Direct and indirect nigrofugal projections to the nucleus reticularis pontis caudalis mediate in the motor execution of the acoustic startle reflex.

The acoustic startle reflex (ASR) is a short and intense defensive reaction in response to a loud and unexpected acoustic stimulus. In the rat, a primary startle pathway encompasses three serially connected central structures: the cochlear root neurons, the giant neurons of the nucleus reticularis pontis caudalis (PnC), and the spinal motoneurons. As a sensorimotor interface, the PnC has a central role in the ASR circuitry, especially the integration of different sensory stimuli and brain states into initiation of motor responses. Since the basal ganglia circuits control movement and action selection, we hypothesize that their output via the substantia nigra (SN) may interplay with the ASR primary circuit by providing inputs to PnC. Moreover, the pedunculopontine tegmental nucleus (PPTg) has been proposed as a functional and neural extension of the SN, so it is another goal of this study to describe possible anatomical connections from the PPTg to PnC. Here, we made 6-OHDA neurotoxic lesions of the SN pars compacta (SNc) and submitted the rats to a custom-built ASR measurement session to assess amplitude and latency of motor responses. We found that following lesion of the SNc, ASR amplitude decreased and latency increased compared to those values from the sham-surgery and control groups. The number of dopamine neurons remaining in the SNc after lesion was also estimated using a stereological approach, and it correlated with our behavioral results. Moreover, we employed neural tract-tracing techniques to highlight direct projections from the SN to PnC, and indirect projections through the PPTg. Finally, we also measured levels of excitatory amino acid neurotransmitters in the PnC following lesion of the SN, and found that they change following an ipsi/contralateral pattern. Taken together, our results identify nigrofugal efferents onto the primary ASR circuit that may modulate motor responses.

Idosos residentes em uma instituição de longa permanência: adaptação à luz de Callista Roy / Elderly residents in homes for the aged: adjustment in the light of Callista Roy / Residentes mayores en un hogares para ancianos: adaptación a la luz de Callista Roy

Objetivou-se avaliar o processo de adaptação de idosos que buscam, voluntariamente, residir em Instituição de Longa Permanência para Idosos (ILPI), na cidade de Fortaleza-CE, com base no modelo teórico de Roy. Pesquisa descritiva, realizada em uma IPLI com treze idosos residentes. A coleta de dados foi por meio de entrevista, nos meses de outubro e dezembro de 2011. Os dados foram tratados pela análise de conteúdo temática. Emergiram as seguintes temáticas: Eu Físico, subdividido em sensação corporal e imagem corporal; e Eu Pessoal, subdividido em auto coerência, auto ideal e ser moral-ético-espiritual. Assim, a opção de morar em ILPI não mudou efetivamente a vida dos idosos. Estes conseguiram adaptação ao local e convivem bem com os estímulos internos e externos.

This study aimed to evaluate the adaptation of elderly individuals voluntarily reside in Institution for the Aged (LTCF) in the city of Fortaleza-CE, based on the theoretical model of Roy. Descriptive study, in a IPLI involving thirteen elderly residents. Data collect was through interviews in the months of October and December 2011 and organized by thematic content analysis. The following themes has emerged: I Physical subdivided into body sensation and body image; Staff and I, subdivided into self-consistency and auto ideal be moral-ethical-spiritual. Thus, the option to live in ILPI not effectively changed the lives of elderly people. They managed to adapt to the local and coexist well with internal and external stimuli.

Este estudio tuvo como objetivo evaluar la adaptación de las personas mayores que residen voluntariamente en la Institución para la tercera edad (LTCF) en la ciudad de Fortaleza-CE, basado en el modelo teórico de Roy. Estudio descriptivo, en un IPLI con trece ancianos residentes. Los datos fueran recogidos a través de entrevistas en los meses de octubre y diciembre de 2011 y organizados mediante análisis de contenido temático. Emergieron los siguientes temas: subdivide I Física en la imagen corporal y sensación de cuerpo; El personal y yo, subdividen en auto-consistencia y auto ideal ser moral-ético-espiritual. Por lo tanto, la opción de vivir en ILPI no cambió de manera efectiva la vida de los ancianos. Se las arreglaron para adaptarse a lo local y convivir bien con los estímulos internos y externos.

