Induced Fos Expression Research Articles

Role of pterygopalatine ganglion in regulating isoflurane-induced cerebral hyper-perfusion.

Cerebral perfusion is functionally regulated by neural mechanisms in addition to the systemic hemodynamic variation, vascular reactivity and cerebral metabolism. Although anesthesia is generally esteemed to suppress the overall brain neural activity and metabolism, a few inhalation anesthetics, such as isoflurane, can increase cerebral perfusion, thus heightening the risks of higher intracranial pressure, bleeding, and brain edema during surgery. With the aid of laser speckle contrast imaging, we observed a transient yet limited effect of cerebral perfusion enhancement in mice from awake to anesthetized conditions with different concentration of isoflurane. Retrograde and antegrade tracing revealed a higher proportion of parasympathetic control more than sympathetic innervation for the blood vessels. Surprisingly, isoflurane directly activated pterygopalatine ganglion (PPG) explants and induced FOS expression in the cholinergic neurons. Chemogenetic activation of cholinergic PPG neurons reduced isoflurane-related cerebral perfusion. On the contrary, ablation of the cholinergic PPG neurons resulted in further enhancement of cerebral perfusion induced by isoflurane. While blocking muscarinic cholinergic receptors resulted in the overall reduction upon isoflurane stimulation, the blockage of nicotinic cholinergic receptors enhanced the isoflurane-induced cerebral perfusion only when PPG neurons exist. Collectively, these results suggest that PPG play important roles in regulating cerebral perfusion under isoflurane inhalation.

Subregion and sex differences in ethanol activation of cholinergic and glutamatergic cells in the mesopontine tegmentum

Ethanol engages cholinergic signaling and elicits endogenous acetylcholine release. Acetylcholine input to the midbrain originates from the mesopontine tegmentum (MPT), which is composed of the laterodorsal tegmentum (LDT) and the pedunculopontine tegmental nucleus (PPN). We investigated the effect of acute and chronic ethanol administration on cholinergic and glutamatergic neuron activation in the PPN and LDT in male and female mice. We show that ethanol activates neurons of the PPN and not the LDT in male mice. Chronic 15 daily injections of 2 g/kg ethanol induced Fos expression in cholinergic and glutamatergic PPN neurons in male mice, whereas ethanol did not increase cholinergic and glutamatergic neuronal activation in the LDT. A single acute 4 g/kg injection, but not a single 2 g/kg injection, induced cholinergic neuron activation in the male PPN but not the LDT. In contrast, acute or chronic ethanol at either dose or duration had no effect on the activation of cholinergic or glutamatergic neurons in the MPT of female mice. Female mice had higher baseline level of activation in cholinergic neurons compared with males. We also found a population of co-labeled cholinergic and glutamatergic neurons in the PPN and LDT which were highly active in the saline- and ethanol-treated groups in both sexes. These findings illustrate the complex differential effects of ethanol across dose, time point, MPT subregion and sex.

Central administered xenin induced Fos expression in nesfatin-1 neurons in rats

Xenin is a 25-amino acid peptide identified in human gastric mucosa, which is widely expressed in peripheral and central tissues. It is known that the central or peripheral administration of xenin decreases food intake in rodents. Nesfatin-1/NUCB2 (nesfatin-1) has been identified as an anorexic neuropeptide, it is often found co-localized with many peptides in the central nervous system. After the intracerebroventricular administration of xenin on nesfain-1-like immunoreactivity (LI) neurons, we examined its effects on food intake and water intake in rats. As a result, Fos-LI neurons were observed in the organum vasculosum of the laminae terminalis (OVLT), the median preoptic nucleus (MnPO), the subfornical organ (SFO), the supraoptic nucleus (SON), the paraventricular nucleus (PVN), the arcuate nucleus (Arc), the lateral hypothalamic area (LHA), the central amygdaloid nucleus (CAN), the dorsal raphe nucleus (DR), the locus coeruleus (LC), the area postrema (AP) and the nucleus of the solitary tract (NTS). After the administration, the number of Fos-LI neurons was significantly increased in the LC and the OVLT, the MnPO, the SFO, the SON, the PVN, the Arc, the LHA, the CAN, the DR, the AP and the NTS, compared with the control group. After the administration of xenin, we conducted double immunohistochemistry for Fos and nesfatin-1, and found that the number of nesfatin-1-LI neurons expressing Fos were significantly increased in the SON, the PVN, the Arc, the LHA, the CAN, the DR, the AP and the NTS, compared with the control group. The pretreatment of nesfatin-1 antisense significantly attenuated this xenin-induced feeding suppression, while that of nesfatin-1 missense showed no improvement. These results indicate that central administered xenin may have anorexia effects associated with activated central nesfatin-1 neurons.

