Differential contribution of calcium channels to α1-adrenoceptor-mediated contraction is responsible for diverse responses to cooling between rat tail and iliac arteries

Involvement of α1B-adrenoceptors and Rho kinase in contractions of rat aorta and mouse spleen

“…In rat aorta, contractions to both phenylephrine [ 9 ] and angiotensin II [ 10 ] involve Rho kinase. In rat tail artery, cooling increases contractions to the α 1 -adrenoceptor agonist phenylephrine at least partly via Rho kinase [ 11 ]. Conversely, in rat aorta, cooling decreases contractions to phenylephrine, involving inhibition of Rho kinase [ 12 ].…”

Mechanism of Membrane Depolarization Involved in α_1A-Adrenoceptor-Mediated Contraction in Rat Tail and Iliac Arteries

“…This is the first report, to our knowledge, to provide evidence for the mechanism for α 1A -adrenoceptor-mediated depolarization in tail and iliac arterial smooth muscle cells. Less contribution of VDCC to phenylephrine-induced contraction in tail arteries compared to in iliac arteries, shown in our previous study, 5,6) might be due to that phenylephrine-induced activation of VDCC is caused only by depolarization via cation influx through the activation of LOE908-sensitive non-selective cation channels via α 1Aadrenoceptors in tail arteries.…”

“…Our previous studies have suggested that the contribution of VDCC to α 1A -adrenoceptor-meidated contraction is less than that to α 1D -adrenoceptor-mediated one and that phenylephrineinduced contraction is mediated via mostly α 1A -adrenoceptors in tail arteries and via both α 1A -and α 1D -adrenoceptors in iliac arteries. 5,6) Martí et al have demonstrated using quantitative RT-PCR that both α 1A -and α 1D -adrenoceptors are expressed in a similar level in iliac arteries, whereas α 1A -adrenoceptors are highly expressed in tail arteries. 9) The present study showed that nifedipine barely affected the contraction induced by the α 1A -adrenoceptor selective agonist A-61603 in the presence of LOE908 in iliac arteries.…”

“…1) Although α 2C -adrenoceptors have been proposed to be involved in the enhanced contractile response, [2][3][4] our previous studies showed that α 1A -adrenoceptors also contribute to the enhancement at low temperature in rat tail arteries. 5) In addition, a well correlation between the enhanced contractile response to phenylephrine at low temperature and the expression level of α 1A -adrenoceptors was accompanied with a less contribution of voltage-dependent Ca 2+ channels (VDCC) to the contraction induced by phenylephrine in rat tail arteries. 6) VDCC is well known to be suppressed at low temperature.…”

“…On the other hand, we also found that VDCC contributes to the part of contraction mediated via α 1A -adrenoceptors in rat tail arteries. 5) The tail artery plays a role for thermoregulation as a typical cutaneous artery, whereas the iliac artery is a visceral artery and supplies blood to the pelvis, legs and tail. The expression patterns of α 1 -adrenoceptor subtypes have been shown to be different between these arteries of Wistar rats; α 1Aadrenoceptors are prominent in the tail artery, whereas both α 1A -and α 1D -subtypes are expressed at similar levels in the iliac artery.…”