Alterations in Metabolism and Diurnal Rhythms following Bilateral Surgical Removal of the Superior Cervical Ganglia in Rats

Abstract

Mammalian circadian rhythms are controlled by a master pacemaker located in the suprachiasmatic nuclei (SCN), which is synchronized to the environment by photic and nonphotic stimuli. One of the main functions of the SCN is to regulate peripheral oscillators to set temporal variations in the homeostatic control of physiology and metabolism. In this sense, the SCN coordinate the activity/rest and feeding/fasting rhythms setting the timing of food intake, energy expenditure, thermogenesis, and active and basal metabolism. One of the major time cues to the periphery is the nocturnal melatonin, which is synthesized and secreted by the pineal gland. Under SCN control, arylalkylamine N-acetyltransferase (AA-NAT)—the main enzyme regulating melatonin synthesis in vertebrates—is activated at night by sympathetic innervation that includes the superior cervical ganglia (SCG). Bilateral surgical removal of the superior cervical ganglia (SCGx) is considered a reliable procedure to completely prevent the nocturnal AA-NAT activation, irreversibly suppressing melatonin rhythmicity. In the present work, we studied the effects of SCGx on rat metabolic parameters and diurnal rhythms of feeding and locomotor activity. We found a significant difference between SCGx and sham-operated rats in metabolic variables such as an increased body weight/food intake ratio, increased adipose tissue, and decreased glycemia with a normal glucose tolerance. An analysis of locomotor activity and feeding rhythms showed an increased daytime (lights on) activity (including food consumption) in the SCGx group. These alterations suggest that superior cervical ganglia-related feedback mechanisms play a role in SCN-periphery phase coordination and that SCGx is a valid model without brain-invasive surgery to explore how sympathetic innervation affects daily (24 h) patterns of activity, food consumption and, ultimately, its role in metabolism homeostasis.

Characterization of a cell bridge variant connecting the nodose and superior cervical ganglia in the mouse: Prevalence, anatomical features, and practical implications

“…However, the existence of a cell bridge linking the NG and SCG led us to wonder if a solution injected into the NG could diffuse to the SCG, thereby leading to the unwanted “contamination” of sympathetic neurons. This is important considering that SCG neurons influence a wide range of autonomic and metabolic functions including food intake (Mul Fedele, Galiana, Golombek, Munoz, & Plano, 2017) and cardiovascular functions (Witt et al, 2017), among other examples. Moreover, because the cell bridge is only present in a subset of animals, and more frequently in males, the unwarranted contamination of SCG neurons may introduce experimental variability and false cases of gender differences.…”

Rest‐Activity Pattern Alterations in Idiopathic REM Sleep Behavior Disorder

“…According to the Braak staging hypothesis, Lewy bodies originates from the olfactory bulb and/or brainstem, and then progress to other brain regions 46 . In Braak stage 2, when RBD symptoms emerge, Lewy bodies may have already affected some critical components (eg, locus coeruleus, raphe nucleus, and pedunculopontine nucleus) of the ascending arousal system, 43,47 and circadian pathways (mainly through raphe nucleus and superior cervical ganglia) 48 . With more advanced stages, more components of arousal (eg, tuberomammillary nucleus and basal forebrain) 43–46 and circadian systems (eg, suprachiasmatic nucleus) 11,49 may present with pathological changes.…”

Reperfusion Arrhythmias Increase after Superior Cervical Ganglionectomy Due to Conduction Disorders and Changes in Repolarization

“…Our results confirm the physiological importance of rhythmic melatonin secretion, without removing the pineal gland or using any antiadrenergic agent. Although bilateral superior cervical ganglionectomy (SCGx) is a surgical procedure, this technique is less invasive than pinealectomy [17,19]. On the other hand, SCGx is more selective than a pharmacological adrenergic blockade.…”

“…Bilateral superior cervical ganglionectomy (SCGx) was performed as previously described [17,19,20,54]. Briefly, under ketamine/xylazine anesthesia (50 mg/kg of body weight and 5 mg/kg of body weight, respectively), the ventral neck region was shaved and disinfected.…”