Intrinsic connections within the pedunculopontine tegmental nucleus are critical to the elaboration of post-ictal antinociception.

This study investigated the intrinsic connections of a key-structure of the endogenous pain inhibitory system, the pedunculopontine tegmental nucleus (PPTN), in post-ictal antinociceptive process through synaptic inactivation of the PPTN with cobalt chloride. Male Wistar rats (n = 6 or 7 per group), weighing 250-280 g, had the tail-flick baseline recorded and were submitted to a stereotaxic surgery for the introduction of a guide-cannula aiming at the PPTN. After 5 days of postoperative recovery, cobalt chloride (1 mM/0.2 µL) or physiological saline (0.2 µL) were microinjected into the PPTN and after 5 min, the tail-withdrawal latency was measured again at 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, and 120 min after seizures evoked by intraperitoneal injection of pentylenetetrazole (64 mg/kg). The synaptic inactivation of PPTN decreased the post-ictal antinociceptive phenomenon, suggesting the involvement of PPTN intrinsic connections in the modulation of pain, during tonic-clonic seizures. These results showed that the PPTN may be crucially involved in the neural network that organizes the post-ictal analgesia.

Role of glutamate receptors in the dorsal reticular nucleus in formalin-induced secondary allodynia.

The role of glutamate receptors present in the medullary dorsal reticular nucleus (DRt) in the formalin test and formalin-induced secondary nociception was studied in rats. Secondary mechanical allodynia was assessed with von Frey filaments applied to the rat's hindpaw, and secondary thermal hyperalgesia was evaluated with the tail-immersion test. The selective glutamate receptor antagonists MK801 (N-methyl-D-aspartate receptor antagonist), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (AMPA/KA receptor antagonist) and A841720 (metabotropic glutamate 1 receptor antagonist) were injected into the DRt before or 6 days after formalin injection in the rat. In the formalin test, the three antagonists significantly reduced the number of flinches in both phases of the test. DRt microinjection of MK801 or A841720, but not of CNQX, reduced both secondary nociceptive behaviors. Moreover, pre-treatment with the three antagonists injected into the DRt prevented the development of secondary mechanical allodynia and secondary thermal hyperalgesia. Similarly, in these rats, the number of c-Fos-like immunoreactive neurons were markedly reduced in both the superficial and deep lamina of the dorsal horn. Our findings support the role of DRt as a pain facilitator in acute and chronic pain states, and suggest a key role of glutamate receptors during the development and maintenance of formalin-induced secondary allodynia.

Adenosine A(1) receptors in mouse pontine reticular formation depress breathing, increase anesthesia recovery time, and decrease acetylcholine release.

BACKGROUND: Clinical and preclinical data demonstrate the analgesic actions of adenosine. Central administration of adenosine agonists, however, suppresses arousal and breathing by poorly understood mechanisms. This study tested the two-tailed hypothesis that adenosine A1 receptors in the pontine reticular formation (PRF) of C57BL/6J mice modulate breathing, behavioral arousal, and PRF acetylcholine release. METHODS: Three sets of experiments used 51 mice. First, breathing was measured by plethysmography after PRF microinjection of the adenosine A1 receptor agonist N-sulfophenyl adenosine (SPA) or saline. Second, mice were anesthetized with isoflurane and the time to recovery of righting response (RoRR) was quantified after a PRF microinjection of SPA or saline. Third, acetylcholine release in the PRF was measured before and during microdialysis delivery of SPA, the adenosine A1 receptor antagonist 1, 3-dipropyl-8-cyclopentylxanthine, or SPA and 1, 3-dipropyl-8-cyclopentylxanthine. RESULTS: First, SPA significantly decreased respiratory rate (-18%), tidal volume (-12%), and minute ventilation (-16%). Second, SPA concentration accounted for 76% of the variance in RoRR. Third, SPA concentration accounted for a significant amount of the variance in acetylcholine release (52%), RoRR (98%), and breathing rate (86%). 1, 3-dipropyl-8-cyclopentylxanthine alone caused a concentration-dependent increase in acetylcholine, a decrease in RoRR, and a decrease in breathing rate. Coadministration of SPA and 1, 3-dipropyl-8-cyclopentylxanthine blocked the SPA-induced decrease in acetylcholine and increase in RoRR. CONCLUSIONS: Endogenous adenosine acting at adenosine A1 receptors in the PRF modulates breathing, behavioral arousal, and acetylcholine release. The results support the interpretation that an adenosinergic-cholinergic interaction within the PRF comprises one neurochemical mechanism underlying the wakefulness stimulus for breathing.