The astrocytic Na+ -HCO3 - cotransporter, NBCe1, is dispensable for respiratory chemosensitivity.

The interoceptive homeostatic mechanism that controls breathing, blood gases and acid-base balance in response to changes in CO2 /H+ is exquisitely sensitive, with convergent roles proposed for chemosensory brainstem neurons in the retrotrapezoid nucleus (RTN) and their supporting glial cells. For astrocytes, a central role for NBCe1, a Na+ -HCO3 - cotransporter encoded by Slc4a4, has been envisaged in multiple mechanistic models (i.e. underlying enhanced CO2 -induced local extracellular acidification or purinergic signalling). We tested these NBCe1-centric models by using conditional knockout mice in which Slc4a4 was deleted from astrocytes. In GFAP-Cre;Slc4a4fl/fl mice we found diminished expression of Slc4a4 in RTN astrocytes by comparison to control littermates, and a concomitant reduction in NBCe1-mediated current. Despite disrupted NBCe1 function in RTN-adjacent astrocytes from these conditional knockout mice, CO2 -induced activation of RTN neurons or astrocytes in vitro and in vivo, and CO2 -stimulated breathing, were indistinguishable from NBCe1-intact littermates; hypoxia-stimulated breathing and sighs were likewise unaffected. We obtained a more widespread deletion of NBCe1 in brainstem astrocytes by using tamoxifen-treated Aldh1l1-Cre/ERT2;Slc4a4fl/fl mice. Again, there was no difference in effects of CO2 or hypoxia on breathing or on neuron/astrocyte activation in NBCe1-deleted mice. These data indicate that astrocytic NBCe1 is not required for the respiratory responses to these chemoreceptor stimuli in mice, and that any physiologically relevant astrocytic contributions must involve NBCe1-independent mechanisms. KEY POINTS: The electrogenic NBCe1 transporter is proposed to mediate local astrocytic CO2 /H+ sensing that enables excitatory modulation of nearby retrotrapezoid nucleus (RTN) neurons to support chemosensory control of breathing. We used two different Cre mouse lines for cell-specific and/or temporally regulated deletion of the NBCe1 gene (Slc4a4) in astrocytes to test this hypothesis. In both mouse lines, Slc4a4 was depleted from RTN-associated astrocytes but CO2 -induced Fos expression (i.e. cell activation) in RTN neurons and local astrocytes was intact. Likewise, respiratory chemoreflexes evoked by changes in CO2 or O2 were unaffected by loss of astrocytic Slc4a4. These data do not support the previously proposed role for NBCe1 in respiratory chemosensitivity mediated by astrocytes.

Effects of 5-HT2C receptor stimulation in male mice on behaviour and Fos expression: Feeding, reward and impulsivity

