinology
SN - 0016-6480
IS - 1
ER -