sfn2004

Leung LS, Petropoulos S, Ma J, Shen B (2004) Cholinergic neurons in the basal forebrain participate in consciousness and general anesthesia. Neuroscience 2004 Abstracts 565.4. Society for Neuroscience, San Diego, CA.

Summary: Acetylcholine (Ach) in the brain has long been associated with consciousness. In this study, we assessed consciousness in rats by their EEG and behavioral responses to a general anesthetic. Cholinergic neurons in the nucleus basalis of Meynert (NbM) were lesioned by bilateral injection of toxin IgG192-saporin (0.15 μg at P1.4, L2.7, 7.7 mm below dura) in 10 adult male rats. Control (5 rats) had saline injected into the NbM. EEGs were recorded by electrodes placed in layer V of the frontal cortex (FC) and visual cortex (VC). Spectral analysis of the spontaneous EEGs in FC and VC during awake-immobility indicated that lesioned animals showed higher delta (0.8 to 4 Hz) and lower gamma (30- 58 Hz) power as compared to controls. Subsequent acetylcholinesterase staining (optical density) confirmed significant Ach depletion in both FC and VC, in the lesion as compared to the control group (P<0.002, Wilcoxon). When challenged with a normally subanesthetic dose of general anesthetic, the lesioned rats showed, as compared to controls, significantly longer durations of loss of righting and tail-pinch response after 5 mg/kg i.v. propofol (P<0.001), but not after 20 mg/kg i.p. pentobarbital or 2% halothane. In correspondence with the deep behavioral anesthesia, delta power at FC after propofol was significantly larger in lesioned than control rats. Lesioned rats, as compared to controls, also showed decreased locomotion (behavioral excitation) when given 2% halothane in a large chamber. In summary, a loss of Ach in the neocortex decreases the level of consciousness as indicated by increased delta and decreased gamma EEG, and by an increased sedative/ anesthetic response to propofol i.v. We suggest that patients with Alzheimer disease may show altered response to some general anesthetics.

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

Nattie EE, Li A (2004) Brainstem catecholaminergic neurons participate in central chemoreception in NREM sleep and wakefulness. Neuroscience 2004 Abstracts 145.9. Society for Neuroscience, San Diego, CA.

Summary: In the locus ceruleus (LC), noradrenergic neurons are CO2 sensitive in vitro and focal acidification stimulates breathing in vivo. Do catecholaminergic (CA) neurons in general have a like role? To kill brainstem CA neurons we administered a conjugate of the cell toxin saporin with an antibody to dopamine-β-hydroxylase via the fourth ventricle in rats (N=7) using IgG-saporin conjugate injections as a control (N=6). We studied breathing in air, 3 and 7% CO2 during NREM sleep and wakefulness before and 7, 14, and 21 days after the injections. TH-ir noradrenergic neurons were significantly reduced in LC (-84%) and the A5 region (-78%) but not the A9 region. PNMT-ir adrenergic neurons were significantly reduced in C3 (-56%) and C1 (-60%) regions. Neither treatment affected room air breathing. In 3 and 7% CO2, IgG-SAP injections had no effect. In the lesion group, during 3% CO2 frequency (f) was significantly decreased (two-way ANOVA) and Δ ventilation (VE) (VE in 5% CO2 – VE in air) was significantly decreased in sleep. During 7% CO2, both absolute and Δ VE and f were significantly decreased in sleep and wakefulness, Δ VE by 25% in wakefulness and 28% in sleep at 21 days. Brainstem CA neurons participate in central chemoreception in vivo during both NREM sleep and wakefulness.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

Sundararaman N, Vertes RP, Perry GW (2004) Neurotoxic lesions of serotonin containing cells of the median raphe nucleus produce constant hippocampal theta rhythm in behaving rats. Neuroscience 2004 Abstracts 196.15. Society for Neuroscience, San Diego, CA.