Serotonin modulates many motivated behaviours via multiple receptor subtypes. Agonists at 5-HT2C receptors have potential for treating behavioural problems associated with obesity and drug use. In this work we examined the impact of the 5-HT2C receptor agonist lorcaserin on several motivated behaviours related to feeding, reward and waiting impulsivity, and on neuronal activation in key brain areas mediating those behaviours. In male C57BL/6J mice effects of lorcaserin (0.2, 1 and 5 mg/kg) were examined on feeding, and on operant responding for a palatable reward. Feeding was reduced only at 5 mg/kg, whereas operant responding was reduced at 1 mg/kg. At a much lower dose range lorcaserin 0.05–0.2 mg/kg also reduced impulsive behaviour measured as premature responding in the 5-choice serial reaction time (5-CSRT) test, without affecting attention or ability to perform the task. Lorcaserin induced Fos expression in brain regions related to feeding (paraventricular nucleus and arcuate nucleus), reward (ventral tegmental area), and impulsivity (medial prefrontal cortex, VTA) although these effects did not show the same differential sensitivity to lorcaserin as the behavioural measures. These results indicate a broad profile of action of 5-HT2C receptor stimulation on brain circuitry and on motivated behaviours, but with clear evidence of differential sensitivity across behavioural domains. This is exemplified by the fact that impulsive behaviour was reduced at a much lower dose range than was feeding behaviour. Along with previous work, and some clinical observations, this work supports the idea that 5-HT2C agonists may be useful for behavioural problems associated with impulsivity.

A brainstem circuit for nausea suppression.

SUMMARYNausea is a discomforting sensation of gut malaise that remains a major clinical challenge. Several visceral poisons induce nausea through the area postrema, a sensory circumventricular organ that detects blood-borne factors. Here, we use genetic approaches based on an area postrema cell atlas to reveal inhibitory neurons that counteract nausea-associated poison responses. The gut hormone glucose insulinotropic peptide (GIP) activates area postrema inhibitory neurons that project locally and elicit inhibitory currents in nausea-promoting excitatory neurons through γ-aminobutyric acid (GABA) receptors. Moreover, GIP blocks behavioral responses to poisons in wild-type mice, with protection eliminated by targeted area postrema neuron ablation. These findings provide insights into the basic organization of nausea-associated brainstem circuits and reveal that area postrema inhibitory neurons are an effective pharmacological target for nausea intervention.

Combinatorial Treatment with PARP-1 Inhibitors and Cisplatin Attenuates Cervical Cancer Growth through Fos-Driven Changes in Gene Expression.

Our observations, which link the gene regulatory effects of PARPi + cisplatin to the growth inhibitory effects of FOS expression in cervical cancer cells, strengthen the rationale for using PARPi with cisplatin as a therapy for cervical cancer.

Parvalbumin Neurons in Zona Incerta Regulate Itch in Mice.

Pain and itch are intricately entangled at both circuitry and behavioral levels. Emerging evidence indicates that parvalbumin (PV)-expressing neurons in zona incerta (ZI) are critical for promoting nocifensive behaviors. However, the role of these neurons in itch modulation remains elusive. Herein, by combining FOS immunostaining, fiber photometry, and chemogenetic manipulation, we reveal that ZI PV neurons act as an endogenous negative diencephalic modulator for itch processing. Morphological data showed that both histamine and chloroquine stimuli induced FOS expression in ZI PV neurons. The activation of these neurons was further supported by the increased calcium signal upon scratching behavior evoked by acute itch. Behavioral data further indicated that chemogenetic activation of these neurons reduced scratching behaviors related to histaminergic and non-histaminergic acute itch. Similar neural activity and modulatory role of ZI PV neurons were seen in mice with chronic itch induced by atopic dermatitis. Together, our study provides direct evidence for the role of ZI PV neurons in regulating itch, and identifies a potential target for the remedy of chronic itch.

Low Fos expression in newly generated neurons of the main and accessory olfactory bulb following single maternal separation

