targeted-toxins

Di Sebastiano AR, Yong-yow S, Coolen LM (2008) The role of orexin in sexual behavior and sexual reward of the male rat. Neuroscience 2008 Abstracts 97.4/UU18. Society for Neuroscience, Washington, DC.

Summary: The hypothalamic neuropeptide orexin has been demonstrated to play a role in reward related to drugs of abuse and is potentially involved in regulation of natural rewarding behaviors. Male sexual behavior has been shown to activate orexin neurons and this behavior is altered by administration of orexin receptor agonists or antagonists. However, the exact role of orexin in male sexual performance, sexual motivation and reward is currently unclear. Therefore, the goal of the current study was to test the hypothesis that orexin plays a critical role in sexual behavior, motivation and reward. First, using Fos as a marker for neural activation, we investigated activation of orexin neurons following different parameters of sexual behavior in sexually naïve and experienced male rats. It was demonstrated that orexin neurons in the lateral hypothalamic area (LHA) and in the dorsal medial hypothalamus/perifornical (PFA-DMH) region become activated with presentation of the female and there is no further increase in activation with other components of mating (15-30% in LHA; 65-80% in PFA-DMH). Next, we tested the functional role of orexin utilizing orexin-cell body specific lesions. Adult male rats underwent lesion or sham surgery using the targeted toxin orexin-saporin or blank-saporin respectively. Following two weeks recovery, sexual behavior was recorded over the course of four mating trials. During the first mating trial, males with complete lesions showed significantly shorter latencies to mount and intromit. This suggests that lesions facilitated sexual performance in naïve animals. This facilitation was attenuated by sexual experience as lesions did not affect any parameter of sexual behavior in experienced animals. Next, runway tests were conducted to determine motivation to run towards a potential partner over two conditioning trials. Lesions did not alter sexual motivation, as lesion and sham males all demonstrated increased speed to run towards an estrous female during the second trial. Finally, a conditioned place preference (CPP) paradigm was conducted as a measure of sexual reward. All groups formed a conditioned preference for the mating-paired chamber, indicating that lesions did not significantly disrupt sexual reward. Overall, these findings suggest that orexin does not play a critical role in male sexual performance, motivation, and reward, however may be involved in general arousal related to sexual behavior.

Related Products: Orexin-B-SAP (Cat. #IT-20), Blank-SAP (Cat. #IT-21)

Bee LA, Dickenson AH (2008) Descending facilitation from the brainstem determines behavioural and neuronal hypersensitivity following nerve injury and efficacy of pregabalin. Pain 140:209-223. doi: 10.1016/j.pain.2008.08.008

Summary: Rostral ventromedial medulla (RVM) facilitatory On cells are thought to be involved in the mechanisms that control chronic pain. Dermorphin-SAP (Cat. #IT-12, 3 pmol injected into the RVM of rats) was used to examine how mu-opioid receptor expressing facilitatory cells fit into this circuit. Saporin (Cat. #PR-01) was used as a control. The results show that activity in the RVM may influence the outcome of nerve injury.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12), Saporin (Cat. #PR-01)

Emanuel AJ, Dinh TT, Ritter S (2008) The ablation of hindbrain catecholamine neurons innervating medial hypothalamic nuclei abolishes glucoprivic feeding, but spares the orexigenic response to ghrelin. Neuroscience 2008 Abstracts 85.2/RR15. Society for Neuroscience, Washington, DC.

Summary: Ghrelin is an orexigenic peptide synthesized in the stomach and secreted during fasting. Receptors for ghrelin are present in the brain and direct injection of ghrelin into the brain evokes feeding. Nevertheless, Y. Date et. al. (2002) have claimed that gastric vagal afferent neurons are the major pathway conveying ghrelin’s signals for starvation and growth hormone secretion to the brain. Furthermore, this group (Date et. al., 2006), has reported that noradrenergic neurons transmit ghrelin’s orexigenic signals from the hindbrain to the hypothalamus. The latter assertion was based on the loss of ghrelin-induced feeding in rats injected into the arcuate nucleus (ARC) with anti-dopamine beta hydroxylase (DBH) conjugated to saporin (DSAP), which retrogradely destroys DBH-containing neurons. We previously showed that DSAP microinjection either into the hypothalamic paraventricular nucleus (PVH) or ARC abolished glucoprivic feeding. Since glucoregulatory responses include alterations of both feeding and growth hormone secretion, we reasoned that the same catecholamine neurons sensitive to glucoprivation may contribute to these responses following ghrelin. To investigate this issue further, we microinjected DSAP (n=7) or unconjugated saporin (SAP control, n=7) bilaterally into the PVH of Sprague-Dawley rats (approximately 400 g BW). Three weeks later, daytime tests for feeding responses to 2-deoxyglucose (2DG, 200 mg/kg, 4-hr test) and ghrelin (15 µg/kg, i.p., 2-hr test) were conducted. As expected, DSAP abolished 2DG-induced feeding. However, the response to ghrelin was not abolished in DSAP treated rats. In fact, feeding in response to ghrelin was significantly enhanced in DSAP-treated rats, compared to the control SAP group (p<0.05). These results confirm our prior findings relative to the role of catecholamine projections in glucoprivic responses, but they contradict the results previously reported by Date et. al. The difference between our injection sites (we injected DSAP into the PVH, and Date injected into the ARC) is not likely to account for the different results since injections of DSAP into either site eliminate DBH terminals throughout the medial hypothalamus and appear to lesion the same population of catecholamine neurons. Therefore, until more detailed analysis is conducted, we conclude that hindbrain catecholamine neurons are required for glucoprivic but not ghrelin-induced feeding.

