Neurophamacology of Yawning

Abstract

Yawning is a common behavioral event that is observed in humans, as well as other mammals, birds and reptiles. In humans, yawning often occurs just before bed and upon waking up, and is also associated with tedious or boring situations. Although the physiologic roles of yawning have yet to be fully elucidated, the past 50 years of research has led to a much greater understanding of the neuropharmacologic regulation of yawning. While many of the early studies concluded that yawning was primarily driven by changes in cholinergic neurotransmission, we now know that numerous neurotransmitters and neurohormones are involved in the mediation of yawning, including acetylcholine, dopamine, glutamate, serotonin, oxytocin, GABA, opioids, adrenergics, nitric oxide, as well as the proopiomelanocortin-derived peptides ACTH and alpha-MSH. Furthermore, antagonist interaction studies have clearly defined at least 3 distinct neural pathways involved in the induction of yawning, as well as the hierarchical order through which these different neurotransmitter systems interact to regulate yawning. The following sections will discuss the state of knowledge for each of the major neurotransmitters and neurohormones involved in the regulation of yawning, their interactions with one another, and their place in the hierarchical organization of yawning.

Lorcaserin Reduces the Discriminative Stimulus and Reinforcing Effects of Cocaine in Rhesus Monkeys

“…The time course for yawning induced by 3.2 mg/kg lorcaserin closely matched plasma drug concentrations after administration of this dose, including the lack of behavioral effect and disappearance of lorcaserin in blood 24 hours after administration. These findings are consistent with a role for 5-HT 2C receptors in mediating the induction of yawning by drugs acting on 5-HT mechanisms (Pomerantz et al, 1993;Collins and Eguibar, 2010). In addition to yawning, larger doses of lorcaserin also decreased spontaneous activity and food-maintained responding in all monkeys and produced oral-facial stereotypies (i.e., abnormal tongue movements) in a subset of monkeys.…”

Central administration of oxytocin differentially increases yawning, penile erections and scratching in high- (HY) and low-yawning (LY) sublines of Sprague–Dawley rats

“…Of these neuropeptides, it is suggested that the magnitude of the effect is greatest with oxytocin (Argiolas and Melis, 1998;Collins and Eguibar, 2010). In fact, oxytocinergic neurons, in the paraventricular nucleus (PVN) of the hypothalamus, represent the key region for the induction of yawning and penile erections (Melis and Argiolas, 2011).…”

Involvement of dopaminergic and cholinergic pathways in the induction of yawning and genital grooming by the aqueous extract of Saccharum officinarum L. (sugarcane) in rats

“…Considering that yawning is also observed in anencephalic newborns having solely the medulla oblongata, the neural structures necessary for yawning are possibly located in brainstem regions that are either near or in the respiratory and vasomotor centers, specially those responsible for controlling facial mimicry, chewing, deglutition, breathing, and possibly stretching. This behavior may be spontaneously triggered, or it can occur in the presence of nausea, vomiting, tumors or brain injuries, hemorrhage, encephalitis, or after several neuropharmacological manipulations [9,10].…”

“…A series of neurotransmitters and neuropeptides exert central control over such behaviors. Amongst endogenous mediators, the best-known ones are dopamine; acetylcholine; oxytocin; adrenocorticotropin (ACTH); melanocyte stimulating hormone; serotonin; excitatory amino acids; nitric oxide; and opioid peptides [9][10][11].…”