The main and accessory olfactory bulbs (MOB and AOB) are unique in that they produce new neurons throughout adulthood. Despite the recent knowledge about the involvement of postnatally generated cells in several aspects of olfaction, the functional role of these neurons is still not sufficiently understood. The function of newly generated olfactory bulb neurons is primarily investigated in relation to activities related to smell. Stress-induced activation of new olfactory neurons has not yet been studied. Thus, our work was aimed to investigate whether a stressful event, such as maternal separation (MS) can induce Fos expression in postnatally-born neurons in the MOB and AOB. Rat pups were exposed to single maternal separation (SMS) for 2 h at the postnatal days: P7, P14, and P21. Quantification of immunohistochemically labeled Fos + cells revealed that exposure to SMS in different age stages during the first postnatal month stimulates activity in cells of individual MOB/AOB layers in an age-dependent manner. In order to find out whether newly generated cells in the MOB/AOB could express Fos protein as a response to SMS, newborn rats were administrated with the marker of proliferation, bromodeoxyuridine (BrdU) at P0, and three weeks later (at P21) colocalization of Fos and BrdU in the neurons of the MOB and AOB was assessed. Quantitative analysis of BrdU/Fos double-labeled cells showed that Fos is expressed only in a small number of postnatally generated cells within the MOB/AOB. Our results indicate that postnatally generated MOB/AOB neurons are less sensitive to stress caused by MS than preexisting ones. LAY SUMMARY Our results showed that single maternal separation (SMS) is a stressful event that in age-dependent manner stimulates cellular activity in the main and accessory olfactory bulb (AOB) – the structures dedicated to odor information processing. The low level of Fos expression in newborn neurons of the main and accessory bulb indicates that postnatally generated cells are less sensitive to neonatal stress than preexisting neurons.

Hypnotic effect of thalidomide is independent of teratogenic ubiquitin/proteasome pathway

Thalidomide exerts its teratogenic and immunomodulatory effects by binding to cereblon (CRBN) and thereby inhibiting/modifying the CRBN-mediated ubiquitination pathway consisting of the Cullin4-DDB1-ROC1 E3 ligase complex. The mechanism of thalidomide's classical hypnotic effect remains largely unexplored, however. Here we examined whether CRBN is involved in the hypnotic effect of thalidomide by generating mice harboring a thalidomide-resistant mutant allele of Crbn (Crbn YW/AA knock-in mice). Thalidomide increased non-REM sleep time in Crbn YW/AA knock-in homozygotes and heterozygotes to a similar degree as seen in wild-type littermates. Thalidomide similarly depressed excitatory synaptic transmission in the cortical slices obtained from wild-type and Crbn YW/AA homozygous knock-in mice without affecting GABAergic inhibition. Thalidomide induced Fos expression in vasopressin-containing neurons of the supraoptic nucleus and reduced Fos expression in the tuberomammillary nuclei. Thus, thalidomide's hypnotic effect seems to share some downstream mechanisms with general anesthetics and GABAA-activating sedatives but does not involve the teratogenic CRBN-mediated ubiquitin/proteasome pathway.

Fos expression is increased in oxytocin neurons of female rats with a sexually conditioned mate preference for an individual male rat

Evidence suggests an important role of Pavlovian learning in sexual partner selection. Female rats that experience paced copulation with a male scented with a neutral odor selectively solicit and receive ejaculations from the scented male relative to an unscented male. Exposure to the conditioned odor alone induces Fos protein in regions of the brain associated with sexual excitation. Here we tested whether female rats can be conditioned to show a sexual preference for an unscented male rat of the same strain. Female Long-Evans rats were given 10 copulatory trials with either a one-hole pacing divider or a four-hole pacing divider in a unilevel chamber with the same conspecific male (n = 16). Females were then given an open-field partner preference test with the paired male versus a novel male. After two reconditioning trials females were exposed to the partner or a novel male to induce Fos expression. Females that paced with the one-hole divider received the first ejaculation and more ejaculations overall from the paired compared to novel male. Fos immunoreactivity within oxytocin neurons in the PVN, mPOA, and VMH was increased in females with a preference that were exposed to the paired male. These data indicate that female rats can form selective sexual preferences for an individual conspecific and that their formation depends on the type of pacing during conditioning. These findings further suggest the involvement of oxytocin in the display of conditioned preferences. Thus, early copulatory experience appears to determine the mating strategy used by female rats.

Prolactin-induced and neuronal activation in the brain of mother mice.

