Role of calcium in the expression of ACTH-induced stretching, yawning and penile erection

Genotype-dependent effect of ACTH1-24 on grooming and yawning in two inbred strains of rats

It has long been known that the intracerebroventricular administration of ACTH1-24 increases the duration of grooming episodes and the frequency of yawning in rats. The objective of this study was to investigate in what way these episodes are prolonged and whether and to what extent genotype influences such effects. We compared the effect of increasing doses of intracerebroventricular injections of ACTH1-24 on grooming and yawning in males of two inbred strains of Sprague-Dawley rats with distinct yawning frequency, high-yawning (HY) and low-yawning (LY). In LY rats the duration of grooming episodes increased, while in HY rats grooming episodes augmented both in number and duration. In LY rats the duration of grooming components increased likewise, in HY rats however, neither the number nor the duration of the components changed. The grooming rate in both strains of rats was slowed, though more so in LY than in HY rats. Yawning increased in LY rats but not in HY rats. We conclude therefore that ACTH1-24 increases the duration of grooming episodes by slowing the grooming rate according to genotype, and may or may not alter the frequency of yawning.

Adrenalectomy and dexamethasone replacement on yawning behavior

Yawning, a phylogenetic behavior, present in reptiles, birds and mammals, has been studied for several decades, but to date its physiological function is still unknown. The role of stress as well as several peptides and the hypothalamus has been studied in relation to its regulation. To date however, no studies has been carried out to determine the role of the adrenal glands. Therefore, yawning behavior was studied in adrenalectomized rats, who then received dexamethasone replacement. The results show that rats whose adrenal glands were removed stopped both spontaneous and apomorphine-induced yawning, while dexamethasone reverted this effect. The results are discussed in terms of the possible role of corticosterone on yawning behavior.

ACTH- and alpha-MSH-induced grooming, stretching, yawning and penile erection in male rats: site of action in the brain and role of melanocortin receptors

The effect of adrenocorticotropin (ACTH)(1-24) and alpha-melanocyte stimulating hormone (alpha-MSH) on grooming, stretching, yawning and penile erection was studied after injection into different brain areas. Both peptides induce the above responses when injected into the hypothalamic periventricular region of the third ventricle. This region includes the paraventricular nucleus, the dorsomedial nucleus, the ventromedial nucleus and the anterior hypothalamic area. The minimal effective dose of both peptides was 0.5 microg and the maximal effect was seen with 2 microg, the highest dose tested. Irrespective of the injection site, grooming started 5-7 min after injection of either peptide, while stretching, yawning and penile erection started only after 15-35 min and lasted for 90-120 min. In contrast both peptides were ineffective when injected into the preoptic area, the caudate nucleus or the CA1 field of the hippocampus. Grooming, stretching and yawning, but not penile erection, were prevented by cyclic[AcCys(11), D-Nal(14), Cys(18), AspNH(2)(22)]-beta-MSH (11-22) (HS014), a selective melanocortin 4 receptor antagonist, injected into the same periventricular area 10 min before of ACTH(1-24) or alpha-MSH. The results show that ACTH(1-24) and alpha-MSH act in the hypothalamic periventricular region to induce the above responses and that grooming, stretching and yawning, but not penile erection, are mediated by melanocortin 4 receptors.

Investigation of stretching behaviour induced by the selective 5-HT6 receptor antagonist, Ro 04-6790, in rats

1. The present study examined the effects of the selective 5-HT6 receptor antagonist 4-amino-N-(2, 6 bis-methylamino-pyrimidin-4-yl)-benzene sulphonamide (Ro 04-6790) on locomotor activity and unconditioned behaviour in male Sprague Dawley rats (230-300 g). 2. In non-quantified behavioural observations, animals treated with Ro 04-6790 (3, 10 or 30 mg kg(-1), i.p) showed no overt behavioural signs except a dose-dependent reduction in locomotor activity and a behavioural syndrome of stretching, yawning and chewing. The latter behaviour was most pronounced between 30 and 90 min following the administration of Ro 04-6790. 3. Detailed analysis of the stretching and yawning behaviour showed that Ro 04-6790 (3, 10 or 30 mg kg(-1), i.p.) dose-dependently induced stretching. The number of stretches observed following treatment with either Ro 04-6790 (10 mg kg(-1) i.p.) or Ro-04-6790 (30 mg kg(-1), i.p.) was significantly greater than that observed in saline-treated rats. The yawning behaviour, however, was not dose-dependent nor was the number of yawns in any of the drug treated groups significantly greater than in those treated with saline. 4. Pretreatment (30 min) with the non-selective muscarinic antagonists scopolamine (0.1, 0.3 or 1 mg kg(-1), i.p.) and atropine (0.3, 1 or 3 mg kg(-1), s.c.) but not methylatropine (1, 3 or 10 mg kg(-1), s.c) significantly inhibited stretching induced by Ro 04-6790 (30 mg kg(-1), i.p.). 5. The dopamine D2-like receptor antagonist, haloperidol (0.03, 0.1 or 0.3 mg kg(-1), s.c.) given at the same time as Ro 04-6790 (30 mg kg(-1), i.p.) had no effect on the stretching induced by the 5-HT6 antagonist. 6. These data suggest that systemic injection of the 5-HT6 antagonist, Ro 04-6790, produces a stretching behaviour that appears to be mediated by an increase in cholinergic neurotransmission in the CNS and which could be a useful functional correlate for 5-HT6 receptor blockade. There is no evidence for dopamine D2-like receptor involvement in this behaviour.

