sfn2006

Frederick-Duus D, Fadel J (2006) Orexin transmission is required for food-related increases in cortical acetylcholine release. Neuroscience 2006 Abstracts 369.23. Society for Neuroscience, Atlanta, GA.

Summary: The hypothalamic orexin/hypocretin neuropeptides (OxA and OxB) are crucial modulators of state-dependent behavior including the regulation of arousal in response to homeostatic challenges. Orexins provide a moderately dense innervation of cholinergic portions of the basal forebrain, including the ventral pallidum/substantia innominata and nucleus basalis magnocellularis. OxA administration in this area also produces robust increases in cortical acetylcholine (ACh) release. Here, we used in vivo microdialysis to test the hypothesis that orexin transmission is required for the increase in cortical ACh release resulting from presentation of stimuli related to palatable food. Rats were mildly food-deprived and trained to associate sudden darkness in the testing room with presentation of sweetened cereal. Stimulated cortical ACh release in these animals was blocked by orexin B-saporin (OxB-SAP) lesions of the perifornical hypothalamus at doses that produced 75-80% loss of orexin neurons, but minimal loss of other neuronal phenotypes in this area. In intact animals, pretreatment with the orexin 1 receptor (Ox1R) antagonist SB334867 similarly abolished food cue-elicited increases in cortical ACh release, indicating the specific involvement of OxA in this phenomenon. Neither OxB-SAP nor SB334867 reduced affected basal ACh release. Finally, in old rats (28-30 months), double-label immunohistochemistry revealed a reduction in orexin-immunoreactive fibers near cholinergic somata and dendrites in the basal forebrain regions, consistent with the deficits in stimulated ACh release seen with old animals in this paradigm. Collectively, these data suggest that phasic orexin activation of the basal forebrain cholinergic system may bias attentional resources toward stimuli related to underlying homeostatic challenges, thus coordinating the processing of interoceptive and exteroceptive cues. Age-related deficits in these capacities may have an orexinergic basis.

Related Products: Orexin-B-SAP (Cat. #IT-20)

Broussard JI, Venugopal S, Sarter M, Givens B (2006) Cholinergic modulation of posterior parietal neuronal activity associated with the detection of signals in attentional task-performing rats. Neuroscience 2006 Abstracts 369.7. Society for Neuroscience, Atlanta, GA.

Summary: The posterior parietal cortex (PPC) is considered a major component of the brains’ attention systems, specifically of the orientation control network. This network controls the selection of stimuli, especially if stimuli are presented at unpredictable or multiple locations. Thus, mechanisms optimizing stimulus detection are hypothesized to represent fundamental components of the processes mediated via neuronal circuitry involving the PPC. Previous studies indicated the role of basal forebrain cholinergic projections to the cortex in the detection of signals. Furthermore, we demonstrated that performance of an attentional task involving signal detection activates PPC neurons in rat, specifically if signals are followed by a behavioral response indicating successful detection. The present experiment was designed to test the hypothesis that signal detection-related activation of PPC neurons depends on the integrity of cholinergic inputs to the PPC. Animals were trained to perform an operant sustained attention task involving signal detection as well as responding to non-signal events. Animals were equipped with a drivable headstage to insert stereotrodes into the PPC. After recording PPC neuronal activity during several baseline sessions, including the effects of a distractor, cholinergic projections to the PPC were lesioned by infusing 192 IgG-saporin into the recording region. Recordings from control animals prior to and after saline infusions (599 neurons total) indicate that PPC neurons (56 %) display increases in single unit activity evoked by detected visual signals. Presentation of a visual distractor reduced the number of signal detections but did not alter the detection-associated firing characteristics of PPC neurons, and relatively few neurons were modulated by the onset or offset of the distractor (8%). Unilateral, restricted removal of cholinergic inputs to the PPC did not affect the animals’ detection rate but reduced the proportion of neurons showing detection-related increases in neuronal activity (27 %). These data support the hypothesis that cholinergic inputs to the PPC mediates the detection of signals and thus contributes to the fundamental attentional processing mediated via PPC circuitry.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Likhtik E, Apergis-Schoute J, Pare D (2006) A selective lesioning method to probe the role of intercalated (ITC) amygdala neurons in the extinction of classically conditioned fear responses. Neuroscience 2006 Abstracts 370.19. Society for Neuroscience, Atlanta, GA.

