Abstract
The lateral habenula (LHb) has an important role in the behavioural response to salient, usually aversive, events. We previously demonstrated that activation of neurons in the LHb increases brown adipose tissue (BAT) thermogenesis and constricts the cutaneous vascular bed, indicating that the LHb contributes to the central control of sympathetic outflow to thermoregulatory effector organs. We have now investigated whether the LHb mediates BAT thermogenesis elicited by emotional stress, and whether the LHb modulates thermoregulatory sympathetic outflow via the rostral medullary raphé, a key integrative lower brainstem sympathetic control centre. In conscious animals, lesioning the LHb attenuated emotional BAT thermogenesis, suggesting that the LHb is part of the central circuitry mediating emotional hyperthermia. In anesthetized animals, inhibition of neurons in the rostral medullary raphé reversed BAT thermogenesis and cutaneous vasoconstriction elicited by activation of neurons in the LHb, indicating that the LHb-induced autonomic responses are mediated through activation of the rostral medullary raphé neurons. The latency to activate BAT sympathetic discharge from electrical stimulation of the LHb was substantially greater than the corresponding latency after stimulation of the medullary raphé, suggesting that the neuronal pathway connecting those two nuclei is quite indirect.
Highlights
The lateral habenula (LHb) has an important role in the behavioural response to salient, usually aversive, events
The LHb-elicited increase in brown adipose tissue (BAT) thermogenesis contributed to a rise in body temperature
Our present result in conscious unrestrained rats shows that prior destruction of the LHb reduces the intensity of the rise in body temperature elicited by a salient, threatening, environmental situation, and that reduced BAT thermogenesis contributes to this reduced emotional hyperthermia
Summary
The lateral habenula (LHb) has an important role in the behavioural response to salient, usually aversive, events. Physiological responses to the same situations include an increase in body temperature, referred to as emotional hyperthermia or stress-induced hyperthermia, mediated by a combination of BAT thermogenesis and tail artery vasoconstriction, similar to the response obtained by stimulation of the LHb in anesthetized animals[4, 9, 10]. This suggests that the LHb may form part of the brain circuitry mediating emotional hyperthermia. To provide information concerning the central neural pathways whereby the LHb controls thermoregulatory sympathetic discharge, we used peri-stimulus averaged potential to compare the latencies to activation of BAT sympathetic discharge from the LHb and from the medullary raphe
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