Role of adrenergic neuronal activity in the yawning induced by tacrine and NIK-247 in rats

Yawning, a thermoregulatory mechanism during fever? A study of yawning frequency and its predictors during experimentally induced sickness

Yawning has been proposed to serve both physiological and social functions, the latter likely to have developed later in its evolution. A central hypothesis is that yawning cools the brain but whether yawning is a thermoregulatory mechanism that is activated during hyperthermia (i.e., thermoregulatory failure) or is activated in any instance of brain temperature increase (e.g., also during fever) is unclear and experimental assessments of yawning during fever are lacking. In this study, we determined the effect of experimentally induced fever on yawning frequency. We also explored alternative predictors of yawning during sickness (sleepiness, autonomic nervous system indexes and sickness symptoms). Twenty-two healthy human subjects participated in a randomized, placebo-controlled, cross-over study, where the subjects received an injection of the bacterial endotoxin lipopolysaccharide (LPS) at a dose of 2ng/kg body weight in one condition and placebo in the other. Yawning was scored from video recordings from 30min before to 4h after the injection. Body temperature was measured frequently, alongside with heart rate, blood pressure, nausea and overall sickness symptoms. Yawning frequency was found to significantly increase over time during experimentally induced sickness, but not in the placebo condition. In particular, yawning frequency was increased during the rising phase of body temperature induced by LPS administration, although no significant correlation was found between body temperature increase and yawning frequency. In addition, exploratory analyses showed that a higher yawning frequency was associated with less increase in sickness symptoms and nausea intensity. While the current study adds to previous research showing significant increase in yawning frequency during hyperthermia, further studies are needed if we are to properly characterize the brain cooling role of yawning in humans. The investigation of other functions, such as being a vasovagal inhibitory, may shed stronger light on the functions of yawning.

Central and peripheral activity of cholinesterase inhibitors as revealed by yawning and fasciculation in rats

This study was designed to investigate the central and peripheral activity profile of cholinesterase inhibitors in rats. Intravenous injection of cholinesterase inhibitors caused fasciculation, a fine involuntary muscular movement. This peripheral cholinergic sign was tightly correlated with in vitro anti-acetylcholinesterase activity by cholinesterase inhibitors, suggesting that fasciculation is a valid index of peripheral cholinergic activation. Yawning, used as a marker of central cholinergic activation, was also monitored. E2030 (3-(2-(1-(1,3-dioxolan-2-ylmethyl)-4-piperidyl)ethyl)-2H-3,4-dihydro-1,3-benzoxazin-2,4-dione hydrochloride) elicited yawning at more than 4 mg/kg, while fasciculation was significantly intensified only at a dose of 16 mg/kg. Donepezil and tacrine induced both yawning and fasciculation at doses greater than 4 mg/kg, whereas physostigmine induced both behaviors at a dose of 8 mg/kg and above. Finally, ipidacrine elicited yawning at a dose of 16 mg/kg and fasciculation at doses greater than 8 mg/kg. Thus, all putative centrally acting cholinesterase inhibitors elicited yawning. TAK-147 (3-[1-(phenylmethyl)-4-piperidinyl]-1-(2,3,4,5-tetrahydro-1H-benzazepin-8-yl)-1-propanone fumarate) did not significantly elicit yawning at doses under 16 mg/kg, but elicited fasciculation at a dose of more than 4 mg/kg. Distigmine, a peripherally acting cholinesterase inhibitor, evoked fasciculations, but not yawning. When mild to moderate fasciculation was evoked, donepezil and E2030 elicited more than nine yawns over 30 min, while the other cholinesterase inhibitors elicited approximately five yawns at most during this period. These results indicated that E2030 and donepezil exhibited the most marked preferential central cholinergic activity, relative to peripheral activity, among cholinesterase inhibitors tested. Scopolamine, a centrally acting antimuscarinic drug, completely inhibited E2030-induced yawning, while peripherally acting methylscopolamine did not. Haloperidol, a dopamine receptor antagonist, partially blocked E2030-induced yawning, but did not block donepezil-induced yawning. These results suggest that central cholinergic and, in part, dopaminergic mechanisms are involved in E2030-induced yawning.

Sphenoidal sinus mucocoele and yawning after radiation treatment for nasopharyngeal carcinoma

The long term complications of radiotherapy in treating patients with nasopharyngeal carcinoma (NPC) are well recognized. Among these, neurological and endocrinological complications are usually considered to be more clinically important. On the other hand, postirradiation sinusitis is often neglected or overlooked because symptoms are usually non-specific or not clinically disturbing. This leads to the under-reporting of this complication. We report the case history of a patient with NPC who developed recurrent and debilitating bouts of yawning attacks 13 years after radiotherapy. The attacks were thought to be due to the compression of the hypothalamus by a large mucocoele in the sphenoidal sinus, which was successfully managed by surgical drainage.

