Enhanced vasoconstrictor responses in renal and femoral arteries of the golden hamster during hibernation

Abstract

1. The present study assessed local regulation of vascular tone of euthermic (control), cold control and hibernating golden hamsters. Sympathetic neurotransmission in the renal artery, the long term effects of hibernation on perivascular nerve activity, and the responsiveness of femoral artery to a number of neurotransmitters and hormones with both constrictor and dilator actions during hibernation are described. 2. The contractile responses of the renal arterial rings to transmural nerve stimulation (80 V, 0.1 ms, 4-64 Hz, for 1 s) were negligible in controls, significantly increased at higher frequencies of stimulation in cold controls and markedly enhanced in the hibernating group at all frequencies tested. The contractile responses to exogenous noradrenaline (NA; 0.1-100 microM) were significantly increased in the renal arteries of hibernating hamsters compared with controls, but not compared with cold controls. Responses to exogenous ATP (1-3000 microM) and KCl (120 mM) were similar among all experimental groups. 3. The maximal contractile responses of femoral arterial rings to the sympathetic co-transmitter ATP and 5-hydroxytryptamine were increased by approximately 124% and 99%, respectively, in hibernating compared with cold control preparations without a change in the concentration of agonist that produces half-maximal response. However, the responses to NA were not altered during hibernation. 4. Vasoconstriction of femoral arterial rings in response to arginine vasopressin was significantly enhanced in both cold controls and hibernating groups, while vasoconstriction in response to endothelin-1 and KCl was unaltered. 5. The dilator responses of femoral arterial rings to acetylcholine, sodium nitroprusside and adenosine were not different among the groups. 6. It is suggested that the marked augmentation of sympathetic neurotransmission, selective supersensitivity of the vascular smooth muscle to sympathetic contractile agents and unaltered vasodilatory mechanisms may provide a means for maintenance of vascular tone and peripheral resistance during hibernation.

Figure 1. Frequency-response recordings for transmural nerve stimulation

Recording of a typical experiment showing vasoconstrictor responses to transmural nerve stimulation (80 V, 0.1 ms, 4–64 Hz, for 1 s) in hamster renal arteries taken from control (top panel), cold control (middle panel) and hibernating (bottom panel) animals.

Figure 2. Frequency-response relationship in hamster renal arteries

Frequency-response curves to transmural nerve stimulation (80 V, 0.1 ms, 4–64 Hz, for 1 s) taken from controls (•, n = 5), cold controls (○, n = 7) and hibernating hamsters (□, n = 5). *P < 0.05, **P < 0.01vs. control; †P < 0.05vs. cold control.

Figure 3. Different components of frequency-response relationship in hamster renal arteries

Frequency-response to transmural nerve stimulation (80 V, 0.1 ms, 4–64 Hz, for 1 s) in the absence (▪) and in the presence of prazosin (1 μm, ), and prazosin (1 μm) plus α,β-methylene ATP (1 μm, ) taken from controls (n = 5) (A), cold controls (n = 7) (B) and hibernating hamsters (n = 5) (C).

Figure 4. Concentration-response relationship for exogenous neurotransmitters in hamster renal artery

Concentration-response curves showing vasoconstrictor responses to noradrenaline (NA, A) and ATP (B) of arterial rings taken from controls (•, n = 6), cold controls (○, n = 7) and hibernating animals (□, n = 4). *P < 0.05vs. control.

Figure 5. Concentration-response relationship for contractile neurotransmitters in hamster femoral artery

Concentration-response curves showing vasoconstrictor responses to NA (A), ATP (B) and 5-HT (C) in isolated arterial rings taken from hibernating (□), cold control (○) and control (•) hamsters. All results are expressed as means ± s.e.m. n = 4–5. *P < 0.05, **P < 0.01vs. control.

Figure 6. Concentration-response relationship for contractile peptides in hamster femoral artery

Concentration-response curves showing vasoconstrictor responses to AVP (A) and ET-1 (B) in isolated arterial rings taken from hibernating (□), cold control (○) and control (•) hamsters. All results are expressed as means ± s.e.m. n = 4–6.

Figure 7. Concentration-response relationship for vasodilator agents in hamster femoral artery

Concentration-response curves showing vasodilator responses to ACh (A), SNP (B) and adenosine (C) in isolated arterial rings precontracted by NA, taken from hibernating (□), cold control (○) and control (•) hamsters. All results are expressed as means ± s.e.m. n = 4–6.