targeted-toxins

Savage S, Ogren S, Olson L, Mattsson A (2007) Immunotoxin lesion of cholinergic nucleus basalis magnocellularis neurons in Lister hooded rats impair performance in a delayed matching-to-place task. Neuroscience 2007 Abstracts 840.1/TT24. Society for Neuroscience, San Diego, CA.

Summary: Central cholinergic systems play an important role in various aspects of cognition, and deficits in cortical cholinergic function have been implicated in the cognitive impairments associated with normal aging and dementia. Cholinergic dysfunctions have also been implicated in several neuropsychiatric disorders, including schizophrenia. Though cognitive dysfunctions, such as impaired working memory, are observed in Alzheimer, as well as schizophrenic patients, the cholinergic mechanisms behind these dysfunctions are not well characterized in animal models. To investigate whether specific cortical cholinergic deficits will affect spatial learning and memory functions, we lesioned the basalo-cortical cholinergic system by stereotaxic infusion of the immunotoxin 192 IgG-saporin in the nucleus basalis magnocellularis (NBM) of adult male Lister hooded rats. Learning and memory was assessed using a delayed matching-to-place (DMP) paradigm in the water maze. We found that animals with cholinergic denervation of neocortex were impaired in the DMP-task. Thus, while the sham-operated animals rapidly learned the task without prior training, saporin-treated rats showed impairment during the initial three days of testing. By the end of the testing period, the lesioned animals had acquired the task. However, the cholinergically denervated animals showed a performance deficit throughout the duration of the experiment with higher trial latencies and longer distance traveled to find the platform as compared to the controls. They also seemed to employ a different strategy to find the hidden platform as compared to control animals. Whether the deficits after cholinergic lesions to the NBM seen in the present experiment are mnemonic and/or attentional in nature remains to be elucidated.

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

Contreras M, Carrasco M, Riveros M, Quispe M, Valdes J, Torrealba F (2007) Early activation of the tuberomammillary nucleus is a common factor in appetitive behaviors in rats. Neuroscience 2007 Abstracts 842.19/WW11. Society for Neuroscience, San Diego, CA.

Summary: Histamine neurons of the tuberomammillary nucleus show an earlier activation during the appetitive phase of feeding, compared to the other arousal system nuclei. To test if in different appetitive behaviors also these histaminergic neurons become active first, we studied changes in Fos-ir in arousal nuclei during sexual, drinking and drug-seeking behavior. Male rats were exposed to sexually receptive or to non-receptive female rats, allowing sensory but not sexual contact. Receptive females elicited increased sniffing time which positively correlated with Fos-ir in the dorsal raphe, laterodorsal tegmental nucleus, orexin hypothalamic neurons and tuberomammillary nucleus. Non receptive females induced less sniffing and no increased Fos-ir. Other male rats were deprived of water for 48 h and presented with an empty water bottle to induce appetitive behavior. The presentation of an empty water bottle to thirsty rats induced increased approaches to the bottle while they tried to drink. While water deprivation per se increased Fos-ir in the dorsal raphe and the locus coeruleus, the presentation of the bottle increased Fos-ir in the tuberomammillary nucleus and induced a further Fos-ir increase in the locus coeruleus. Other male rats were conditioned to amphetamine (1.5 mg/Kg i.p.) using a place preference task. Conditioned rats, but not rats injected with saline instead of amphetamine, showed a significant preference for amphetamine-paired room and increase in the number of Fos-ir in the tuberomammillary nucleus, orexin hypothalamic neurons and locus coeruleus. To evaluate the importance of the histaminergic neurons in the appetitive phase of these motivated behavior, we lesioned tuberomammillary nucleus using saporin conjugated to the hypocretin 2. The histaminergic neurons lesion blunted the appetitive phase in all motivated behaviors studied, without affecting general motor capacities. Taken together our results indicate that the histaminergic neurons become active at the onset of different motivated behaviors and they are key in the arousal that is essential in motivation. Other arousal nuclei may participate depending on the particular behavior.

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

Loyd DR, Murphy AZ (2007) Lesioning mu opioid receptor-containing neurons in the ventrolateral periaqueductal gray attenuates morphine analgesia in male but not female rats. Neuroscience 2007 Abstracts 921.4/NN15. Society for Neuroscience, San Diego, CA.