[Effect of the Na+, K(+)-ATPase modulation in neurons of the medulla oblongata on hemodynamic effects in spontaneously hypertensive rats].

The study was conducted in normotensive and spontaneously hypertensive rats anesthetized with urethane (1600 mg/kg of animal weight, intraperitoneally). It has been shown that in normotensive rats, injections of a specific inhibitor of Na+, K(+)-ATPase ouabain (10(-8)-10(-5) mol/l) in the populations of the neurons within nucleus of the solitary tract (NTS), paramedian reticular nucleus (PMn) and lateral reticular nucleus (LRN) were accompanied by the development of the hypertensive responses in a dose-dependent fashion. These data suggest that Na+, K(+)-ATPase of the neuron somatic membranes in the medullary cardiovascular nuclei is involved in neural control of the cardiovascular function, and its inhibition by microinjections of ouabain promotes the development of hypertension. In contrast to normotensive rats, ouabain injected in the medullary nuclei of spontaneously hypertensive animals induced either enhanced hypertensive or hypotensive responses. Biochemical analysis revealed that the activity of Na+, K(+)-ATPase in the microsomal fraction of the medulla oblongata of spontaneously hypertensive rats significantly exceeded its activity in the medulla oblongata of normotensive animals. Possible mechanisms of ouabain effects in spontaneously hypertensive rats have being discussed. Activation of Na+, K(+)-ATPase activity of the cardiovascular neurons with asparkam injections in the medullary nuclei resulted in hypotensive responses in both normotensive and spontaneously hypertensive rats.

A trigeminoreticular pathway: implications in pain.

Neurons in the caudalmost ventrolateral medulla (cmVLM) respond to noxious stimulation. We previously have shown most efferent projections from this locus project to areas implicated either in the processing or modulation of pain. Here we show the cmVLM of the rat receives projections from superficial laminae of the medullary dorsal horn (MDH) and has neurons activated with capsaicin injections into the temporalis muscle. Injections of either biotinylated dextran amine (BDA) into the MDH or fluorogold (FG)/fluorescent microbeads into the cmVLM showed projections from lamina I and II of the MDH to the cmVLM. Morphometric analysis showed the retrogradely-labeled neurons were small (area 88.7 µm(2)±3.4) and mostly fusiform in shape. Injections (20-50 µl) of 0.5% capsaicin into the temporalis muscle and subsequent immunohistochemistry for c-Fos showed nuclei labeled in the dorsomedial trigeminocervical complex (TCC), the cmVLM, the lateral medulla, and the internal lateral subnucleus of the parabrachial complex (PBil). Additional labeling with c-Fos was seen in the subnucleus interpolaris of the spinal trigeminal nucleus, the rostral ventrolateral medulla, the superior salivatory nucleus, the rostral ventromedial medulla, and the A1, A5, A7 and subcoeruleus catecholamine areas. Injections of FG into the PBil produced robust label in the lateral medulla and cmVLM while injections of BDA into the lateral medulla showed projections to the PBil. Immunohistochemical experiments to antibodies against substance P, the substance P receptor (NK1), calcitonin gene regulating peptide, leucine enkephalin, VRL1 (TPRV2) receptors and neuropeptide Y showed that these peptides/receptors densely stained the cmVLM. We suggest the MDH- cmVLM projection is important for pain from head and neck areas. We offer a potential new pathway for regulating deep pain via the neurons of the TCC, the cmVLM, the lateral medulla, and the PBil and propose these areas compose a trigeminoreticular pathway, possibly the trigeminal homologue of the spinoreticulothalamic pathway.

Buprenorphine disrupts sleep and decreases adenosine concentrations in sleep-regulating brain regions of Sprague Dawley rat.