Summary: The acquisition of conditioned fear responses (CRs) is thought to involve the potentiation of synapses conveying information about the conditioned stimulus (CS) to the basolateral (BLA) amygdala. Expression of CRs would depend on transfer of potentiated CS inputs by the BLA to the central amygdala (CE). In contrast, the mechanisms of extinction remain controversial. It was proposed that ITC neurons, which receive BLA inputs and generate feedforward inhibition in CE, are in a key position to mediate extinction. In this view, potentiation of BLA inputs to ITC cells during extinction training, would dampen the impact of CS-related BLA activity on CE neurons, inhibiting CRs. However, this idea is difficult to test because ITC cells occur in small, lateromedially dispersed clusters, making conventional lesioning methods inadequate. The present study aimed to find an effective way of eliminating ITC cells, taking advantage of the fact that, compared to the rest of the amygdala, they exhibit strong immunoreactivity for mu opioid receptors (muORs). First, we performed electron microscopic observations to determine whether muORs are expressed by ITC cells vs. afferents to ITC cells. This test revealed that muORs are concentrated in the postsynaptic membrane density of asymmetric synapses found on ITC cells. Next, we tested whether it is possible to obtain selective ITC lesions by injecting the toxin saporin conjugated to the mu opioid agonist dermorphin (DER-SAP) in the proximity of ITC cells. Thus, rats received intra-amygdaloid pressure injections of DER-SAP in one hemisphere and of vehicle on the contralateral side. Seven days later, the animals were perfused and the tissue processed to reveal muOR. DER-SAP injections produced a marked reduction in muOR immunoreactivity at the BLA-CE border, where ITC cells are usually located. Thus, selective lesioning of ITC cells can be achieved using this method. We are currently testing the impact of such ITC lesions on extinction learning.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

Iacobucci P, Colonnello V, Ricceri L (2006) Detailed analysis of ultrasound vocalizations emitted by 12-d-old rats during homing test: effects of a brief reunion with littermates in neonatal basal forebrain cholinergic lesioned pups. Neuroscience 2006 Abstracts 374.17. Society for Neuroscience, Atlanta, GA.

Summary: To evaluate the role of the developing cholinergic basal forebrain system on neonatal behavioural repertoire, seven day-old rats received lesions using intraventricular injections of 192 IgG-saporin or saline; on postnatal day (pnd) 12 we recorded ultrasonic vocalizations (USVs) emitted during a homing test (an olfactory based test carried out in a T-shaped arena to measure discrimination of home- versus non familiar- nest odors). USVs emitted by isolated 12-day-old pups were recorded during a first exposure to the homing test (4 min) and during a second exposure in the same setting (4 min), after a 1 min reunion with littermates. In all pups (control and 192 IgG-saporin) number of USVs (ranging between 30 and 60 kHz) significantly increased after reunion with littermates. Analysis of the sonographic structure of the pup calls identified 15 different classes of signals and revealed that the increase in USVs after reunion with littermates was due to a selective increase in 4-5 of the 15 classes [namely, constant frequency signals, brief calls (dot-shape), multiple sweeps calls (e.g. M- or W-shape), rising sweeps (/)]. Also time spent over the home-scented area increased during the second exposure to the homing test in all pups, but such increase was more evident in control than in cholinergic lesioned pups. Even if effects of the neonatal cholinergic lesions were limited, from a methodological point of view these results suggest that USV emission can be measured not only in standard neonatal isolation settings, but also while the subject is performing another neonatal behavioral task. Interestingly, the USV emission during the homing test is modulated by the rat pup after a brief reunion with littermates (a phenomenon resembling the “maternal potentiation”). Such modulation affects both quantitative and qualitative USV features, as well as the time spent by the pups over the home-scented area.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Chauhan NB (2006) Cholinergic immunolesioning produced tangle-like inclusions in TgCRND8 brain. Neuroscience 2006 Abstracts 271.8. Society for Neuroscience, Atlanta, GA.