Summary: The median raphe nucleus (MR) is a major serotonin containing cell group with pronounced projections to the forebrain. The MR exerts strong desynchronizing actions on the EEG activity of the hippocampus. MR stimulation desynchronizes the hippocampal EEG (or blocks theta), and electrolytic MR lesions produce continuous theta. Evidence suggests that desynchronizing actions of MR on the hippocampal EEG are mediated by serotonergic (5-HT) cells of MR. Injections of pharmacological agents into MR that suppress 5-HT MR activity generate theta at short latencies and for long durations. We examined the effects of the selective destruction of 5-HT cells of MR using the 5-HT neurotoxin, anti-SERT-SAP (Advanced Targeting Systems) on the EEG activity of the hippocampus in behaving rats. Under deep sodium pentobarbital anesthesia, rats were chronically prepared with bipolar electrodes, bilaterally in the dorsal hippocampus, a cortical screw for recording the cortical EEG and an indwelling cannula placed 3-4 mm dorsal to MR for the injection of anti-SERT-SAP into MR. Following a 5-7 day period of recovery, hippocampal EEG activity was recorded daily for 7 days as rats freely moved about in a shielded enclose, and then re-assessed under the same conditions following neurotoxic lesions. We found that neurotoxic lesions of MR that resulted in a substantial destruction of 5-HT MR cells (80-90%) produced a continuous theta rhythm in rats; that is, during locomotor behavior as well as during states when theta is normally absent, such as immobility and grooming. For some rats, theta was equivalent during complete immobility and active movement. These results support earlier findings that 5-HT cells of MR are directly involved in the desynchronization of the hippocampal EEG, and indicate that the MR exerts a powerful modulatory influence on the hippocampus.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Wiley RG, Kline IV, RHLappi DA (2004) Intrathecal galanin-saporin and NPY-saporin reduce nocifensive responses to noxious heat and formalin. Neuroscience 2004 Abstracts 292.15. Society for Neuroscience, San Diego, CA.

Summary: Although the precise circuitry of the dorsal horn underlying nociception is not fully understood, there is evidence that regulation of the excitability of nociceptive projection neurons is influenced/modulated by excitatory interneurons. The present study sought to determine if selectively destroying presumed excitatory interneurons in the superficial dorsal horn would alter nocifensive responses to noxious thermal or chemical stimuli. The strategy chosen was to inject saporin (SAP) conjugates of either galanin (GAL) or neuropeptide Y (NPY) into the lumbar subarachnoid space and then test rats on the hotplate and observe the nocifensive responses to hindpaw formalin injection. After hotplate testing for 2 weeks, staining for c-fos expression in the dorsal horn was performed 2 hrs after hindpaw formalin injection. Lumbar intrathecal injection of 500 ng of either GAL-SAP or NPY-SAP produced no obvious change in appearance, body weight or spontaneous activity of adult male Sprague-Dawley rats. Both toxins reduced responses on the 44 C hotplate but not at 52 C. Nocifensive responses to the 47 C hotplate also were reduced but not as strikingly as at 44 C. Responses to hindpaw formalin were remarkably different. Toxin-injected rats held the injected foot close to the body, off the floor, throughout the 90 minute observation period but otherwise ignored the injected paw. Unlike controls, toxin-injected rats did not shake, lick or bite the injected hindpaw and showed normal exploratory behavior. These results are interpreted as showing that these two toxins likely destroy excitatory interneurons in the superficial dorsal horn resulting in decreased excitability of nociceptive projection neurons, and therefor reduced sensitivity to noxious thermal and chemical stimuli.

Related Products: NPY-SAP (Cat. #IT-28), Galanin-SAP (Cat. #IT-34)

King CD, Baker B, Gu JG, Vierck CJ, Yezierski RP (2004) Behavioral evidence for a capsaicin-sensitive inhibitory pathway (CSIP): A novel modulatory role for substance P. Neuroscience 2004 Abstracts 292.18. Society for Neuroscience, San Diego, CA.

Summary: Exposure to noxious thermal stimulation or application of capsaicin cream causes the release of SP from capsaicin-sensitive primary afferent terminals that activate neurokinin-1 receptor (NK1R) expressing neurons in the superficial dorsal horn. Recent evidence suggests the existence of a capsaicin-sensitive inhibitory pathway (CSIP), a novel inhibitory mechanism that involves NK1R expressing neurons in laminae III-V. To determine the functional significance of these NK1R expressing neurons, substance P-saporin neurotoxin (SP-SAP) was used to ablate NK1R neurons in the superficial laminae. Elimination of the NK1R neurons in this region made it possible to evaluate the modulatory effects of NK1R expressing inhibitory neurons in deeper laminae. Reflexive responses were evaluated in rats during a 10-minute trial at 44.5°C before (pre-) and 14 days after (post-) intrathecal injection of 350ng SP-SAP. Testing conditions included: 1) baseline; 2) hindpaw application of 1% capsaicin cream; and, 3) intrathecal injection of the NK1 antagonist CP-97,345 following hindpaw application of 1% capsaicin cream. In normal rats, hindpaw application of capsaicin produced thermal hyperalgesia. In contrast, application of capsaicin produced a hypoalgesia in the same rats after treatment with SP-SAP. The capsaicin-induced hyperalgesia in normal rats was blocked by CP-97,345. The antagonist also blocked the capsaicin-induced hypoalgesia in SP-SAP rats. In conclusion, it is suggested that substance P activates inhibitory interneurons in the deep dorsal horn. The inhibitory effect initiated by substance P on pain transmission neurons represents a novel role of substance P in the spinal processing of nociceptive information.

