Ye J-H, Fu R, He W (2017) The rostromedial tegmental nucleus and alcohol addiction. Oncotarget 8:18624-18625.. doi: 10.18632/oncotarget.15822

Summary: The authors discuss their work with Dermorphin-SAP (Cat. #IT-12) and their demonstration that damage of RMTg MOR-expressing GABAergic neurons by Dermorphin-SAP increased the intake and preference for alcohol, boosted the expression and slowed down the extinction of alcohol conditioned place preference, and increased locomotion. Microinjection of DS into the RMTg substantially reduced the number of RMTg cells. Importantly, the rats that received DS injection elevated their alcohol intake and preference compared to those that received an injection of Blank-SAP (Cat. #IT-21), which did not cause neuronal damage.

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

Fu R, Chen X, Zuo W, Li J, Kang S, Zhou L, Siegel A, Bekker A, Ye J (2016) Ablation of μ opioid receptor-expressing GABA neurons in rostromedial tegmental nucleus increases ethanol consumption and regulates ethanol-related behaviors. Neuropharmacology 107:58-67. doi: 10.1016/j.neuropharm.2016.02.027

Summary: In this work the authors investigated cellular mechanisms underlying the aversive effects of alcohol that limit its intake. Previous work has linked synaptic inhibition of dopamine neurons in the ventral tegmental area to this aversion. Rats conditioned to ingest ethanol received bilateral injections totaling 3 pmol of Dermorphin-SAP (Cat. #IT-12) into the rostromedial tegemental nucleus (RTMg). Blank-SAP (Cat. #IT-21) was used as a control. Lesioned animals displayed significantly increased preference for, and intake of ethanol, while showing no change in the desire for sucrose. The results indicate that mu opioid expressing GABAergic neurons in the RTMg are highly involved in the regulation of ethanol consumption.

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

Horner KA, Murray R, Logan Merce MC (2016) Featured Article: Striatal patch compartment lesions reduce cocaine-induced repetitive behaviors. Targeting Trends 17(1)

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

Read the featured article in Targeting Trends.

See Also:

• Horner KA et al. Ablation of the patch compartment reduces cocaine-induced stereotypy. Neuroscience 2015 Abstracts 506.23/M12, 2015. Society for Neuroscience, Chicago IL

Harasawa I, Johansen J, Fields H, Porreca F, Meng I (2016) Alterations in the rostral ventromedial medulla after the selective ablation of μ-opioid receptor expressing neurons. Pain 157:166-173. doi: 10.1097/j.pain.0000000000000344

Summary: The rostral ventromedial medulla (RVM) has both excitatory and inhibitory control over nociceptive neurons in the medullary dorsal horn and spinal cord. Previous work has demonstrated that elimination of mu-opioid receptor-expressing neurons in the RVM reduces stress and injury-induced behavioral hypersensitivity, but the effect of losing these cells on the descending inhibitory system has not been examined. The authors administered 1.2 pmol of Dermorphin-SAP (Cat. #IT-12) to each side of the RVM of rats. Saporin (Cat. #PR-01) was used as a control. Characterization of RVM neurons in lesioned animals showed a reduction in on- and off-cells, but no change in the number of neutral cells. These data indicate that mu-opioid receptor-expressing cells in the RVM are not needed for analgesia produced by activation of RVM neurons.

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

Palomares E, Hernandez Perez O, Crespo Ramirez M, Aguilar Roblero R, Fuxe K, Perez de la Mora M (2015) Selective ablation of the intercalated neurons of the amygdala increased the anxiety-like behavior in the Elevated Plus Maze. Neuroscience 2015 Abstracts 694.14/N4. Society for Neuroscience, Chicago IL.

Summary: The intercalated (ITC) islands of the amygdala are clusters of inhibitory neurons that surround the basolateral complex (BLA) and contain a dense population of dopamine D1 and μ-opioid receptors. Lateral ITC (lITC) islands provide feed-forward inhibition to the BLA, whereas medial ITC (mITC) islands form an inhibitory interface between the BLA and central nucleus (CeA), the main output region of the amygdala. Previous studies have shown that ITC neurons play a role in fear extinction. However the functional role of the ITC islands in the un-conditioned anxiety has not been studied. To elucidate the involvement of the ITC islands in the anxiety-like behavior in the Elevated Plus Maze, we bilaterally infused the toxin saporin conjugate with the agonist of the μ-opioid receptors, dermorphine, (SAP-DER; 0.75pmol/0.250µl/lado) in closed proximity to the mITC islands to specifically ablate the neurons of the ITC islands. Behaviorally, SAP-DER injections significantly increased the time that the rats spent in the open arm of the maze as compared with their lesion control group. No effects on locomotion in the open-field test were found. These results suggest that ablate of the ITC neurons results in anxiogenic effects and support ITC neurons play an important role in mediate anxiolytic responses.

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

Horner KA, Logan M, Murray RC (2015) Ablation of the patch compartment reduces cocaine-induced stereotypy. Neuroscience 2015 Abstracts 506.23/M12. Society for Neuroscience, Chicago IL.