Summary: Today’s Alzheimer’s disease (AD) research lacks a “complete” model that would represent both plaque and tangle pathology together with correlative memory deficits. Although currently developed transgenic model including APP/PS1/tau mutations do not “truly” represent AD because tangles observed in AD brain are independent of tau mutations. Subtly increased β-amyloid (Aβ) levels either due to familial mutations or sporadic causes, primarily targets pre-tangle cytopathology and degeneration of basal forebrain cholinergic neurons (BFCN) via deranged signaling of glygogen synthase kinase 3-beta (GSK3β)-, protein kinase A (PKA)-, and extracellular signal-regulated kinase (ERK2) of ERK-mitogen-activated protein kinase (MAPK) cascade, leading to reduced phosphorylation of cAMP responsive element binding protein (CREB) that results in synaptic and memory deficits much earlier than the emergence of classic AD-pathology. Thus, subtly elevated Aβ, together with BFCN deficits resulting from Aβ-induced deranged signaling, set up a vicious feedback loop to produce characteristic plaque- and tangle-pathology observed in AD. Based on these facts, we wished to test if selective lesioning of basal fore brain cholinergic neurons during the early stages of amyloid build-up will exacerbate tau phosphorylation and produce tangle-like inclusions in transgenic mice with APP mutations. We produced selective immunotoxic lesions of BFCN by injecting the BFCN-specific cholinergic immunotoxin, which is known to specifically target p75-expressing BFCN and spare p75-expressing cerebellar neurons (Mu-p75-Saporin, Advanced Targeting Systems, #IT-16), intracerebroventricularly (ICV) in TgCRND8 mice harboring Swedish (KM670/671NL) and Indiana (V717F) mutations. This model exhibited tangle-like inclusions, provoked already existing plaque pathology, and worsened already impaired behavioral deficits.

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Cortez AM, Amodeo D, Chavez C, Flesher M, Balbous M, Butt AE (2006) Selective 192 IgG-saporin lesions of the cholinergic basal forebrain impair negative patterning discrimination learning in rats. Neuroscience 2006 Abstracts 162.7. Society for Neuroscience, Atlanta, GA.

Summary: We have previously argued that the cholinergic nucleus basalis magnocellularis (NBM) is necessary for complex or “configural” association learning, but is not necessary for simple association learning. The current experiment further tests the hypothesis that the cholinergic basal forebrain is involved in configural association learning by examining the respective contributions of the NBM projections to neocortex and the medial septal (MS) projections to hippocampus in separate groups of rats. Rats with bilateral 192 IgG-saporin lesions of either the NBM or MS were tested in a negative patterning operant discrimination task. Rats were food-reinforced (+) for responding in the presence of a light (L+) or a tone (T+), but were not reinforced (-) for responding in the presence of the configural stimulus comprised of the light and tone presented simultaneously (LT-). We have previously shown that NBM lesions cause a transient but significant impairment in negative patterning discrimination learning. Consequently, we hypothesized a similar NBM lesion-induced impairment in the current experiment. Because hippocampus lesions cause dramatic disruptions in the acquisition of the negative patterning task, it was hypothesized that lesions of the cholinergic neurons of the MS would cause a greater degree of impairment than NBM lesions. Consistent with our hypotheses, NBM lesions retarded but did not prevent acquisition. MS lesions, in contrast, caused significantly greater impairments than NBM lesions. Rats in both lesion groups responded normally to L+ and T+ but responded more often to LT-. These findings demonstrate intact simple association learning but disrupted configural association following damage to the cholinergic neurons of the NBM or MS. Results suggest that cholinergic basal forebrain modulation of neocortex and hippocampus contributes to configural association learning.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Abitoye PA, Li P, Gibbs RB, Johnson DA (2006) Steroid sulfatase inhibitor (p-O-sulfamoyl) – tetradecanoyl tyramine (du-14) enhances memory retention in rats with cholinergic lesion. Neuroscience 2006 Abstracts 163.15. Society for Neuroscience, Atlanta, GA.