BACKGROUND: Buprenorphine, a partial µ-opioid receptor agonist and κ-opioid receptor antagonist, is an effective analgesic. The effects of buprenorphine on sleep have not been well characterized. This study tested the hypothesis that an antinociceptive dose of buprenorphine decreases sleep and decreases adenosine concentrations in regions of the basal forebrain and pontine brainstem that regulate sleep. METHODS: Male Sprague Dawley rats were implanted with intravenous catheters and electrodes for recording states of wakefulness and sleep. Buprenorphine (1 mg/kg) was administered systemically via an indwelling catheter and sleep-wake states were recorded for 24 h. In additional rats, buprenorphine was delivered by microdialysis to the pontine reticular formation and substantia innominata of the basal forebrain while adenosine was simultaneously measured. RESULTS: An antinociceptive dose of buprenorphine caused a significant increase in wakefulness (25.2%) and a decrease in nonrapid eye movement sleep (-22.1%) and rapid eye movement sleep (-3.1%). Buprenorphine also increased electroencephalographic delta power during nonrapid eye movement sleep. Coadministration of the sedative-hypnotic eszopiclone diminished the buprenorphine-induced decrease in sleep. Dialysis delivery of buprenorphine significantly decreased adenosine concentrations in the pontine reticular formation (-14.6%) and substantia innominata (-36.7%). Intravenous administration of buprenorphine significantly decreased (-20%) adenosine in the substantia innominata. CONCLUSIONS: Buprenorphine significantly increased time spent awake, decreased nonrapid eye movement sleep, and increased latency to sleep onset. These disruptions in sleep architecture were mitigated by coadministration of the nonbenzodiazepine sedative-hypnotic eszopiclone. The buprenorphine-induced decrease in adenosine concentrations in basal forebrain and pontine reticular formation is consistent with the interpretation that decreasing adenosine in sleep-regulating brain regions is one mechanism by which opioids disrupt sleep.

Thermal nociception is decreased by hypocretin-1 and an adenosine A1 receptor agonist microinjected into the pontine reticular formation of Sprague Dawley rat.

UNLABELLED: Clinical and preclinical data concur that sleep disruption causes hyperalgesia, but the brain mechanisms through which sleep and pain interact remain poorly understood. Evidence that pontine components of the ascending reticular activating system modulate sleep and nociception encouraged the present study testing the hypothesis that hypocretin-1 (orexin-A) and an adenosine receptor agonist administered into the pontine reticular nucleus, oral part (PnO) each alter thermal nociception. Adult male rats (n = 23) were implanted with microinjection guide tubes aimed for the PnO. The PnO was microinjected with saline (control), hypocretin-1, the adenosine A(1) receptor agonist N(6)-p-sulfophenyladenosine (SPA), the hypocretin receptor-1 antagonist N-(2-Methyl-6-benzoxazolyl)-N''-1,5-naphthyridin-4-yl-urea (SB-334867), and hypocretin-1 plus SB-334867. As an index of antinociceptive behavior, the latency (in seconds) to paw withdrawal away from a thermal stimulus was measured following each microinjection. Compared to control, antinociception was significantly increased by hypocretin-1 and by SPA. SB-334867 increased nociceptive responsiveness, and administration of hypocretin-1 plus SB-334867 blocked the antinociception caused by hypocretin-1. These results suggest for the first time that hypocretin receptors in rat PnO modulate nociception. PERSPECTIVE: Widely distributed and overlapping neural networks regulate states of sleep and pain. Specifying the brain regions and neurotransmitters through which pain and sleep interact is an essential step for developing adjunctive therapies that diminish pain without disrupting states of sleep and wakefulness.

Opioid-induced decreases in rat brain adenosine levels are reversed by inhibiting adenosine deaminase.

BACKGROUND: Opioids disrupt sleep and adenosine promotes sleep, but no studies have characterized the effects of opioids on adenosine levels in brain regions known to regulate states of arousal. Delivering opioids to the pontine reticular formation (PRF) and substantia innominata (SI) region of the basal forebrain disrupts sleep. In contrast, administering adenosine agonists to the PRF or SI increases sleep. These findings encouraged the current study testing the hypothesis that microdialysis delivery of opioids to the PRF or SI decreases adenosine levels in the PRF or SI, respectively. METHODS: A microdialysis probe was placed in the PRF of isoflurane anesthetized rats and perfused with Ringer's solution (control) followed by Ringer's solution containing morphine (0, 10, 30, 100, or 300 microm), fentanyl (100 microm), morphine (100 microm) and the adenosine deaminase inhibitor EHNA (100 microm), or naloxone (10 microm) and morphine (100 microm). Additional experiments measured adenosine levels in the SI before and during microdialysis delivery of morphine, fentanyl, and morphine plus EHNA. RESULTS: Morphine caused a significant (P < 0.05) concentration-dependent decrease in PRF adenosine levels. The significant decrease (-20%) in adenosine caused by 100 microm morphine was blocked by coadministration of naloxone. Fentanyl also significantly decreased (-13.3%) PRF adenosine. SI adenosine levels were decreased by morphine (-26.8%) and fentanyl (-27.4%). In both PRF and SI, coadministration of morphine and EHNA prevented the significant decrease in adenosine levels caused by morphine alone. CONCLUSIONS: These data support the interpretation that decreased adenosine levels in sleep-regulating brain regions may be one of the mechanisms by which opioids disrupt sleep.