Summary: Chronic pain will affect four out of five persons at some point across the lifespan. While the opioid-based narcotic morphine is the most prevalent treatment for chronic pain in clinical settings, it is becoming increasingly clear that morphine produces a significantly greater degree of analgesia in males compared to females. In both somatic and visceral pain models, the ED50 for morphine is generally two-fold higher for females than for males. The midbrain periaqueductal gray (PAG) and its descending projections to the rostral ventromedial medulla (RVM) is the primary circuit for opioid-based analgesia. We have recently shown that the PAG-RVM pathway is sexually dimorphic both in its anatomical organization and in its activation during persistent pain. Interestingly, while female rats have a greater number of PAG neurons that project to the RVM, inflammatory pain activates these cells to a greater degree in males. Additionally, systemic morphine inhibits the pain-induced activation of PAG neurons in males, but not females. Sex differences in neuronal activity during pain and morphine analgesia are prominent in the ventrolateral PAG, a region containing a large population of mu opioid receptor-containing neurons. We have recently shown that females have significantly lower levels of mu opioid receptors (MOR) in this region, however it is not known whether sex differences in MOR expression contribute to our observed sex differences in morphine analgesia. To test the role of ventrolateral PAG MOR in morphine analgesia, the cytotoxin saporin conjugated to the MOR agonist dermorphin (Der-Sap) was injected into the ventrolateral PAG to site-specifically lesion MOR-containing neurons. Twenty-eight days later, rats received an intraplantar injection of CFA to induce persistent pain and twenty-four hours later morphine was administered systemically using a cumulative dosing paradigm (1.8 -18mg/kg). Lesions of PAG MOR-containing neurons resulted in a two-fold rightward shift in morphine ED50 values in male rats compared to controls. Interestingly, in females no difference was noted in morphine ED50 for Der-Sap treated females versus controls suggesting that the PAG is not a critical site for morphine analgesia in females. Der-Sap treatment had no significant impact on baseline paw withdrawal latencies or CFA-induced hyperalgesia. These results indicate that the PAG is a primary locus for systemic morphine analgesia in males only and suggests the necessity for the development of sex-specific treatments for persistent pain in females.

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

Pang K, Sinha SP, Jiao X, Servatius RJ (2007) Understanding the role of non-cholinergic medial septal neurons in learning and memory: Implications for disease- and aging-related impairments. Neuroscience 2007 Abstracts 932.22/WW17. Society for Neuroscience, San Diego, CA.

Summary: The medial septum-diagonal band of Broca (MS) has an important function in learning and memory. Furthermore, degeneration of the MS may contribute to cognitive impairments associated with Alzheimer’s disease and normal aging. Because the MS contains several types of neurons, the neuronal population(s) involved in learning and memory has been actively investigated. Animal studies have mainly focused on the cholinergic neurons that project to the hippocampus. Although complete lesions of the MS or fimbria-fornix transaction leads to spatial memory impairments, selective damage of cholinergic MS neurons produces no or a mild impairment in spatial memory, suggesting an important role of non-cholinergic neurons. Most of these non-cholinergic neurons are GABAergic. Previously, we used low concentrations of kainic acid to examine the importance of non-cholinergic MS neurons in spatial memory. However, a more selective toxin for GABAergic neurons would facilitate research, as it has done for the cholinergic system. In the present study, we use a new GABAergic immunotoxin that combines an antibody to the GABA transporter GAT1 with saporin. GAT1-saporin was administered into the medial septum of male Sprague Dawley rats. Our preliminary results show that GABAergic septohippocampal neurons as assessed by parvalbumin-immunoreactivity were virtually eliminated, while cholinergic neurons were spared in the medial septum. Current work is focused on further characterizing the cell populations affected by GAT1-saporin. Preliminary behavioral results demonstrate that GABA MS lesions did not impair spatial reference memory in the initial acquisition of a water maze task. However, a deficit was observed in reversal learning. Further testing in a procedure where the escape platform moves to a new location every day showed that rats treated with GAT1-saporin were mildly impaired in within-session learning of the new platform location. These preliminary results demonstrate that intraseptal GAT1-saporin is effective in eliminating at least some populations of GABAergic neurons in the MS. Furthermore, the preliminary behavioral results are consistent with our previous results demonstrating that damage of non-cholinergic MS neurons produces a very specific impairment on reversal learning. In summary, GAT1-saporin may be a useful tool to examine the function of GABA MS neurons in learning and memory and their contribution to cognitive impairments in disease and aging.

