Paraventricular nucleus modulates autonomic and neuroendocrine responses to acute restraint stress in rats

Abstract

The paraventricular nucleus of the hypothalamus (PVN) has been implicated in several aspects of neuroendocrine and cardiovascular control. The PVN contains parvocellular neurons that release the corticotrophin release hormone (CRH) under stress situations. In addition, this brain area is connected to several limbic structures implicated in defensive behavioral control, as well to forebrain and brainstem structures involved in cardiovascular control. Acute restraint is an unavoidable stress situation that evokes corticosterone release as well as marked autonomic changes, the latter characterized by elevated mean arterial pressure (MAP), intense heart rate (HR) increases and decrease in the tail temperature. We report the effect of PVN inhibition on MAP and HR responses, corticosterone plasma levels and tail temperature response during acute restraint in rats. Bilateral microinjection of the nonspecific synaptic blocker CoCl(2) (1 mM/100 nL) into the PVN reduced the pressor response; it inhibited the increase in plasma corticosterone concentration as well as the fall in tail temperature associated with acute restraint stress. Moreover, bilateral microinjection of CoCl(2) into areas surrounding the PVN did not affect the blood pressure, hormonal and tail vasoconstriction responses to restraint stress. The present results show that a local PVN neurotransmission is involved in the neural pathway that controls autonomic and neuroendocrine responses, which are associated with the exposure to acute restraint stress.

Thermal Imaging to Study Stress Non-invasively in Unrestrained Birds

“…The fast frame rate of the thermal videoing technique was able to show a drop in eye-region temperature of approximately 2 °C in 10 sec followed by a subsequent rise in temperature to within 0.5 °C of baseline within 3 min. Although peripheral cooling in response to mild stress has been recorded previously at around 1 min intervals 17,26,32 , the technique here showed that maximum drop in temperature may be extremely rapid. With lower time resolution the magnitude of this effect may be missed.…”

“…In response to a well-established acute mild stressor to an animal we expected rapid changes in the pattern of blood flow, from the periphery to the core via sympathetically mediated vasoconstriction that reduces skin temperature 17 . The periorbital region was chosen as this provided the only region of the body that was uninsulated and is associated with a rich intermingled network of small blood vessels, the rete ophthalmicum that can affect the heat loss from the eye 31 .…”

“…Within the same mechanism that generates SIH, though, lies yet another potential marker of stress: the peripheral vasoconstriction that moves blood, and with it heat, to the core simultaneously cools the skin 17 . Unlike core temperature, skin temperature can be measured completely non-invasively, by infrared thermography (IRT).…”

“…SIH typically raises core body temperature by 0.5-1.5 °C within 10-15 min of an acute stressor 10 . It is a relatively well documented phenomenon that a commonly applied experimental stressor of catching and handling an animal can raise core body temperature in a range of mammal and bird species [11][12][13][14][15][16][17] . Importantly, SIH correlates with other established indicators of stress, such as heart rate 18 , glucocorticoid levels 19 and behavior 20,21 .…”

Avian maternal response to chick distress

“…It has been suggested that this mechanism might have two functions; to redistribute blood to more important organs (e.g. the muscles and brain) and to prevent blood loss owing to potential injuries in the peripheries [26]. Decreased surface body temperature has been found in response to apparent emotional stress in sheep [27] and cattle [18].…”