sb-334867-a and Tobacco-Use-Disorder

Hypocretin (orexin) signaling is involved in drug addiction. In this study, we investigated the role of these hypothalamic neuropeptides in nicotine withdrawal by using behavioral and neuroanatomical approaches.. Nicotine withdrawal syndrome was precipitated by mecamylamine (2 mg/kg, subcutaneous) in C57BL/6J nicotine-dependent mice (25 mg/kg/day for 14 days) pretreated with the hypocretin receptor 1 (Hcrtr-1) antagonist SB334867 (5 and 10 mg/kg, intraperitoneal), the hypocretin receptor 2 antagonist TCSOX229 (5 and 10 mg/kg, intraperitoneal), and in preprohypocretin knockout mice. c-Fos expression was analyzed in several brain areas related to nicotine dependence by immunofluorescence techniques. Retrograde tracing with rhodamine-labeled fluorescent latex microspheres was used to determine whether the hypocretin neurons project directly to the paraventricular nucleus of the hypothalamus (PVN), and SB334867 was locally administered intra-PVN (10 nmol/side) to test the specific involvement of Hcrtr-1 in this brain area during nicotine withdrawal.. Somatic signs of nicotine withdrawal were attenuated in mice pretreated with SB334867 and in preprohypocretin knockout mice. No changes were found in TCSOX229 pretreated animals. Nicotine withdrawal increased the percentage of hypocretin cells expressing c-Fos in the perifornical, dorsomedial, and lateral hypothalamus. In addition, the increased c-Fos expression in the PVN during withdrawal was dependent on hypocretin transmission through Hcrtr-1 activation. Hypocretin neurons directly innervate the PVN and the local infusion of SB334867 into the PVN decreased the expression of nicotine withdrawal.. These data demonstrate that hypocretin signaling acting on Hcrtr-1 in the PVN plays a crucial role in the expression of nicotine withdrawal.

Topics: Animals; Antigens, Surface; Benzoxazoles; Intracellular Signaling Peptides and Proteins; Isoquinolines; Male; Mecamylamine; Mice; Mice, Inbred C57BL; Mice, Knockout; Microinjections; Molecular Imaging; Naphthyridines; Neuroanatomical Tract-Tracing Techniques; Neuropeptides; Orexin Receptors; Orexins; Paraventricular Hypothalamic Nucleus; Pyridines; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Receptors, Neuropeptide; Substance Withdrawal Syndrome; Tobacco Use Disorder; Urea

Emerging evidence suggests that the hypocretinergic system is involved in addictive behavior. In this study, we investigated the role of these hypothalamic neuropeptides in anxiety-like responses of nicotine and stress-induced reinstatement of nicotine-seeking behavior. Acute nicotine (0.8 mg/kg, s.c.) induced anxiogenic-like effects in the elevated plus-maze and activated the paraventricular nucleus of the hypothalamus (PVN) as revealed by c-Fos expression. Pretreatment with the hypocretin receptor 1 (Hcrtr-1) antagonist SB334867 or preprohypocretin gene deletion blocked both nicotine effects. In the PVN, SB334867 also prevented the activation of corticotrophin releasing factor (CRF) and arginine-vasopressin (AVP) neurons, which expressed Hcrtr-1. In addition, an increase of the percentage of c-Fos-positive hypocretin cells in the perifornical and dorsomedial hypothalamic (PFA/DMH) areas was found after nicotine (0.8 mg/kg, s.c.) administration. Intracerebroventricular infusion of hypocretin-1 (Hcrt-1) (0.75 nmol/1 mul) or footshock stress reinstated a previously extinguished nicotine-seeking behavior. The effects of Hcrt-1 were blocked by SB334867, but not by the CRF1 receptor antagonist antalarmin. Moreover, SB334867 did not block CRF-dependent footshock-induced reinstatement of nicotine-seeking while antalarmin was effective in preventing this nicotine motivational response. Therefore, the Hcrt system interacts with CRF and AVP neurons in the PVN and modulates the anxiogenic-like effects of nicotine whereas Hcrt and CRF play a different role in the reinstatement of nicotine-seeking. Indeed, Hcrt-1 reinstates nicotine-seeking through a mechanism independent of CRF activation whereas CRF mediates the reinstatement induced by stress.

Topics: Animals; Anxiety; Arginine Vasopressin; Behavior, Addictive; Benzoxazoles; Conditioning, Operant; Corticotropin-Releasing Hormone; Extinction, Psychological; Intracellular Signaling Peptides and Proteins; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Naphthyridines; Neurons; Neuropeptides; Nicotine; Orexin Receptors; Orexins; Paraventricular Hypothalamic Nucleus; Pyrimidines; Pyrroles; Receptors, Corticotropin-Releasing Hormone; Receptors, G-Protein-Coupled; Receptors, Neuropeptide; Self Administration; Tobacco Use Disorder; Urea

Damage to the insular cortex can profoundly disrupt tobacco addiction in human smokers, reflected in spontaneous cessation of the tobacco habit and persistently decreased urge to smoke. Little is known concerning the neurobiological mechanisms through which the insula may control the maintenance of the tobacco habit. Emerging evidence suggests that hypocretin (orexin) transmission may play an important role in drug reinforcement processes, but its role in the rewarding actions of nicotine, considered the key addictive component of tobacco smoke, remains largely unexplored. Here we show that blockade of hypocretin transmission at hypocretin-1 (Hcrt-1; orexin-1) receptors decreases i.v. nicotine self-administration in rats and the motivation to obtain the drug. Blockade of Hcrt-1 receptors also abolished the stimulatory effects of nicotine on brain reward circuitries, as measured by reversal of nicotine-induced lowering of intracranial self-stimulation thresholds. In addition, we show that hypocretin-containing fibers innervate the insula, Hcrt-1 receptors are located on insular cells, and blockade of Hcrt-1 receptors in the insula but not in the adjacent somatosensory cortex decreases nicotine self-administration. These data demonstrate that insular hypocretin transmission plays a permissive role in the motivational properties of nicotine, and therefore may be a key neurobiological substrate necessary for maintaining tobacco addiction in human smokers.

Topics: Animals; Benzoxazoles; Cerebral Cortex; Intracellular Signaling Peptides and Proteins; Male; Motivation; Naphthyridines; Neuropeptides; Nicotine; Nicotinic Agonists; Orexin Receptors; Orexins; Rats; Rats, Wistar; Receptors, G-Protein-Coupled; Receptors, Neuropeptide; Reward; Self Administration; Smoking; Synaptic Transmission; Tobacco Use Disorder; Urea