Related Products: GAT1-SAP (Cat. #IT-32)

ATS Poster of the Year Winner

Gompf HS, Fuller PM, Saper CB, Lu J (2007) Locus coeruleus (LC) is involved in sustaining arousal. Neuroscience 2007 Abstracts 736.3/UU16. Society for Neuroscience, San Diego, CA.

Summary: The locus coeruleus (LC) has traditionally been thought to be involved in arousal; however, lesions of the LC have minimal effects on basal sleep-wake behavior. We propose that the LC instead may be required to sustain arousal under conditions of environmental challenge. To test this hypothesis, we intraventricularly injected saline, or 0.25, 0.5, or 1µg anti-DBH-saporin (DBH-SAP selectively lesions the LC), and implanted EEG/EMG electrodes. On recording days, each animal was paired with a normal rat (social interaction) and presented with novel objects every hour for 5 hours from ZT 6 to ZT 11. We then repeated the same experiment for 2.5 hrs and immunostained tissue for Fos and TH or Fos and DBH. We also repeated the same experiment in rats with unilateral LC lesion by 6-OHDA. During 5 hr of stimulation with novel objects and social interaction (distracting stimuli, DS), controls or partial LC lesioned animals (0.25 µg DBH-SAP) spent 83 ± 8% and 92 ± 4% awake respectively (n = 3 and 4, p = 0.4) whereas animals with complete LC lesions (0.5 and 1 µg) spent significantly less time in wakefulness (59 ± 4% and 66 ± 5% respectively, n = 3 and 4, p = 0.0005). The reduction of wakefulness occurred primarily during the second 30 mins of each hour. Following DS exposure, Fos was highly expressed in the cerebral cortex in both LC lesioned groups and controls. Furthermore, we found a correlation (R2 = 0.79) between the remaining LC neurons and wakefulness under DS. Rats with loss of one LC showed no changes in wakefulness, and Fos was highly and symmetrically induced in the cerebral cortex. Our results suggest that the LC is specifically involved in sustaining arousal.

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

Martin MM, Carter LA, Jones JL, Winter SS, Wallace DG (2007) Organization of food protection behavior is differentially influenced by hippocampal and cortical cholinergic deafferentation. Neuroscience 2007 Abstracts 742.6/AAA9. Society for Neuroscience, San Diego, CA.

Summary: Previous work has suggested that rats use temporal information to organize their food protection behaviors. Studies have demonstrated different roles for hippocampal and cortical cholinergic function in processing of temporal information in standard interval timing procedures. The present study examined the role of hippocampal and cortical cholinergic function on the organization of food protection behavior. Long Evans female rats received either injections of 192 IgG-Saporin (SAP) or saline (SHAM) into the medial septum (MS) or nucleus basalis (NB). Subsequent to recovery, rats were placed into an enclosure and provided a hazelnut in the presence of an unoperated conspecific. All rats engaged in dodging or bracing behaviors to prevent the theft of the hazelnut. During a dodge, the rat places the food item in its mouth to use both fore- and hind-limbs to escape the approaching conspecific. In contrast, during a brace, the rat’s forelimbs maintain contact with the food item, and only the hind limbs are used to make shorter lateral movements. Only rats receiving sham lesions displayed a consistent transition from primarily engaging in dodging behavior to primarily engaging in bracing behavior during the consumption of the hazelnut. The MS SAP group displayed a disruption in their temporal organization of food protection behaviors. Although the NB SAP animals displayed impaired responding to the approaching conspecific (resulting in frequent thefts), their food protection behaviors tended to exhibit temporal organization. These results provide further evidence as to the role of the basal forebrain cholinergic system in temporal organization of behavior.