Summary: Previous studies have shown that altering the metabolism of neurosteroids via inhibition of steroid sulfatase (SSI) would reverse scopolamine induced amnesia. In this study we tested whether the SSI, DU-14 could enhance memory retention of foot shock in rats with a selective lesion of cholinergic neurons projecting from the medial septum to the hippocampus using a passive avoidance paradigm. Male Sprague-Dawley rats were infused with either 0.2 μg of 192 IgG-saporin (SAP), a selective cholinergic immunotoxin, or artificial cerebrospinal fluid (CSF) into the medial septum. One week later, the animals were placed into a passive avoidance apparatus and administered footshock trials (1 mA / 1 sec) until criterion (2 consecutive trials with a crossover latency of at least 5 min). On the next day, rats from SAP and CSF groups were then randomly assigned to receive DU-14 (30mg / kg) or corn oil (vehicle) daily for 6 days. Rats were tested for memory retention three hours after the last day dosing. DU-14 increased crossover latency by 74.5% in the CSF control group and 54.8% in SAP treated animals. In order to determine whether DU-14 or SAP treatment inhibited locomotor activity independent of memory, other animals were dosed with vehicle or DU-14 and crossover latency was tested before acquisition of footshock. There were no significant differences between treatment groups. These results suggest that steroid sulfatase inhibition may enhance memory retention in rats with hippocampal cholinergic lesion.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Rivat C, Vera-Portocarrero LP, Ibrahim MM, Mata HP, Stagg NJ, De Felice M, Porreca F, Malan TP (2006) Ascending and descending pathways support fentanyl-induced pain hypersensitivity with and without a surgical incision. Neuroscience 2006 Abstracts 248.10. Society for Neuroscience, Atlanta, GA.

Summary: Acutely administered the analgesic opioid fentanyl has been shown to enhance mechanical hypersensitivity in a model of surgical pain induced by hindpaw incision in the rat. Recent evidence showed the importance of descending pathways originating from the rostral ventromedial medulla (RVM) in opioid-induced hyperalgesia after sustained morphine administration. Such hyperalgesia is also associated with numerous neurochemical changes in primary afferent fibers and spinal dorsal horn, such as increased spinal dynorphin expression. These changes may activate ascending pathways, mediated in part by NK-1 neurotransmission. Here, we examined the roles of ascending and descending pathways in sensory hypersensitivity after acute fentanyl administration. Male Sprague-Dawley rats received 4 fentanyl (4×100 μg/kg, s.c.) or saline injections administered at 15 min intervals. Some animals also received an incision in the plantar hindpaw. Thermal hyperalgesia and tactile allodynia were measured daily. In control rats, fentanyl induced analgesia followed by an immediate and long-lasting hyperalgesia, as previously described. Fentanyl also enhanced pain sensitivity induced by plantar incision. In SP-saporin pretreated rats, fentanyl induced analgesia and a moderate long-lasting hyperalgesia. The SP-saporin pretreatment slightly reduced both hyperalgesia and allodynia in postoperative rats and, to a larger extent, in fentanyl treated rats. Lidocaine injection in the RVM completely reversed fentanyl-induced sensory hypersensitivity and fentanyl enhancement of incision-induced hyperalgesia and allodynia. A slight reduction of incision-induced sensory hypersensitivity was observed after lidocaine injection in rats without fentanyl pretreatment. Spinal dynorphin content increased by 30 ± 7% and 71 ± 33% in fentanyl and fentanyl/incision treated rats, respectively. These data support the crucial role of the descending pathways from the RVM in the fentanyl-induced hyperalgesia and the partial implication of the NK-1 receptor containing ascending pathways.

Related Products: SP-SAP (Cat. #IT-07)

Hayashida K, Clayton B, Ma W, Eisenach J (2006) Brain-derived neurotrophic growth factor from p75-expressing sensory afferents drives spinal noradrenergic fiber sprouting following nerve injury in rats. Neuroscience 2006 Abstracts 248.19. Society for Neuroscience, Atlanta, GA.

