Arousal and differential Fos expression in histaminergic neurons of the ascending arousal system during a feeding‐related motivated behaviour

Abstract

Arousal depends on the concerted activity of the ascending arousal system (AAS) but specific stimuli may primarily activate some nuclei of this system. Motivated behaviours are characterized by behavioural arousal, although it is not known which AAS nuclei are active during a motivated behaviour. To address this issue, rats were rendered motivated for food by fasting them for 1 day and then were enticed with food that they could not obtain for varying periods of time. We studied the level of arousal by polysomnography or radiotelemetry, and Fos-ir in the AAS, during food enticing. We found a strong arousal and an early increase in Fos-ir in the histaminergic neurons from the tuberomammillary nucleus, after 30 min of enticing, followed by increased Fos-ir in the whole AAS if food enticing was prolonged to 1 or 2 hours. In contrast, food presentation to non-motivated rats did not increase arousal or Fos-ir in the tuberomammillary nucleus. As opposed to the active arousal of the motivated rats, passive arousal induced by sensory stimulation was associated with increased Fos-ir in the locus coeruleus and the orexin neurons, but not with increased Fos-ir in the tuberomammillary nucleus or in the other nuclei of the AAS. We conclude that the arousal during feeding-related motivated behaviour is associated primarily with the activation of the tuberomammillary nucleus, while the other arousal-related nuclei become active later on.

Histamine in the brain: Beyond sleep and memory

“…For as much as it may seem that the role of the histaminergic system is redundant in modulating the sleepwake cycle, it is becoming clear that histamine in the brain finely orchestrates diverse aspects of behavioral responses that require an aroused state. For example, histamine supposedly drives food intake by increasing the arousal state of the animal [58], and secondary to arousing the animal, histamine coordinates satiety and the consolidation of temporal information associated with food consumption [74,75]. Augmented histamine release is also an indicator of stress and disrupting the spatiotemporal specificity of histamine release may contribute to maladaptive behavioral responses.…”

“…Recently, it has become clear that food-anticipatory activity exhibits the characteristics of a circadian rhythm, although determining the anatomic location of the food-entrainable oscillator (FEO) has been very difficult. Histamine drives feeding anticipating arousal, an important actor in the FEO, and is probably involved in numerous other feeding related processes [58]. In fact, while the effects of the histaminergic system in the modulation of the consummatory phase of feeding have been…”

“…The appetitive phase of motivated behaviors has distinctive preparatory physiological changes, such as increases in behavioral arousal [59] and core temperature [58]. Therefore, the histaminergic system is a good candidate to promote arousal during the appetitive state (Fig.…”

“…These data made it clear that histamine controls heterogeneous aspects of feeding. Presumably, histamine drives food intake by increasing the arousal state of the animal [58]. Secondary to arousing the animal, brain histamine seems to coordinate satiety and the consolidation of temporal information associated with food consumption [74,75].…”

A final common pathway for depression? Progress toward a general conceptual framework

“…Moreover it was consistent with the hypothesis advanced by Weiss et al (1998) of stress-induced inhibition of the NAC, and with the view advanced by Gold & Chrousos (2002) that stressful stimulation leads to a suppression of physiological activities that are not essential to immediate survival which include many positively motivated behaviors such as reproduction, feeding, exploration and growth. Neural pathways that are capable of mediating interactions between the stress and positive networks include cortical regions that have descending inhibitory projections to stress areas (Spencer and Day, 2004;Amat et al, 2005;Barbas et al, 2003), and efferents from stress regions to aminergic activating nuclei in the brainstem and midbrain (Valdés et al, 2005;Reyes et al, 2005;Forray and Gysling, 2004;Van Bockstaele et al, 1999;Weiss et al, 2005).…”