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

Wallace DG, Knapp SK, Silver JA, Martin MM, Winter SS (2007) Selective hippocampal cholinergic deafferentation disrupts exploratory trip organization. Neuroscience 2007 Abstracts 743.17/BBB11. Society for Neuroscience, San Diego, CA.

Summary: Rats organize their exploration of an environment around a central location or home base. Movements away from the home base are characterized as a series of slow progressions punctuated by stops. Subsequent to the last stop, the homeward segment is a single, rapid progression associated with a consistent temporal pacing of linear speeds. Observing these characteristics of exploratory behavior independent of environmental cue availability or familiarity has supported rats’ use of self-movement cues generated after departing the home base to estimate the distance and direction back to the home base. The current study investigated the effects of selective hippocampal cholinergic deafferentation on home base establishment and exploratory trip organization. Long Evans female rats either received injections of 192 IgG-Saporin (SAP) or saline (SHAM) into the medial septum. Subsequent to recovery, rats were placed on a large circular table with access to a refuge under complete dark conditions (infrared cameras and goggles were used to visualize the rat). Although all rats established a home base in the refuge, impairments in exploratory trip organization specific to the homeward segment were observed in SAP rats. Specifically, SAP rats displayed inconsistent temporal pacing of homeward segment linear speeds. These observations are consistent with a role for hippocampal cholinergic function in processing self-movement cues.

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

Young D, Howe WM, Martinez V, Bruno JP, Sarter M (2007) Neuronal mechanisms underlying the cognitive symptoms in a model of schizophrenia: prefrontal cholinergic inputs are necessary for attentional performance following repeated exposure to amphetamine. Neuroscience 2007 Abstracts 606.9/GG1. Society for Neuroscience, San Diego, CA.

Summary: The neuronal and cognitive effects of repeated exposure to amphetamine (AMPH) model important aspects of schizophrenia. Our prior results indicated that the attentional performance of AMPH-pretreated animals was maintained by abnormally high levels of prefrontal acetylcholine (ACh) release, and that the disruption of attentional performance by AMPH challenges was associated with a failure of the prefrontal cholinergic input system to respond to task onset (Kozak et al. 2007). The present experiment was designed to demonstrate that prefrontal cholinergic inputs are necessary for the (residual) attentional performance following repeated AMPH exposure. As removal of cortical cholinergic inputs per se disrupts attentional performance, we tested the hypothesis that limited prefrontal cholinergic deafferentation, which does not affect baseline attentional performance, prevents the establishment of normal performance following AMPH pretreatment. Rats were trained to perform a sustained attention task requiring the detection of visual signals and the discrimination between signal and non-signal events. Bilateral infusions of small concentrations and volumes of the immunotoxin 192 IgG-saporin into the medial prefrontal cortex did not affect the animals’ baseline performance. After re-establishing stable baseline performance, animals were pretreated with either saline or AMPH in accordance with an established, non-neurotoxic, escalating dosing regimen (1-10 mg/kg, twice daily over 40 days; Robinson et al. 1988). Animals were tested daily throughout the experiment. Following completion of the pretreatment regimen, the attentional performance of sham-lesioned controls recovered slowly over three weeks of continued training/testing. In contrast, performance recovery of deafferented, AMPH-pretreated animals was robustly attenuated and failed to reach pre-treatment levels. Collectively, these results indicate the necessary role of the prefrontal cholinergic input system in mediating the residual attentional performance of repeated AMPH. Therefore, pro-cholinergic treatments are predicted to benefit the attentional performance of schizophrenics. Repeated AMPH serves as a useful model to investigate the neuronal mechanisms underlying the cognitive symptoms of schizophrenia.

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

Ganapini V, Powers F, Kuper K, Taylor A, Fraley GS (2007) Galanin-like peptide stimulates feeding and sexual behavior via dopaminergic fibers within the medial preoptic area of adult male rats. Neuroscience 2007 Abstracts 626.14/VV17. Society for Neuroscience, San Diego, CA.