The neuropharmacology of yawning

Yawning is a phylogenetically old, stereotyped event that occurs alone or associated with stretching and/or penile erection in humans and in animals from reptiles to birds and mammals under different conditions. Although its physiological function is still unknown, yawning is under the control of several neurotransmitters and neuropeptides at the central level as this short overview of the literature on the neurochemistry of yawning shows. Among these substances, the best known are dopamine, excitatory amino acids, acetylcholine, serotonin, nitric oxide, adrenocorticotropic hormone-related peptides and oxytocin, that facilitate yawning and opioid peptides that inhibit this behavioral response. Some of the above compounds interact in the paraventricular nucleus of the hypothalamus to control yawning. This hypothalamic nucleus contains the cell bodies of oxytocinergic neurons projecting to extra-hypothalamic brain areas that play a key role in the expression of this behavioral event. When activated by dopamine, excitatory amino acids and oxytocin itself, these neurons facilitate yawning by releasing oxytocin at sites distant form the paraventricular nucleus, i.e. the hippocampus, the pons and/or the medulla oblongata. Conversely, activation of these neurons by dopamine, oxytocin or excitatory amino acids, is antagonized by opioid peptides, that, in turn, prevent the yawning response. The activation and inhibition, respectively of these oxytocinergic neurons is related to a concomitant increase and decrease, respectively, of paraventricular nitric oxide synthase activity. However, other neuronal systems in addition to the central paraventricular oxytocinergic neurons are involved in the control of yawning, since they do not seem to be involved in the expression of yawning induced by the stimulation of acetylcholine or serotoninergic receptors, nor by adrenocorticotropic hormone (ACTH) and related peptides. Nitric oxide is also involved in the induction of yawning by the latter compounds and neuronal links, for instance between dopamine and acetylcholine and dopamine and serotonin, seem to be involved in the yawning response. Finally, other neurotransmitters, i.e. gamma-aminobutyric acid (GABA) and noradrenaline, and neuropeptides, i.e. neurotensin and luteinizing hormone-releasing hormone (LH-RH), influence this behavioral response. In conclusion, in spite of some recent progress, little is known of, and more has to be done to identify, the neurochemical mechanisms underlying yawning at the central level.

Role of central nitric oxide in the control of penile erection and yawning

1. Recent experimental evidence has shown that nitric oxide (NO) plays an important role in the expression of penile erection and yawning and that this molecule has to be added to the list of the best known neurotransmitters and neuropeptides involved in this symptomatology. 2. This was first suggested by the ability of NO synthase inhibitors injected in the lateral ventricles (i.c.v.) or in the paraventricular nucleus of the hypothalamus (PVN) to prevent these behavioral responses induced by dopamine agonists, oxytocin and NMDA. The inhibitory effect of NO synthase inhibitors was not observed when these compounds were injected concomitantly with L-arginine, the precursor of NO. Most important, this hypothalamic nucleus is one of the richest brain areas of NO synthase and also the brain site where dopamine, NMDA and oxytocin act to induce penile erection and yawning by activating central NO synthase containing oxytocinergic neurons. 3. NO synthase inhibitors given i.c.v. but not in the PVN prevent also penile erection and yawning induced by ACTH and serotonin1c agonists, which induce these responses by acting with mechanisms unrelated to oxytocinergic transmission. 4. Dopamine agonists, NMDA and oxytocin increase NO production in the PVN at doses that induce penile erection and yawning, as determined by measuring the concentration of NO2- and NO3- in the dialyzate obtained with a vertical probe implanted in the PVN by in vivo microdialysis. 5. NO donors, such as nitroglycerin, sodium nitroprusside and hydroxylamine, induce penile erection and yawning indistinguishable from those induced by oxytocin, dopamine agonists or NMDA when injected in the PVN. The NO donor response was prevented by the i.c.v. injection of the oxytocin receptor antagonist d(CH2)5-Tyr(Me)-Orn8-vasotocin, indicating that these compounds also induce penile erection and yawning by activating oxytocinergic transmission. 6. Finally, guanylate cyclase inhibitors (i.e. methylene blue and LY 83583) and hemoglobin injected in the PVN do not prevent drug-induced penile erection and yawning, nor 8-Br-cGMP injected in the PVN induces these behavioral responses suggesting that the mechanism by means of which endogenous or NO donor-derived NO facilitates oxytocinergic transmission to induce penile erection and yawning is not related to the activation of guanylate cyclase. Furthermore, since hemoglobin, in spite of its ability to prevent drug-induced NO production in the PVN, does not prevent penile erection and yawning, it is likely that NO acts as an intracellular rather than an intercellular modulator in the PVN neurons in which is formed to facilitate the expression of these behavioral responses.