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

Abe T, Shimoda T, Sugiyo S, Ohshita N, Takao T, Takemura M (2004) Altered effects of systemic bicuculline on intensity-dependent c-Fos expression in rats ablated with NK-1 receptor-bearing neurons in the trigeminal caudal nucleus. Neuroscience 2004 Abstracts 294.12. Society for Neuroscience, San Diego, CA.

Summary: In rats pretreated with saporin conjugated to substance P (SP-Sap: 5 μM, 5 μl) into cisterna magna, the numbers of neurons-immunoreactive for NK-1 receptor (NK-1R) in laminae I and III of trigeminal caudal nucleus (Vc) were significantly decreased compared with rats similarly treated with saline (Sal; 5 μl) or blank-saporin (Bl-Sap; 5 μM, 5 μl). We examined the effects of selective ablation of NK-1R-bearing neurons and systemic administration of bicuculline (2 mg/kg, i.p.) on the expression of c-Fos induced 2 hr after electrical stimulation (5 Hz, 5 ms) of the trigeminal ganglion (TG) at low (0.1 mA) and high intensities (1.0 mA). In Sal- or Bl-Sap treated rats, 10 min stimulation at 0.1 and 1.0 mA of the TG induced c-Fos-immunoreactive (c-FosIR) cells in the ipsilateral superficial layers of the Vc (VcI/II) in a intensity-dependent manner. In rats treated with SP-Sap, and stimulated at 1.0 mA but not at 0.1 mA, the numbers of c-FosIR cells in the Vc were significantly decreased compared to Sal- or Bl-Sap treated rats. In Sal- or Bl-Sap treated rats preadministed with bicuculline and stimulated at 0.1 mA and 1.0 mA, the numbers of c-FosIR cells in VcI/II were significantly increased and decreased, respectively. However, in SP-Sap treated rats preadministered with bicuculline and stimulated at 0.1 mA and 1.0 mA, the numbers of c-FosIR cells in VcI/II were significantly increased. These results indicate that NK-1R-bearing neurons in the Vc have pivotal role in the modality and/or intensity-dependent sensory (nociceptive) processing in the TSN through GABAA receptors.

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

Ralston HJ, Wiley RG, Dougherty PM, Weng HR, Cata J, Chen JH, Hopkins SD, Canchola SA, Galo E, Vierck CJ (2004) The effects of chronic deafferentation and SSP-saporin on pain responses, spinal cord neurons and on the structure and function of the somatosensory thalamus (VPL) in the macaque monkey. Neuroscience 2004 Abstracts 295.1. Society for Neuroscience, San Diego, CA.

Summary: We have used behavioral, physiological and anatomical methods to examine the effects of chronic (> 2 years) lesions of the dorsal column pathway and of the intrathecal administration of the neurotoxin SSP-saporin in adult M. arctoides. Normal animals were evaluated to determine their responses to noxious heat (52 to 58°C) applied to the lower limbs. Subsequently, the monkeys were anesthetized and had unilateral lesions of the dorsal and dorsolateral spinal cord white matter pathways at midthoracic levels. After recovering from the surgery, their pain responses were studied for more than 1 year, following which SSP-saporin was administered to the lumbosacral spinal cord. The animals were found to have a decrease in their responses to noxious heat applied to the lower limbs. Terminal physiological experiments revealed that the neurons within the lower limb representation of VPL on the side contralateral to the thoracic cord lesion did not have normal receptive fields, although some cells responded to stimulation of both upper and lower limbs. Histological sections of lumbar spinal cord were stained for neurokinin 1 receptor (NK-1R) and showed a significant decrease in lamina I NK-1R positive neurons. Electron microscopy of VPL revealed patterns of synaptic terminals that were different than those found in VPL of normal macaques. We will determine whether there is a significant correlation between the altered behaviors and the physiological and anatomical changes in these animals as a consequence of somatosensory deafferentation.

Related Products: SSP-SAP (Cat. #IT-11)

Wei F, Zou S, Robbins MT, Ren K, Dubner R (2004) Mu-opioid receptor-expressing neurons in the nucleus reticularis gigantocellularis contribute to descending facilitation during the development of inflammatory pain. Neuroscience 2004 Abstracts 297.3. Society for Neuroscience, San Diego, CA.