Summary: Galanin-like peptide (GALP) is a hypothalamic neuropeptide known to regulate both food intake and sexual behaviors in adult male rats. We have demonstrated that ICV GALP administration elicits a significant fos response within the mPOA; thus, we feel that GALP stimulates feeding and reproduction by actions within the mPOA. Recent data from our and other labs have led us to suspect that GALP effects on these behaviors are due to activation of tuberoinfundibular dopaminergic neurons that terminate within the mPOA. To test the hypothesis that GALP activates mPOA dopaminergic systems, we utilized an immunolesion technique to eliminate dopaminergic fiber input specific to the mPOA via a dopamine-transporter specific toxin (DATSAP, n = 8) and compared to control injections (SAP, n = 8). All animals were sexually experienced adult male Long Evans rats. We first tested their response to a sexually-primed female rat. DATSAP-treated male rats showed a significant (p <0.001) reduction in male sexual behavior compared to SAP controls. We found that elimination of dopamine fibers within the mPOA significantly (p < 0.001) eliminated all aspects of male sexual behavior under normal mating paradigms. Injections of GALP (5.0 nmol) significantly increased (p < 0.01) male sex behavior in SAP control male rats but GALP was unable to stimulate the expression of these behaviors in DATSAP-treated rats. ICV GALP significantly (p < 0.05) stimulated fos within the mPOA of SAP rats but not in DATSAP-treated male rats. There was no significant difference in 24 hr food intake between SAP and DATSAP rats. However, the orexigenic effect of ICV GALP was significantly (p < 0.001) attenuated in DATSAP-treated male rats compared to SAP controls. These data suggest that GALP activates feeding and sexual behaviors in male rats by stimulating dopaminergic neurons that terminate within the mPOA.

Related Products: Anti-DAT-SAP (Cat. #IT-25)

I’Anson H, Jethwa PH, Tanna GA, Pattinson LM, Ebling FJP (2007) Histaminergic regulation of energy homeostasis in the Siberian hamster. Neuroscience 2007 Abstracts 629.17/YY20. Society for Neuroscience, San Diego, CA.

Summary: We tested the hypothesis that posterior hypothalamic histaminergic (HA) activity regulates energy homeostasis in the Siberian hamster during long day (breeding season) photoperiods. Adult male Siberian hamsters were given bilateral injections of the retrogradely transported ribosomal toxin, saporin, conjugated to orexin-B receptor antibody (OXSAP, 200 nl, 92 ng/ul) into the posterior hypothalamus (PH) to selectively destroy HA neurons, the majority of which possess orexin-B receptors. Controls were injected with unconjugated saporin (sham). Metabolic rate (VO2 ml/kg0.75/h), ingestive behavior and locomotor activity were monitored using the comprehensive lab animal monitoring system (CLAMS, Columbus instruments). Body weight was significantly decreased by day 12 post-surgery in OXSAP compared with sham hamsters and remained significantly lower throughout the 5 month study, even though food intake was comparable between groups. At 3 months post-surgery, OXSAP food intake was significantly higher in the dark (p< 0.05) and significantly lower in the light phase (p<0.05), but not different overall between groups. In addition, the frequency of feeding bout tended to be lower during dark and light phases compared with sham hamsters (p=0.07). Lower body weight with no overall change in food intake suggests an increase in energy expenditure in the OXSAP hamsters. Consistent with this interpretation, locomotor activity in OXSAP hamsters tended to be higher during the dark phase (p=0.09), but not in the light phase. In addition, metabolic rate was significantly higher during the first two hours of the dark phase compared with sham hamsters (p<0.05), and tended to be higher during the entire dark phase (p=0.08). During a second CLAMS study (4 months post-surgery), metabolic rate was monitored following injection of an H3 receptor antagonist (thioperamide, 30 mg/kg, ip) as a probe to determine if any significant HA cell loss had occurred. Metabolic rate was significantly lower during the first 2 hours after thioperamide in sham hamsters, but not in OXSAP hamsters, suggesting that HA regulation of energy balance had been compromised by the OXSAP lesion. Immunohistochemical results confirmed 63-96% loss of HDC-immunoreactivity in magnocellular neurons of the posterior hypothalamus in the OXSAP group. These data support the hypothesis that posterior hypothalamic HA neuron activity modulates metabolic activity during the breeding season in the Siberian hamster, although it is likely that ablation of additional neuronal phenotypes which express orexin-B (e.g. MCH) may contribute to the observed metabolic effects.

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