Nitric oxide donors induce penile erection and yawning when injected in the central nervous system of male rats

In order to provide further support for a role of central nitric oxide as a mediator of penile erection and yawning, the nitric oxide donors sodium nitroprusside, hydroxylamine, isoamyl nitrite and S-nitroso-N-acetyl-penicillamine were injected into the lateral ventricles (i.c.v.) or into the paraventricular nucleus of the hypothalamus of male rats. Of the above compounds injected i.c.v., only isoamyl nitrite (10-100 micrograms) induced penile erection and yawning, while the others induced dramatic behavioral changes, such as motor hyperactivity and convulsions, that masked the above responses. Nevertheless, nitric oxide donors in doses ranging from 10 to 50 micrograms, for except S-nitroso-N-acetyl-penicillamine that was injected only at the dose of 10 micrograms and isoamyl nitrite that was not injected at all because of poor solubility, induced penile erection and yawning when injected in the paraventricular nucleus. Nitric oxide donor-induced responses were prevented by methylene blue and LY 83583, inhibitors of guanylate cyclase, the best known target of nitric oxide, given i.c.v. but not in the paraventricular nucleus. However, 8-bromo-guanosine 3':5'-cyclic monophosphate (8-Br-cGMP), a stable cGMP analog, and hemoglobin, a nitric oxide scavenger, were ineffective in inducing and preventing, respectively, penile erection and yawning when injected either i.c.v. or in the paraventricular nucleus. Nitric oxide donor-induced responses were also prevented by the nonapeptide oxytocin receptor antagonist d(CH2)5-Tyr(Me)-Orn8-vasotocin given i.c.v. but not in the paraventricular nucleus. The present results suggest that nitric oxide donors induce penile erection and yawning by activating central oxytocinergic transmission in the paraventricular nucleus of the hypothalamus via a cGMP-independent mechanism.

Nitric oxide is a central mediator of penile erection

In order to evaluate a possible role of brain nitric oxide (NO) on the control of penile erection, the effect of nitroglycerin, that is thought to act by producing NO, was studied on spontaneous penile erection in male rats. In addition the effect of drugs that prevent NO formation and/or activity such as NG-nitro-L-arginine methyl ester (NAME) and methylene blue, on N-methyl-D-aspartic acid (NMDA)-, apomorphine- and oxytocin-induced penile erection was also studied. Nitroglycerin induced penile erection in a dose-dependent manner when given intracerebroventricularly (i.c.v.) (33-99 micrograms) or in the paraventricular nucleus of the hypothalamus (0.8-3.3 micrograms). Nitroglycerin-induced penile erection was prevented by the guanylate cyclase inhibitor methylene blue injected i.c.v. (200-400 micrograms) but not in the paraventricular nucleus of the hypothalamus (10-20 micrograms). Conversely, NMDA-, apomorphine- and oxytocin-induced penile erection was prevented by NAME (150 micrograms) or methylene blue (400 micrograms) given i.c.v. NAME (20 micrograms), but not methylene blue (20 micrograms), was effective in preventing the behavioral response also when injected in the paraventricular nucleus. The present results suggest that NO is a common mediator of several neurotransmitters involved in the control of this primary male sexual function.