Influence of glutamatergic projections to the rostral pontine reticular formation on micturition in rats.

AIMS: We examined the effect of injecting glutamate or a glutamate receptor antagonist into the rostral pontine reticular formation (RPRF) on the micturition reflex in anesthetized rats and conscious rats. MAIN METHOD: Forty-eight female rats were divided into an isovolumetric cystometry group and a continuous cystometry group. Under urethane anesthesia or while conscious, physiological saline, glutamate, or MK-801 (a glutamate receptor antagonist) was injected into the RPRF, and then the changes of bladder activity were examined. KEY FINDINGS: There was no significant change of bladder activity after injection of physiological saline. In anesthetized rats, the injection of either glutamate or MK-801 into the RPRF transiently inhibited bladder contractions. There was a complete recovery of bladder activity 10-20 min after glutamate or MK-801 injection and there were no significant changes of cystometry parameters after the recovery of bladder contractions. In conscious rats, injection of glutamate into the RPRF prolonged the interval between bladder contractions and decreased the baseline bladder pressure. On the other hand, injection of MK-801 into the RPRF caused numerous small bladder contractions, some of which were accompanied by a leakage of a small amount of fluid from around the urethral catheter. SIGNIFICANCE: RPRF neurons receive glutamatergic projections, possibly from the forebrain, and the RPRF inhibits the micturition reflex pathway. RPRF neurons are also regulated by inhibitory interneurons, which receive glutamatergic projections as well. Therefore, the RPRF plays an important role in the regulation of urine storage.

Involvement of pallidotegmental neurons in methamphetamine- and MK-801-induced impairment of prepulse inhibition of the acoustic startle reflex in mice: reversal by GABAB receptor agonist baclofen.

We have previously demonstrated that pallidotegmental GABAergic neurons play a crucial role in prepulse inhibition (PPI) of the startle reflex in mice through the activation of GABA(B) receptors in pedunculopontine tegmental neurons. In this study, we investigated whether PPI disruption induced by methamphetamine (METH) or MK-801 is associated with the dysfunction of pallidotegmental neurons. Furthermore, we examined the effects of baclofen, a GABA(B) receptor agonist, on METH- and MK-801-induced PPI impairment. Acute treatment with METH (3 mg/kg, subcutaneouly (s.c.)) and MK-801 (>0.3 mg/kg, s.c.) significantly disrupted PPI, accompanied by the suppression of c-Fos expression in lateral globus pallidus induced by PPI. Furthermore, acute treatment with METH and MK-801 stimulated c-Fos expression in the caudal pontine reticular nucleus (PnC) in mice subjected to the PPT test, although PPI alone had no effect on c-Fos expression. Repeated treatment with 1 mg/kg METH for 7 days, which did not affect PPI acutely, showed similar effects on PPI and c-Fos expression to acute treatment with METH (3 mg/kg). Baclofen dose-dependently ameliorated PPI impairment induced by acute treatment with METH (3 mg/kg) and MK-801 (1 mg/kg), and decreased METH- and MK-801-stimulated c-Fos expression in PnC to the basal level. These results suggest that dysfunction of pallidotegmental neurons is involved in PPI disruption caused by METH and MK-801 in mice. GABA(B) receptor may constitute a putative target in treating neuropsychiatric disorders with sensorimotor gating deficits, such as schizophrenia and METH psychosis.

Chemical stimulation of visceral afferents activates medullary neurones projecting to the central amygdala and periaqueductal grey.