Summary: We have previously shown that nucleus reticularis giangocellularis (NGC) is involved in descending facilitation of inflammatory hyperalgesia. The cellular mechanisms of descending facilitation from the NGC are unknown. The targeted destruction of the mu-opioid receptor-containing neurons in the rostral ventromedial medulla (RVM) by a dermorphin-saporin conjugate prevents nerve injury-induced hyperalgesia in rats (Porreca et al., J. Neurosci. 21:5281, 2001). We examined the effects of selective deletion of the mu-opioid receptor-expressing neurons in the sub-regions of RVM on nocifensive behaviors in rats. After microinjection of dermorphin-saporin conjugate (1.5 pmol/500 nl) into the RVM, there were no changes in baseline thermal and mechanical sensitivity to noxious stimuli. However, the injection of dermorphin-saporin conjugate into bilateral NGC (n=7) significantly attenuated the thermal hyperalgesia and mechanical allodynia at 30 min to 1 d after hindpaw inflammation produced by injection of complete Freund’s adjuvant, compared to sham (blank-saporin or dermorphin) groups (n=3-6). The lesion of the nucleus raphe magnus (NRM) (n=3) only slightly reduced hyperalgesia at 3 h after inflammation. The loss of NGC mu-opioid receptor-containing neurons also decreased nocifensive behaviors only in phase II of the formalin model. In contrast, NRM lesions were without an effect on formalin-induced phase I/II responses. These findings indicate that selective deletion of the mu-opioid receptor-containing neurons in the nucleus reticularis giangocellularis attenuates inflammatory hyperagesia and allodynia.

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

Fargo KN, Sengelaub DR (2004) Prevention of depletion-induced motoneuron dendritic atrophy requires testosterone effects on target musculature. Neuroscience 2004 Abstracts 310.10. Society for Neuroscience, San Diego, CA.

Summary: Motoneurons in the spinal nucleus of the bulbocavernosus (SNB) in male rats project to the penile muscles bulbocavernosus (BC) and levator ani (LA). These motoneurons share a midline location, have intermingled somata, extensive dendritic overlap, and common afferents, and organize coordinated contractions of the penile musculature. Unilateral depletion of BC-projecting motoneurons causes marked dendritic atrophy in contralateral BC-projecting motoneurons, and this atrophy can be prevented with testosterone (T) treatment. In this experiment, we test whether the depletion-induced atrophy is related to the innervation of homotypic muscles. BC-projecting motoneurons were depleted by unilateral injection with saporin conjugated to the cholera toxin B subunit (SAP); some animals were simultaneously treated with T. Four weeks later, a period demonstrated to be sufficient to observe dendritic atrophy in remaining motoneurons, HRP conjugated to the cholera toxin B subunit (BHRP) was injected into the ipsilateral LA. SAP injection into the BC muscle killed over 40% of ipsilateral SNB motoneurons. Dendritic length in LA-projecting motoneurons was reduced by almost 60%. Because the SAP-induced depletion of motoneurons and the resultant dendritic atrophy occurred across motor populations, this result indicates that the dendritic atrophy we have observed previously is not restricted to motoneurons projecting to homotypic muscles. In previous studies, prevention of dendritic atrophy by T treatment in BC-projecting motoneurons was accompanied by a marked hypertrophy of the BC muscle. In the present experiment, T treatment failed to prevent dendritic atrophy in LA-projecting motoneurons, and further did not result in hypertrophy of the LA ipsilateral to the SAP-injected BC. Thus, it appears the neuroprotective effect of T treatment on SNB motoneurons may be dependent on T effects in the target musculature.

Related Products: CTB-SAP (Cat. #IT-14)

Broussard JI, Sarter M, Givens B (2004) Neuronal correlates of signal detection in rat posterior parietal cortex. Neuroscience 2004 Abstracts 331.6. Society for Neuroscience, San Diego, CA.

Summary: The posterior parietal cortex (PPC) has been shown to be involved in the attentional processing of visual stimuli. Recent evidence has indicated that neuronal activity in the PPC is increased during the detection of signals, and this activation is modulated by visual distractors. We tested the hypothesis that detected signals are associated with increased PPC unit activity. Animals were trained in a sustained attention task using signal and nonsignal trials. After training to criterion (>75% accuracy), we implanted moveable stereotrodes into the PPC. A visual distractor was presented in a block of trials during testing sessions and effects on performance and single unit activity were examined. We also evaluated the effects of varying signal duration on performance and single unit activity. PPC neurons (39/111) exhibited a significantly greater response during signal trials than during nonsignal trials. The presentation of visual signals produced a robust increase in neuronal activity prior to the performance of a hit, but not prior to a miss, both of which required a lever press. Analysis of signal duration indicated that shorter signals resulted in fewer hits. PPC neurons became active when the signal was accurately detected, independent of signal duration. Shorter signals activated the PPC on fewer trials, which was associated with a lower likelihood for detection. The visual distractor reduced both the signal-driven unit activity and the relative number of hits. These findings suggest that activation of the PPC is associated with the detection of visual signals. We are currently investigating the effects of local cholinergic deafferentation (via 192 IgG saporin) on signal driven neuronal activity in the PPC. These studies will elucidate the contribution of basal forebrain cholinergic innervation to attentional processing in the PPC.

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