Nursing has important consequences on mothers. To separate the prolactin-mediated and the neuronally-mediated actions of nursing, neurons directly affected by prolactin were visualized using pSTAT5 immunohistochemistry in relation to Fos-expressing neurons in suckled mother mice. In response to pup exposure following 22-h pup deprivation, we found a markedly elevated number of pSTAT5-containing neurons in several brain regions, including the lateral septum, medial amygdaloid nucleus, subparafascicular area, caudal periaqueductal gray, dorsal raphe, lateral parabrachial nucleus, nucleus of the solitary tract, and the periventricular, medial preoptic, paraventricular, arcuate and ventromedial nuclei of the hypothalamus. Pup exposure also induced Fos expression in all of these brain regions except the arcuate and ventromedial hypothalamic nuclei. Bromocriptine treatment known to reduce prolactin levels eliminated pSTAT5 from most brain regions while it did not affect Fos activation following suckling. The degree of colocalization for pSTAT5 and Fos ranged from 8 to 80% in the different brain regions suggesting that most neurons responding to pup exposure in mother mice are driven either by prolactin or direct neuronal input from the pups, while the number of neurons affected by both types of inputs depends on the examined brain area. In addition, both pSTAT5 and Fos were also double-labeled with estrogen receptor alpha (ERα) in mother mice, which revealed a very high degree of colocalization between pSTAT5 and ERα with much less potential interaction between Fos- and ERα-containing neurons suggesting that estrogen-sensitive neurons are more likely to be affected by prolactin than by direct neuronal activation.

Peripheral ionotropic glutamate receptors contribute to Fos expression increase in the spinal cord through antidromic electrical stimulation of sensory nerves

Previous studies have shown that peripheral ionotropic glutamate receptors are involved in the increase in sensitivity of a cutaneous branch of spinal dorsal ramus (CBDR) through antidromic electrical stimulation (ADES) of another CBDR in the adjacent segment. CBDR in the thoracic segments run parallel to each other and no synaptic contact at the periphery is reported. The present study investigated whether the increased sensitivity of peripheral sensory nerves via ADES of a CBDR induced Fos expression changes in the adjacent segments of the spinal cord. Fos expression increased in the T8 - T12 segments of the spinal cord evoked by ADES of the T10 CBDR in rats. The increased Fos expression in the T11 and T12, but not T8 - T10 spinal cord segments, was significantly blocked by local application of either N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine maleate (MK-801) or non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) into the receptive field of T11 CBDR. The results suggest that endogenous glutamate released by ADES of sensory nerve may bind to peripheral ionotropic glutamate receptors and activate adjacent sensory nerve endings to increase the sensitivity of the spinal cord. These data reveal the potential mechanisms of neuron activation in the spinal cord evoked by peripheral sensitization.

Normal behavioral responses to light and darkness and the pupillary light reflex are dependent upon the olivary pretectal nucleus in the diurnal Nile grass rat

The olivary pretectal nucleus (OPT) is a midbrain structure that receives reciprocal bilateral retinal projections, is involved in the pupillary light reflex, and connects reciprocally with the intergeniculate leaflet (IGL), a retinorecipient brain region that mediates behavioral responses to light pulses (i.e., masking) in diurnal Nile grass rats. Here, we lesioned the OPT and evaluated behavioral responses in grass rats to various lighting conditions, as well as their anxiety-like responses to light exposure. While control grass rats remained diurnal, grass rats with OPT lesions exhibited a more night-active pattern under 12h:12h light–dark (LD) conditions. However, when placed in constant darkness, OPT-lesioned grass rats became more active during their subjective day, suggesting that an exaggerated masking response to light may be responsible for the effect of OPT lesions on locomotor activity in LD. To test this hypothesis, we presented dark and light pulses to controls and grass rats with OPT lesions; controls increased their activity in response to light, whereas those with OPT lesions significantly increased activity in response to darkness. Further, when placed in a 7-h ultradian LD cycle, animals with OPT lesions were more active during darkness than controls. OPT lesions also abolished the pupillary light reflex, but did not affect anxiety-like behaviors. Finally, in animals with OPT lesions, light did not induce Fos expression in the ventrolateral geniculate nucleus, as it did in controls. Altogether, these results suggest that masking responses to light and darkness are dependent upon nuclei within the subcortical visual shell in grass rats.