Cholecystokinin (CCK) stimulates gastrointestinal vagal afferent neurones that signal visceral sensations. We wished to determine whether neurones of the nucleus of the solitary tract (NTS) or ventrolateral medulla (VLM) convey visceral afferent information to the central nucleus of the amygdala (CeA) or periaqueductal grey region (PAG), structures that play a key role in adaptive autonomic responses triggered by stress or fear. Male Sprague-Dawley rats received a unilateral microinjection of the tracer cholera toxin subunit B (CTB, 1%) into the CeA or PAG followed, 7 days later, by an injection of CCK (100 microg/kg, i.p.) or saline. Brains were processed for detection of Fos protein (Fos-IR) and CTB. CCK induced increased expression of Fos-IR in the NTS and the VLM, relative to control. When CTB was injected into the CeA, CTB-immunoreactive (CTB-IR) neurones were more numerous in the rostral NTS ipsilateral to the injection site, whereas they were homogeneously distributed throughout the VLM. Double-labelled neurones (Fos-IR+CTB-IR) were most numerous in the ipsilateral NTS and caudal VLM. The NTS contained the higher percentage of CTB-IR neurones activated by CCK. When CTB was injected into the PAG, CTB-IR neurones were more numerous in the ipsilateral NTS whereas they were distributed relatively evenly bilaterally in the rostral VLM. Double-labelled neurones were not differentially distributed along the rostrocaudal axis of the NTS but were more numerous in this structure when compared with the VLM. NTS and VLM neurones may convey visceral afferent information to the CeA and the PAG.

Involvement of 5-HT(2) serotonergic receptors of the nucleus raphe magnus and nucleus reticularis gigantocellularis/paragigantocellularis complex neural networks in the antinociceptive phenomenon that follows the post-ictal immobility syndrome.

The post-ictal immobility syndrome is followed by a significant increase in the nociceptive thresholds in animals and men. In this interesting post-ictal behavioral response, endogenous opioid peptides-mediated mechanisms, as well as cholinergic-mediated antinociceptive processes, have been suggested. However, considering that many serotonergic descending pathways have been implicated in antinociceptive reactions, the aim of the present work is to investigate the involvement of 5-HT(2)-serotonergic receptor subfamily in the post-ictal antinociception. The analgesia was measured by the tail-flick test in seven or eight Wistar rats per group. Convulsions were followed by statistically significant increase in the tail-flick latencies (TFL), at least for 120 min of the post-ictal period. Male Wistar rats were submitted to stereotaxic surgery for introduction of a guide-cannula in the rhombencephalon, aiming either the nucleus raphe magnus (NRM) or the gigantocellularis complex. In independent groups of animals, these nuclei were neurochemically lesioned with a unilateral microinjection of ibotenic acid (1.0 microg/0.2 microL). The neuronal damage of either the NRM or nucleus reticularis gigantocellularis/paragigantocellularis complex decreased the post-ictal analgesia. Also, in other independent groups, central administration of ritanserin (5.0 microg/0.2 microL) or physiological saline into each of the reticular formation nuclei studied caused a statistically significant decrease in the TFL of seizing animals, as compared to controls, in all post-ictal periods studied. These results indicate that serotonin input-connected neurons of the pontine and medullarly reticular nuclei may be involved in the post-ictal analgesia.

Dialysis delivery of an adenosine A2A agonist into the pontine reticular formation of C57BL/6J mouse increases pontine acetylcholine release and sleep.

In vivo microdialysis in C57BL/6J (B6) mouse was used to test the hypothesis that activating adenosine A(2A) receptors in the pontine reticular formation (PRF) increases acetylcholine (ACh) release and rapid eye movement (REM) sleep. Eight concentrations of the adenosine A(2A) receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine hydrochloride (CGS 21680; CGS) were delivered to the PRF and ACh in the PRF was quantified. ACh release was significantly increased by dialysis with 3 mum CGS and significantly decreased by dialysis with 10 and 100 microm CGS. Co-administration of the adenosine A(2A) receptor antagonist 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385; 30 nM) blocked the CGS-induced increase in ACh release. In a second series of experiments, CGS (3 microm) was delivered by dialysis to the PRF for 2 h while recording sleep and wakefulness. CGS significantly decreased time in wakefulness (-51% in h 1; -54% in h 2), increased time in non-rapid eye movement (NREM) sleep (90% in h 1; 151% in h 2), and increased both time in REM sleep (331% in h 2) and the number of REM sleep episodes (488% in h 2). The enhancement of REM sleep is consistent with the interpretation that adenosine A(2A) receptors in the PRF of the B6 mouse contribute to REM sleep regulation, in part, by increasing ACh release in the PRF. A(2A) receptor activation may promote NREM sleep via GABAergic inhibition of arousal promoting neurons in the PRF.