Penile erection and yawning induced by 5-HT1C receptor agonists in male rats: relationship with dopaminergic and oxytocinergic transmission

1-(3-Chlorophenyl)piperazine (m-CPP) (0.1-4 mg/kg s.c.) and N-(3-trifluoromethylphenyl)-piperazine (TFMPP) (0.5-4 mg/kg s.c.), 5-HT1C receptor agonists, but not 8-hydroxy-dipropylamino-tetralin (8-OH-DPAT) (0.1 and 0.2 mg/kg s.c.), a 5-HT1A receptor agonist, induced penile erection and yawning with a U-inverted dose-response curve in male rats. The maximal effect was found with 0.5 mg/kg s.c. of m-CPP and with 1 mg/kg s.c. of TFMPP. The m-CPP (0.5 mg/kg s.c.) and TFMPP (1 mg/kg s.c.) responses were prevented by mianserin (0.2 mg/kg s.c.) and by ritanserin (1 mg/kg s.c.) given 15 min before m-CPP and TFMPP. In contrast, m-CPP- or TFMPP-induced penile erection and yawning were not antagonized by haloperidol (0.1 mg/kg s.c.) or by [d(CH2)5Tyr(Me)2,Orn8]vasotocin (5 micrograms i.c.v.). Apomorphine- and oxytocin-induced penile erection, but not yawning, was also antagonized by mianserin and less effectively by ritanserin. The results suggest that 5-HT1C receptor agonist-induced penile erection and yawning are not mediated by increased dopaminergic and/or oxytocinergic transmission, and raise the possibility that a neuronal dopamine-oxytocin-5-HT link is involved in the control of penile erection and not necessarily of yawning in male rats.

Penile erection and yawning induced by paraventricular NMDA injection in male rats are mediated by oxytocin

The effect of N-methyl-D-aspartic acid (NMDA), (+-)-alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA), or (+-)-trans-1-amino-1,3-cyclo-pentanedicarboxylic acid (ACPD) (5-60 ng in 0.3 microliter of saline) microinjected in the paraventricular nucleus of the hypothalamus on penile erection and yawning was studied in male rats. NMDA induced both penile erection and yawning in a dose-dependent manner. AMPA and ACPD also induced penile erection but less potently than NMDA, but were ineffective in causing yawning. NMDA effect on penile erection and yawning was prevented by (+)-MK-801 (0.05-0.1 mg/kg IP, 10 min before NMDA), by the oxytocin antagonist d(CH2)5Tyr(Me)-Orn8- vasotocin (50-100 ng ICV 10 min before NMDA), but not by haloperidol (0.1-0.5 mg/kg IP 10 min before NMDA). The results suggest that NMDA induces penile erection and yawning by increasing oxytocinergic transmission by acting in the paraventricular nucleus of the hypothalamus.

Role of neuronal and vascular Ca(2+)-channels in the ACTH-induced reversal of haemorrhagic shock

1. In a rat model of volume-controlled haemorrhagic shock causing the death of all control (saline-treated) animals within 30 min, the intravenous (i.v.) bolus injection of ACTH-(1-24) at a dose of 160 micrograms kg-1 produced an impressive and sustained restoration of arterial pressure, pulse pressure and respiratory function, with 100% survival at the end of the observation period (2 h). 2. Both intracerebroventricular (i.c.v., 0.015-0.06 microgram kg-1) and i.v. (5 micrograms kg-1) pretreatment with the N-calcium channel blocker, omega-conotoxin GVIA, and i.v. (but not i.c.v.) pretreatment with the L-calcium channel blocker, nicardipine (125-500 micrograms kg-1) dose-dependently prevented the ACTH-induced shock reversal. 3. These results further indicate that the effect of ACTH in haemorrhagic shock may involve a neuronal link and the eventual restoration of vascular tone mediated by N- and L-type calcium channels, respectively.

Effect of excitatory amino acid receptor antagonists on apomorphine-, oxytocin- and ACTH-induced penile erection and yawning in male rats

The effect of excitatory amino acid receptor antagonists, (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclo-hepten-5, 10-imine hydrogen maleate ((+)-MK-801), (+/-)-3-(2-carboxy-piperazin-4-yl)-propyl-1-phosphonic acid (CPP), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and (+/-)-2-amino-4-phosphonobutanoic acid (AP-4), on penile erection and yawning induced by subcutaneous apomorphine (80 micrograms/kg), intracerebroventricular (i.c.v.) oxytocin (30 ng) and adrenocorticotropin (ACTH)-(1-24) (10 micrograms) was studied in male rats. Intraperitoneal (0.1-0.4 mg/kg) and i.c.v. (10-50 micrograms) (+)-MK-801 prevented dose dependently the penile erection and yawning induced by the three drugs. The (+)-MK-801 effect coincided with the appearance of head weaving, body rolling, hyperlocomotion and ataxia. Haloperidol (0.5 mg/kg i.p.) antagonized the prevention by (+)-MK-801 of oxytocin responses. Penile erection but not yawning was also prevented by high, but not low doses of CPP and CNQX, which impaired motor performance, AP-4 was ineffective at all doses tested. The above compounds were ineffective when injected into the paraventricular nucleus of the hypothalamus, the brain area where apomorphine and oxytocin act to induce penile erection and yawning. The results suggest that excitatory amino acid transmission is not involved in the expression of penile erection and yawning induced by the above compounds.