NERP-2 regulates gastric acid secretion and gastric emptying via the orexin pathway

Neuroendocrine regulatory peptide (NERP)-2 is derived from a distinct region of VGF, a neurosecretory protein originally identified as a product of a nerve growth factor-responsive gene in rat PC12 cells. Colocalization of NERP-2 with orexin-A in the lateral hypothalamus increases orexin-A-induced feeding and energy expenditure in both rats and mice. Orexigenic and anorectic peptides in the hypothalamus modulate gastric function. In this study, we investigated the effect of NERP-2 on gastric function in rats. Intracerebroventricular administration of NERP-2 to rats increased gastric acid secretion and gastric emptying, whereas peripheral administration did not affect gastric function. NERP-2-induced gastric acid secretion and gastric emptying were blocked by an orexin 1 receptor antagonist, SB334867. NERP-2 also induced Fos expression in the lateral hypothalamus and the dorsomotor nucleus of the vagus X, which are key sites in the central nervous system for regulation of gastric function. Atropine, a blocker of vagal efferent signal transduction, completely blocked NERP-2-induced gastric acid secretion. These results demonstrate that central administration of NERP-2 activates the orexin pathway, resulting in elevated gastric acid secretion and gastric emptying.

Effect of Melanotan‐II on Brain Fos Immunoreactivity and Oxytocin Neuronal Activity and Secretion in Rats

Melanocortins stimulate the central oxytocin systems that are involved in regulating social behaviours. Alterations in central oxytocin have been linked to neurological disorders such as autism, and melanocortins have been proposed for therapeutic treatment. In the present study, we investigated how systemic administration of melanotan-II (MT-II), a melanocortin agonist, affects oxytocin neuronal activity and secretion in rats. The results obtained show that i.v., but not intranasal, administration of MT-II markedly induced Fos expression in magnocellular neurones of the supraoptic (SON) and paraventricular nuclei (PVN) of the hypothalamus, and this response was attenuated by prior i.c.v. administration of the melanocortin antagonist, SHU-9119. Electrophysiological recordings from identified magnocellular neurones of the SON showed that i.v. administration of MT-II increased the firing rate in oxytocin neurones but did not trigger somatodendritic oxytocin release within the SON as measured by microdialysis. Our data suggest that, after i.v., but not intranasal, administration of MT-II, the activity of magnocellular neurones of the SON is increased. Because previous studies showed that SON oxytocin neurones are inhibited in response to direct application of melanocortin agonists, the actions of i.v. MT-II are likely to be mediated at least partly indirectly, possibly by activation of inputs from the caudal brainstem, where MT-II also increased Fos expression.

The cholinergic forebrain arousal system acts directly on the circadian pacemaker

Sleep and wake states are regulated by a variety of mechanisms. One such important system is the circadian clock, which provides temporal structure to sleep and wake. Conversely, changes in behavioral state, such as sleep deprivation (SD) or arousal, can phase shift the circadian clock. Here we demonstrate that the level of wakefulness is critical for this arousal resetting of the circadian clock. Specifically, drowsy animals with significant power in the 7- to 9-Hz band of their EEGs do not exhibit phase shifts in response to a mild SD procedure. We then show that treatments that both produce arousal and reset the phase of circadian clock activate (i.e., induce Fos expression in) the basal forebrain. Many of the activated cells are cholinergic. Using retrograde tract tracing, we demonstrate that cholinergic cells activated by these arousal procedures project to the circadian clock in the suprachiasmatic nuclei (SCN). We then demonstrate that arousal-induced phase shifts are blocked when animals are pretreated with atropine injections to the SCN, demonstrating that cholinergic activity at the SCN is necessary for arousal-induced phase shifting. Finally, we demonstrate that electrical stimulation of the substantia innominata of the basal forebrain phase shifts the circadian clock in a manner similar to that of our arousal procedures and that these shifts are also blocked by infusions of atropine to the SCN. These results establish a functional link between the major forebrain arousal center and the circadian system.

Genetic Isolation of Hypothalamic Neurons that Regulate Context-Specific Male Social Behavior.

