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.

Seasonal decrease in thermogenesis and increase in vasoconstriction explain seasonal response to N6‐cyclohexyladenosine‐induced hibernation in the Arctic ground squirrel (Urocitellus parryii)

“…Increased vasoconstriction described here and by others during fasting‐induced torpor in mice and hibernation in ground squirrels and hamsters (Lyman and O’brien ; Lyman and O’Brien, ; Karoon et al, ; Swoap and Gutilla, ) decreases conductive heat loss in Winter AGS after CHA treatment. CHA induces an immediate drop in O 2 consumption, followed by a delayed decrease in T b in Winter AGS.…”

“…A seasonal decrease in euthermic T b followed by a decrease in thermogenesis precedes the onset of the hibernation season (Sheriff et al, ; Frare et al, ), which coincides with a circannual increase in sleep in euthermic ground squirrels (Walker et al, ) and an increase in vasoconstriction (Karoon et al, ; Swoap and Gutilla, ). Vasoconstriction, sleep, and the decrease in thermogenesis are seasonal strategies employed to achieve energy conservation during hibernation.…”

Autonomic Neurotransmission: 60 Years Since Sir Henry Dale

“…In a series of studies on hibernation, we showed that changes in expression of transmitters and associated enzymes occurred in both the cardiovascular and visceral systems of hibernating hamsters (77)(78)(79). For example, NOS-positive and endothelin-positive endothelial cells were significantly lower than those observed in active, cold-exposed, or aroused animals, whereas there was an increase in TH-and NPY-immunoreactive perivascular nerves.…”

Differential Effects of Cold Exposure on Muscle Fibre Composition and Capillary Supply in Hibernator and Non‐Hibernator Rodents

“…They are often capable of normal activity at low temperatures, relying on increased thermogenesis in visceral organs, adipose tissue and skeletal muscle to regulate core temperature (Jansky, 1973). This elevated aerobic metabolism is likely to require adaptive changes in peripheral oxygen transport, for example vascular adaptations which moderate changes in blood pressure and total peripheral resistance at low temperatures (Brown et al 1993;Karoon et al 1998).…”