Summary: Repeated exposure to cocaine (COC) induces stereotypy, which is characterized as inflexible, repetitive behavior. Enhanced relative activation of the patch compartment of the striatum has been shown to positively correlate with the emergence of stereotypy following repeated COC treatment, suggesting that stereotypy may be related to preferential activation of this region. However, the specific contribution of the patch compartment to COC-induced stereotypy following repeated exposure is unknown. To elucidate the involvement of the patch compartment to the development of stereotypy in response to repeated COC exposure, we determined if destruction of this sub-region altered COC-induced behaviors. Animals were bilaterally infused in the striatum with the neurotoxin dermorphin-saporin (DERM-SAP; 17 ng/[[Unsupported Character – Symbol Font ]]l) to ablate the neurons of the patch compartment and allowed to recover for eight days. The animals were given daily injections of COC (25 mg/kg) or saline for one week, followed by a weeklong drug-free period. Animals were then given a challenge dose of COC, placed in activity chambers, observed for 2h and sacrificed. DERM-SAP pretreatment reduced the number of mu-labeled patches in the striatum. DERM-SAP pretreatment significantly reduced the intensity and spatial immobility of COC-induced stereotypy. In support of this observation, increased locomotor activity was seen in DERM-SAP pretreated, COC-treated animals. DERM-SAP pretreatment attenuated COC-induced c-Fos expression in the patch compartment, while enhancing COC-induced c-Fos expression in the matrix compartment. These data indicate that the patch compartment is necessary for repetitive behavior and suggests that alterations in activity in the patch vs matrix compartments may contribute to this phenomenon.

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

ATS Poster of the Year Winner. Read the featured article in Targeting Trends.

Murray R, Logan M, Horner K (2015) Striatal patch compartment lesions reduce stereotypy following repeated cocaine administration. Brain Res 1618:286-298. doi: 10.1016/j.brainres.2015.06.012

Summary: Stereotypy is defined as abnormally repetitive motor movements accompanied by an inability to initiate normal adaptive responses. Psychostimulants such as cocaine will often produce these movements. It is thought that stereotypy is related to activation of the patch compartment of the striatum. In order to better understand the function of the patch compartment in stereotypy due to repeated exposure to cocaine, the authors administered bilateral injections of Dermorphin-SAP (Cat. #IT-12) into the rostral striatum. Saporin (Cat. #PR-01) was used as a control.

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

Navratilova E, Xie J, Meske D, Qu C, Morimura K, Okun A, Arakawa N, Ossipov M, Fields H, Porreca F (2015) Endogenous opioid activity in the anterior cingulate cortex is required for relief of pain. J Neurosci 35:7264-7271. doi: 10.1523/JNEUROSCI.3862-14.2015

Summary: There are a number of neuronal circuits involved in the processing of pain, including those that control somatosensory, affective, and cognitive aspects of pain perception. Opioid signaling in the anterior cingulate cortex (ACC) plays a part in pain modulation – this area has also been implicated in the encoding of pain aversiveness. In order to examine the neuronal mechanisms of pain relief and the following reward, the authors of this paper administered 48 ng of Dermorphin-SAP (Cat. #IT-12) into the rostral ACC of rats. Saporin (Cat. #PR-01) was used as a control. The results illuminate the opioid pathway during pain treatment, and the dependence of nucleus accumbens dopaminergic transmission on upstream ACC opioid circuits during pain processing.

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

Cetas J, McFarlane R, Kronfeld K, Smitasin P, Liu J, Raskin J (2015) Brainstem opioidergic system is involved in early response to experimental SAH. Transl Stroke Res 6:140-147. doi: 10.1007/s12975-014-0378-2

Objective: To determine the cause of poor long-term outcomes after Subarachnoid hemorrhage (SAH).

Summary: Failure of the RVM μ-opioid receptor cells to initiate the compensatory CBF response sets the stage for acute and delayed ischemic injury following SAH.

Usage: To lesion medullary neurons expressing the μ-opioid receptor, Dermorphin–SAP was microinjected as a bilateral dose of 0.5 pmol in 500 nL per side (1 pmol in 1 μL total dose and injection volume). Blank–SAP or vehicle was injected in equal volumes and dose as controls.

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

Fu R, Chen X, Zho W, Li J, Ye J-H (2014) Selective ablation of mu opioid receptor expressing gaba neurons in the rostromedial tegmental nucleus promotes ethanol intake. Neuroscience 2014 Abstracts 267.30. Society for Neuroscience, Washington, DC.

Summary: BACKGROUND AND PURPOSE The cellular mechanisms underlying the aversive effect of ethanol that limits its intake are not well understood, although recent evidence has linked aversion with synaptic inhibition of dopamine neurons in the ventral tegmental area. Emerging evidence indicates that the rostromedial tegmental nucleus (RMTg), a newly defined midbrain structure exerts a major GABAergic inhibitory control over midbrain dopamine neurons and encodes aversive stimuli. The RMTg contains mostly GABAergic neurons and with dense μ-opioid receptor (MOR) immunoreactivity. However, the role of RMTg in the regulation of ethanol intake has not been well investigated. EXPERIMENTAL APPROACH We compared voluntary ethanol intake and locomotion in rats with intra-RMTg infusion of dermorphin-saporin or blank saporin. Dermorphin-saporin is a neurotoxin, which could selectively lesion MOR-expressing neurons. We measured ethanol intake in rats given intermittent access to ethanol (20% vol/vol) using a two bottle choice paradigm. We euthanized the rats, dissected their brains and analyzed the glutamic acid decarboxylase67 (GAD67) and MOR protein expression and immunoreactivity immediately following the behavioral test. KEY RESULTS In rats that received intra-RMTg injection of dermorphin-saporin, we observed a robust increase in the intake of and the preference to ethanol, and in the locomotor activity; but a significantly reduced GAD67 and MOR protein expression, as well as a massive loss of neurons with GAD67 and MOR immunoreactivity within the RMTg. We observed no such changes in rats that received injection of blank saporin or saline. Together, These findings indicate that MOR-expressing GABA neurons in the RMTg play a crucial role in the regulation of ethanol consumption, implicating the dysfunction of these neurons likely play a critical role in the pathogenesis of alcoholism, and that these neurons should represent an appropriate target for the development of therapeutic strategies against alcohol use disorders.

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