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

Kalinchuk AV, McCarley RW, Stenberg D, Porkka-Heiskanen T, Basheer R (2008) The role of cholinergic basal forebrain neurons in adenosine-mediated homeostatic control of sleep: lessons from 192 IgG-saporin lesions. Neuroscience 157:238-253. doi: 10.1016/j.neuroscience.2008.08.040

Summary: The level of adenosine in the basal forebrain increases during sleep deprivation (SD). The cholinergic system of the basal forebrain is thought to be involved in the control of this process. 0.23 µg of 192-IgG-SAP (Cat. #IT-01) was injected into the horizontal diagonal band/ substantia innominata/ magnocellular preoptic nucleus, or 6 µg into the lateral ventricle of rats. The time course was dependent on the injection site, but eventually the SD-induced increase in adenosine was virtually eliminated.

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

Pedrino GR, Rosa DA, Korim WS, Cravo SL (2008) Renal sympathoinhibition induced by hypernatremia: Involvement of A1 noradrenergic neurons. Auton Neurosci 142(1-2):55-63. doi: 10.1016/j.autneu.2008.06.006

Summary: A1 noradrenergic neurons in the caudal ventrolateral medulla (CVLM) are thought to contribute to body fluid homeostasis and cardiovascular regulation. In order to examine the role these neurons play on inhibition of renal sympathetic nerve activity (RSNA) induced by hypertonic saline infusion, rats received 6.3 ng of anti-DBH-SAP (Cat. #IT-03) into the CVLM. Saporin (Cat. #PR-01) was used as a control. Animals treated with anti-DBH-SAP displayed lengthened duration of the pressor response and sustained RSNA.

Related Products: Anti-DBH-SAP (Cat. #IT-03), Saporin (Cat. #PR-01)

Bienkowski MS, Rinaman L (2008) Noradrenergic inputs to the paraventricular hypothalamus contribute to hypothalamic-pituitary-adrenal axis and central Fos activation in rats after acute systemic endotoxin exposure. Neuroscience 156(4):1093-1102. doi: 10.1016/j.neuroscience.2008.08.011

Summary: Noradrenergic (NA) neurons in the central nervous system are activated during the immune response to systemic lipopolysaccharide (LPS). The authors tested whether these neurons with axonal inputs to the paraventricular nucleus (PVN) were necessary for LPS-directed Fos expression and increase of plasma corticosterone. Rats received 44-ng bilateral injections of anti-DBH-SAP (Cat. #IT-03) into the medial PVN then were challenged with i.p. LPS. Lesioned animals had attenuated Fos activation and smaller than normal increases in plasma corticosterone.

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

Craig LA, Hong NS, Kopp J, McDonald RJ (2009) Selective lesion of medial septal cholinergic neurons followed by a mini-stroke impairs spatial learning in rats. Exp Brain Res 193(1):29-42. doi: 10.1007/s00221-008-1592-5

Summary: Recent work has suggested that reduced levels of acetylcholine, seen in Alzheimer’s disease patients, increases the susceptibility of hippocampal neurons to future challenges. Rats received two injections totaling 7.5 ng of 192-IgG-SAP (Cat. #IT-01) into the medial septum/vertical limb of the diagonal band of Broca. The vasoconstrictor endothelin-1 was used to create small localized strokes in the hippocampus of lesioned animals. The data suggest that loss of these hippocampal neurons compromises functional recovery from stroke.

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

Q: I am planning an experiment to investigate the effects of ablation of spinal NK-1r-expressing cells (using intrathecal injection of SSP-SAP, Cat. #IT-11). In the first part of the experiment I want to destroy the NK-1r-expressing cells before surgical modification. I am unsure how long after injection of SSP-SAP I should carry out the surgery. I was thinking of carrying out surgery at the two-week time point as in a 2007 Neuroscience paper by Wiley et al. Their immunocytochemistry showed a large reduction in staining at this time point. Any advice you could give me would be much appreciated.

A: Two weeks is probably fine. Generally cells begin to lose function at four days, but people wait longer because there is a clean-up by microglia/macrophage that removes the markers that people use for detection/demonstration of efficacy. Mantyh et al. were conservative with a 30-day wait for saporin clearance.

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

References

1. Wiley RG et al. Anti-nociceptive effects of selectively destroying substance P receptor-expressing dorsal horn neurons using [Sar(9),Met(O(2))(11)]-substance P-saporin: Behavioral and anatomical analyses. Neuroscience 146:1333-1345, 2007.
2. Mantyh PW et al. Inhibition of hyperalgesia by ablation of lamina I spinal neurons expressing the substance P receptor. Science 278:275-279, 1997.

Likhtik E (2008) Featured Article: Selective lesions of amygdala intercalated neurons using the Dermorphin-SAP immunotoxin reveal their role in conditioned fear. Targeting Trends 9(4)

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12), Blank-SAP (Cat. #IT-21)

Read the featured article in Targeting Trends.

See Also:

• Likhtik E et al. Amygdala intercalated neurons are required for expression of fear extinction. Nature 454(7204):642-645, 2008.

Murillo-Rodriguez E, Liu M, Blanco-Centurion C, Shiromani PJ (2008) Effects of hypocretin (orexin) neuronal loss on sleep and extracellular adenosine levels in the rat basal forebrain. Eur J Neurosci 28(6):1191-1198. doi: 10.1111/j.1460-9568.2008.06424.x

Summary: Adenosine levels in the basal forebrain are thought to regulate the waxing and waning of sleep drive. Rats received bilateral 100-ng injections of orexin-SAP (Cat. #IT-20) into the lateral hypothalamus – resulting in a 94% loss of orexin-containing neurons. Lesioned animals displayed several changes in sleep characteristics, but no increase of adenosine levels after sleep deprivation. The results indicate that sleep changes due to orexin-SAP lesioning occur independently of adenosine levels.

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