Nearly all animals engage in a complex assortment of social behaviors that are essential for the survival of the species. In mammals, these behaviors are regulated by sub-nuclei within the hypothalamus, but the specific cell types within these nuclei responsible for coordinating behavior in distinct contexts are only beginning to be resolved. Here, we identify a population of neurons in the ventral premammillary nucleus of the hypothalamus (PMV) that are strongly activated in male intruder mice in response to a larger resident male but that are not responsive to females. Using a combination of molecular and genetic approaches, we demonstrate that these PMV neurons regulate intruder-specific male social behavior and social novelty recognition in a manner dependent on synaptic release of the excitatory neurotransmitter glutamate. These data provide direct evidence for a unique population of neurons that regulate social behaviors in specific contexts.

In vivo dopamine agonist properties of rotigotine: Role of D1 and D2 receptors

Rotigotine acts in vitro as a full agonist of dopamine D1 receptors at concentrations almost superimposable to those at which it acts on D2 receptors. However in vivo evidence of the differences between the agonist activity of rotigotine at D1 receptors from that on the D2 receptors has not been provided yet. In order to test the ability of rotigotine to stimulate dopamine D1 and D2 receptors in vivo, we studied the effect of SCH39166 and eticlopride, selective dopamine D1 and D2/D3 receptor antagonists respectively, on rotigotine-induced contralateral turning behavior in 6-hydroxydopamine lesioned rats. Furthermore, the expression of the immediate-early gene c-fos in the caudate-putamen, was evaluated. As a comparison, we tested the D2/D3 agonist pramipexole. In primed rats, rotigotine (0.035, 0.1 and 0.35mg/kg) induced dose-dependent contralateral turning. Turning induced by 0.1mg/kg of rotigotine was reduced by pretreatment with the D1 antagonist SCH39166 and the D2 antagonist eticlopride. In drug-naive rats, rotigotine was less effective in eliciting turning but SCH39166 still reduced turning induced by rotigotine (0.35mg/kg). Pramipexole induced contralateral turning only in primed rats. SCH39166 potentiated and eticlopride abolished pramipexole-induced turning. Rotigotine induced Fos expression in the caudate-putamen and SCH39166 completely blocked it. Pramipexole failed to induce Fos. These results indicate that rotigotine acts in vivo as an agonist of D1 and D2 receptors while pramipexole is devoid of D1 activity in vivo. Given their differing DA receptor profiles, rotigotine and pramipexole might differ in their spectrum of application to the therapy of Parkinson's disease.

Effects of prazosin and doxazosin on yohimbine-induced reinstatement of alcohol seeking in rats.

Alpha-1 adrenoceptor antagonists, such as prazosin, show promise in treating alcoholism. In rats, prazosin reduces alcohol self-administration and relapse induced by footshock stress and the alpha-2 antagonist yohimbine, but the processes involved in these effects of prazosin are not known. Here, we present studies on the central mechanisms underlying the effects of prazosin on yohimbine-induced reinstatement of alcohol seeking. In experiment 1, we trained rats to self-administer alcohol (12% w/v, 1h/day), extinguished their responding, and tested the effects of prazosin, administered ICV (2 and 6nmol) or systemically (1mg/kg) on yohimbine (1.25mg/kg)-induced reinstatement. In experiment 2, we determined potential central sites of action by analyzing effects of prazosin (1mg/kg) on yohimbine (1.25mg/kg)-induced Fos expression. In experiment 3, we determined the effects of doxazosin (1.25, 2.5, and 5mg/kg), an alpha-1 antagonist with a longer half-life on yohimbine-induced reinstatement. Yohimbine-induced reinstatement of alcohol seeking was reduced significantly by ICV and systemic prazosin (50 and 69% decreases, respectively). Systemic prazosin reduced yohimbine-induced Fos expression in the prefrontal cortex, accumbens shell, ventral bed nucleus of the stria terminalis, and basolateral amygdala (46-67% decreases). Doxazosin reduced yohimbine-induced reinstatement of alcohol seeking (78% decrease). Prazosin acts centrally to reduce yohimbine-induced alcohol seeking. The Fos mapping study suggests candidate sites where it may act. Doxazosin is also effective in reducing yohimbine-induced reinstatement. These data provide information on the mechanisms of alpha-1 antagonists on yohimbine-induced alcohol seeking and indicate their further investigation for the treatment of alcoholism.