Summary: We previously showed that peripheral nerve injury in mice results in sprouting of noradrenergic (NA) fibers in the spinal cord, possibly reflecting a substrate for increased efficacy of α2-adrenoceptor agonists such as clonidine. Here we tested whether spinal NA fiber sprouting also occurs in rats after peripheral nerve injury and examined the role of brain derived neurotrophic factor (BDNF) for such sprouting. Ligation of L5 and L6 spinal nerves unilaterally in rats resulted in mechanical hypersensitivity of the paw ipsilateral to injury and sprouting of NA fibers in the dorsal horn of the lumbar spinal cord. BDNF content increased in L4-L6 dorsal root ganglia (DRG) ipsilateral to injury and in lumbar spinal cord following nerve injury and intrathecal infusion of BDNF antiserum prevented spinal NA sprouting. Pro-BDNF immunoreactivity increased in L4-L6 DRG neurons ipsilateral to injury, especially in large-size neurons, and was highly co-localized with the low affinity neurotrophin receptor, p75NTR. Intrathecal injection of anti-p75NTR linked to saporin destroyed p75NTR expressing afferents and reversed NA sprouting after nerve injury. Manipulations which blocked NA sprouting (BDNF antiserum, anti-p-75NTR saporin) also prevented the increased analgesic efficacy of intrathecal clonidine observed after nerve injury. These results suggest that increased BDNF synthesis and release from p75NTR expressing injured and uninjured sensory afferents drives spinal NA sprouting following nerve injury and this sprouting increase the capacity for analgesia from drugs which utilize the NA pathway.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Tait DS, Brown VJ, Farovik A, Theobald DE, Dalley JW, Robbins TW (2006) Lesions of the dorsal noradrenergic bundle impair attentional set-shifting in the rat. Neuroscience 2006 Abstracts 264.4. Society for Neuroscience, Atlanta, GA.

Summary: Rats with medial prefrontal cortex (mPFC) lesions are impaired in attentional set shifting (Birrell and Brown, 2000, J Nsci, 20:4320-4324). The mPFC receives multiple projections, but norepinephrine (NE) has previously been reported to modulate attention by its action in the mPFC (for review see Dalley et al., 2004, Nsci Biobeh Rev, 28:771-784), including shifting attentional set. Indeed, there is recent evidence that increasing NE in the mPFC by autoreceptor antagonism improves set-shifting performance in rats (Lapiz and Morilak, 2006, Nsci, 137:1039-1049). Furthermore, reduction of prefrontal NE by infusion of anti-DBH-saporin into PFC has been shown to impair attentional set-shifting in rats (Eichenbaum et al., 2003, SfN Abstract 940.7). The main source of noradrenergic input to the mPFC is from locus coerulus via the dorsal noradrenergic bundle (DNAB). This study examined the effect of lesions of the DNAB on the acquisition, maintenance and shifting of attentional set. Eleven male Lister-hooded rats received bilateral DNAB lesions by infusion of 6-hydroxydopamine (4μg in 2μl each side) at (nosebar -2.4mm) AP -6.0mm, ML ±1.0mm, DV -5.0mm (from dura). Twelve control rats received injections of vehicle. Rats learned to dig for bait in bowls then learned two simple discriminations – based on the bowls odor or the digging substrate – to a criterion of six consecutive correct trials. The next day, a series of discriminations tested acquisition of novel discriminations (both intra (ID) and extradimensional (ED)) and reversal learning. Trials to criterion, incorrect trials and dig-latencies were recorded and analysed. At conclusion of testing, brain tissue samples were analysed for NE content by HPLC-ECD. All rats required more trials to reverse previously learned associations, and to learn new discriminations when attentional refocusing was required (ED shift). Rats with DNAB lesions were unimpaired at reversal stages, but were impaired at the ED acquisition stage. Lesioned rats showed reductions of NE levels in mPFC (up to 95% in the infralimbic region, 89% in the prelimbic region and 93% in cingulate area Cg1). These data provide further evidence for the role of NE in attentional set-shifting, and combine with previous data to elucidate the mechanisms by which mPFC mediates attentional set-shifting in the rat.

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