Nicotine suppresses the P13 auditory evoked potential by acting on the pedunculopontine nucleus in the rat.

We identified a potential novel site of action for nicotine (NIC) since (a) systemic injection of NIC led to a dose-dependent decrease in the amplitude of the sleep state-dependent, vertex-recorded, P13 midlatency auditory evoked potential (generated by the reticular activating system, RAS), (b) localized injections of a nicotinic receptor antagonist into the pedunculopontine nucleus (PPN, the cholinergic arm of the RAS) blocked the effects of systemic NIC on the P13 potential (a measure of level of arousal), and (c) localized injection of a nicotinic receptor agonist into the PPN also led to a decrease in the amplitude of the P13 potential, an effect blocked by PPN injection of a nicotinic receptor antagonist. There were minor changes in the manifestation of the startle response (SR) at the concentrations used; however, NIC did decrease the hippocampal N40 potential, although its effects were not affected by antagonist or agonist injections into the PPN. These results suggest a potential mechanism underlying the anxiolytic effects of NIC-suppression of the cholinergic arm of the RAS.

Effects of anesthetics on hypoglossal nerve discharge and c-Fos expression in brainstem hypoglossal premotor neurons.

This study examined the effects of anesthesia on the hypoglossal nerve and diaphragm activities and on c-Fos expression in brainstem hypoglossal premotor neurons (pmXII). Experiments were performed in 71 rats by using halothane inhalation, pentobarbital sodium, or mixtures of alpha-chloralose and urethane or ketamine and xylazine. First, various cardiorespiratory parameters were measured in the rats (n = 31) during both awake and anesthetized conditions. The volatile anesthetic halothane, but not the other anesthetics, was always associated with a strong phasic inspiratory activity in the hypoglossal nerve. Second, a double-immunohistochemical study was performed in awake and anesthetized rats (n = 40) to gauge the level of activity of pmXII neurons. Brainstem pmXII neurons were identified after microiontophoresis of the retrograde tracer Fluoro-Gold in the right hypoglossal motor nucleus. Patterns of c-Fos expression at different brainstem levels were compared in five groups of rats (i.e., awake or anesthetized with halothane, pentobarbital, chloralose-urethane, and ketamine-xylazine). Sections were processed for double detection of c-Fos protein and Fluoro-Gold by using the standard ABC method and a two-color peroxidase technique. Anesthesia with halothane induced the strongest c-Fos expression in a restricted pool of pmXII located in the pons at the level of the Kölliker-Fuse nucleus and the intertrigeminal region. The results demonstrated a major effect of halothane in inducing changes in hypoglossal activity and revealed a differential expression of c-Fos protein in pmXII neurons among groups of anesthetized rats. We suggest that halothane mediates changes in respiratory hypoglossal nerve discharge by altering activity of premotor neurons in the Kölliker-Fuse and intertrigeminal region.

Granulocyte macrophage colony-stimulating factor regulates activity of the nervous system.

OBJECTIVES: The peripheral administration of granulocyte macrophage colony-stimulating factor (GM-CSF), widely used for the treatment of cytopenias, is often associated with neurological effects [Lieschke et al., N Engl J Med 1992;327:28-34]. This cytokine has recently been reported to affect neurotransmitter metabolism in the nervous system [Bianchi, Neuroreport 1997;8:3587-3590]. To further investigate the neuromodulatory effect of GM-CSF we studied the influence of GM-CSF on the efferent electric activity in the splenic nerve and the integral neuronal activity in medullary gigantocellular reticular formation (MGRF) in rats. METHODS: Anaesthetized (sodium thiopental 70 mg/kg, i.p.) Wistar rats were injected subcutaneously with 1 microg/kg of hr GM-CSF. Efferent electric activity in the splenic nerve and integral electric activity in MGRF were analyzed. The effectiveness of the applied dose of GM-CSF was verified by determining the elevation of the white blood cell count in peripheral blood 60 min after injection. RESULTS: We found that GM-CSF increases efferent electric activity in the splenic nerve and decreases that of MGRF as is evident by the frequency of electric discharges. The latency of both effects was 5-15 min. CONCLUSIONS: This data support the view that GM-CSF exerts a neuromodulatory effect and may provide a new link of neuroimmune communication.