The new muscarinic M1-receptor agonist YM796 evokes yawning and increases oxytocin secretion from the posterior pituitary gland in rats

The present experiments were performed to examine the effects of a new muscarinic M1-receptor agonist, (-)-YM796 ((-)-S-2,8-dimethyl-3-methylene-1-oxa-8-azaspiro[4.5]decane L-tartrate monohydrate), on yawning and oxytocin secretion from the posterior pituitary gland in rats YM796, at doses of 2.5-50 mg/kg (SC), elicited yawning. The yawning response was markedly increased by pretreatment with a beta-adrenoceptor antagonist, pindolol (20 mg/kg, IP), which per se did not elicit yawning. The yawning induced by YM796 (10 mg/kg, SC) in combination with pindolol (20 mg/kg, IP) was inhibited by scopolamine (0.5 mg/kg, SC), a muscarinic receptor antagonist, and pirenzcpine (300 micrograms/ rat, ICV) and EEDQ (N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline) (5 mg/kg, IP), muscarinic M1-receptor antagonists, but not by spiperone (0.5 mg/kg, SC), a dopamine D2-receptor antagonist, 4-DAMP (4-diphenylacetoxy-N-methylpiperidine methiodide) (100 micrograms/rat, ICV), a muscarinic M3-receptor antagonist, and [d(CH2)5, Tyr(Mc)2, Orn8]-vasotocin (100 ng/rat, ICV), an oxytocin receptor antagonist. YM796 at 2.5-50 mg/kg (SC) did not exert an action on prolactin levels but increased oxytocin secretion from the posterior pituitary gland in rats. This augmentation of oxytocin secretion by YM796 was inhibited by scopolamine (0.5 mg/kg, SC) and pirenzepine (3 mg/kg, SC), but not by mecamylamine (1 mg/kg, IP), a nicotinic receptor antagonist. The present findings obtained with YM796 suggest that the muscarinic M2-receptor stimulation participates in causing yawning behavior and oxytocin secretion in rats.

Effects of putative dopamine D3 receptor agonists, 7-OH-DPAT, and quinpirole, on yawning, stereotypy, and body temperature in rats

7-OH-DPAT ((+/-)-2-(dipropylamino)-7-hydroxy-1,2,3,4-tetrahydronaphthalene) was recently identified as a dopamine receptor agonist having a > 100-, 1,000- and > 10,000-fold higher affinity for dopamine D3 than for D2, D4 and D1 receptors, respectively. Quinpirole (LY 171555) has also been reported to have a 113-fold greater affinity for dopamine D3 receptors than for D2 receptors. Therefore, we investigated the effects of these putative dopamine D3 receptor agonists on yawning, stereotypy and rectal temperature in rats (N = 424). 7-OH-DPAT and quinpirole administered subcutaneously (SC) at respective low doses of 10-250 micrograms/kg and 25-500 micrograms/kg elicited yawning behavior. The yawning induced by these agents was blocked by spiperone (0.5 mg/kg, SC) and scopolamine (0.5 mg/kg, SC) but was increased by intraperitoneal (IP) administration of pindolol (20 mg/kg). The yawning was also potentiated after treatment with reserpine. 7-OH-DPAT and quinpirole at respective high doses of 0.25 mg/kg (SC) and 0.5 mg/kg (SC) evoked slight stereotypy such as sniffing and licking, and this effect was enhanced by a selective dopamine D1 receptor agonist, SK&F 38393 (1-phenyl-2,3,4,5,-tetrahydro-(1H)-3-benzazepine-7,8-diol). 7-OH-DPAT (0.5 mg/kg, SC) and quinpirole (0.5 mg/kg, SC) decreased, but SK&F 38393 (10 mg/kg, SC) increased body temperature. However, the hyperthermia induced by SK&F 38393 was interestingly enhanced by 7-OH-DPAT and quinpirole.(ABSTRACT TRUNCATED AT 250 WORDS)

Involvement of beta-adrenoceptors in regulation of the yawning induced by neuropeptides, oxytocin and alpha-melanocyte-stimulating hormone, in rats

The present study was undertaken to investigate whether beta-adrenoceptors are involved in regulation of yawning responses to oxytocin and alpha-melanocyte-stimulating hormone (alpha-MSH) in rats. Oxytocin administered intracerebroventricularly (ICV) at doses of 50 and 100 ng/rat elicited yawning. alpha-MSH (20 micrograms/rat, ICV) elicited not only yawning but also stretching and body shaking. RS-86 (2-ethyl-8-methyl-2,8-diazaspiro-(4,5)-decan-1,3-dion hydrobromide), a putative muscarinic M1 receptor agonist, administered ICV at a lower dose of 100 micrograms/rat and subcutaneously (SC) at doses of 0.25-2.5 mg/kg also elicited yawning. The yawning responses produced by these agents were markedly increased by intraperitoneal (IP) pretreatment with a beta-adrenoceptor antagonist, pindolol (20 mg/kg), which per se did not elicit yawning. The yawning induced by oxytocin (50 ng/rat, ICV) plus pindolol, but not that by alpha-MSH (20 micrograms/rat, ICV) or RS-86 (0.5 mg/kg, SC) plus pindolol, was inhibited by [d(CH2)5,Tyr(Me)2,Orn8]-vasotocin (100 ng/rat, ICV), an oxytocin receptor antagonist. The yawning induced by oxytocin, alpha-MSH, or RS-86 administered in combination with pindolol was inhibited by scopolamine (0.5 mg/kg, SC), a mucarinic receptor antagonist, without being affected by spiperone (0.5 mg/kg, SC), a dopamine D2 receptor antagonist. The results suggest that the yawning produced by the neuropeptides oxytocin and alpha-MSH is modulated by beta-adrenoceptor activity in an inhibitory manner as that produced by muscarinic M1 receptor agonists, and that it involves cholinergic, but not dopaminergic, activation.