Dialysis delivery of an adenosine A1 receptor agonist to the pontine reticular formation decreases acetylcholine release and increases anesthesia recovery time.

BACKGROUND: Adenosine modulates cell excitability, acetylcholine release, nociception, and sleep. Pontine cholinergic neurotransmission contributes to the generation and maintenance of electroencephalographic and behavioral arousal. Adenosine A(1) receptors inhibit arousal-promoting, pontine cholinergic neurons, and adenosine enhances sleep. No previous studies have determined whether pontine adenosine also modulates recovery from anesthesia. Therefore, the current study tested the hypotheses that dialysis delivery of the adenosine A(1) receptor agonist N6-p-sulfophenyladenosine (SPA) into the pontine reticular formation would decrease acetylcholine release and increase the time needed for recovery from halothane anesthesia. METHODS: A microdialysis probe was positioned in the pontine reticular formation of halothane-anesthetized cats. Probes were perfused with Ringer's solution (control) followed by the adenosine A(1) receptor agonist SPA (0.088 or 8.8 mm). Dependent measures included acetylcholine release and a numeric assessment of recovery from anesthesia. An intensive, within-subjects design and analysis of variance evaluated SPA's main effect on acetylcholine release and anesthetic recovery. The adenosine A(1) receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 100 microm) was coadministered with SPA to test for antagonist blocking of SPA's effects. RESULTS: SPA significantly (P < 0.0001) decreased acetylcholine release in the pontine reticular formation and significantly (P < 0.0001) delayed recovery from anesthesia. Coadministration of SPA and DPCPX caused no decrease in acetylcholine release or delay in postanesthetic recovery. Dialysis delivery of SPA into the cerebellar cortex confirmed that the SPA effects were site-specific to the pontine reticular formation. CONCLUSION: The results provide a novel extension of the sleep-promoting effects of adenosine by showing that pontine delivery of an adenosine A(1) receptor agonist delays resumption of wakefulness following halothane anesthesia. This extension is consistent with a potentially larger relevance of the current findings for efforts to specify neurons and molecules causing physiologic and behavioral traits comprising anesthetic states. These data support the conclusion that adenosine A(1) receptors in medial regions of the pontine reticular formation, known to modulate sleep, also contribute to the generation and/or maintenance of halothane anesthesia.

Endogenous and exogenous dopamine presynaptically inhibits glutamatergic reticulospinal transmission via an action of D2-receptors on N-type Ca2+ channels.

In this study, the effects of exogenously applied and endogenously released dopamine (DA), a powerful modulator of the lamprey locomotor network, are examined on excitatory glutamatergic synaptic transmission between reticulospinal axons and spinal neurons. Bath application of DA (1-50 micro m) reduced the amplitude of monosynaptic reticulospinal-evoked glutamatergic excitatory postsynaptic potentials (EPSPs). The effect of DA was blocked by the D2-receptor antagonist eticlopride, and mimicked by the selective D2-receptor agonist 2,10,11 trihydroxy-N-propyl-noraporphine hydrobromide (TNPA). Bath application of the DA reuptake blocker bupropion, which increases the extracellular level of dopamine, also reduced the monosynaptic EPSP amplitude. This effect was also blocked by the D2-receptor antagonist eticlopride. To investigate if the action of DA was exerted at the presynaptic level, the reticulospinal axon action potentials were prolonged by administering K+ channel antagonists while blocking l-type Ca2+ channels. A remaining Ca2+ component, mainly dependent on N and P/Q channels, was depressed by DA. When DA (25-50 micro m) was applied in the presence of omega-conotoxin GVIA, a toxin specific for N-type Ca2+ channels, it failed to affect the monosynaptic EPSP amplitude. DA did not affect the response to extracellularly ejected d-glutamate, the postsynaptic membrane potential, or the electrical component of the EPSPs. DA thus acts at the presynaptic level to modulate reticulospinal transmission.