Carlezon Jr WA, Chartoff EH. Intracranial self-stimulation (ICSS) in rodents to study the neurobiology of motivation. Nat Prot 2: 2987-2995
ABSTRACT It has become increasingly important to assess mood states in laboratory animals. Tests that reflect reward, reduced ability to experience reward (anhedonia) and aversion (dysphoria) are in high demand because many psychiatric conditions that are currently intractable in humans (e.g., major depression, bipolar disorder, addiction) are characterized by dysregulated motivation. Intracranial self-stimulation (ICSS) can be utilized in rodents (rats, mice) to understand how pharmacological or molecular manipulations affect the function of brain reward systems. Although many different methodologies are possible, we will describe in this protocol the use of medial forebrain bundle (MFB) stimulation together with the 'curve-shift' variant of analysis. This combination is particularly powerful because it produces a highly reliable behavioral output that enables clear distinctions between the treatment effects on motivation and the treatment effects on the capability to perform the task.
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- "Surgical procedures for implanting electrodes in mice for ICSS studies were similar to those previously reported (Carlezon and Chartoff, 2007). Mice were anesthetized with isoflurane and received constant isoflurane delivery during surgical procedures. "
ABSTRACT: A growing body of evidence implicates endogenous cannabinoids as modulators of the mesolimbic dopamine system and motivated behavior. Paradoxically, the reinforcing effects of Δ9-tetrahydrocannabinol (THC), the primary psychoactive constituent of cannabis, have been difficult to detect in preclinical rodent models. In this study, we investigated the impact of THC and inhibitors of the endocannabinoid hydrolytic enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) on operant responding for electrical stimulation of the medial forebrain bundle (intracranial self-stimulation, ICSS), which is known to activate the mesolimbic dopamine system. These drugs were also tested in assays of operant responding for food reinforcement and spontaneous locomotor activity. THC and the MAGL inhibitor JZL184 attenuated operant responding for ICSS and food, and also reduced spontaneous locomotor activity. In contrast, the FAAH inhibitor PF-3845 was largely without effect in these assays. Consistent with previous studies showing that combined inhibition of FAAH and MAGL produces a substantially greater cannabimimetic profile than single enzyme inhibition, the dual FAAH-MAGL inhibitor SA-57 produced a similar magnitude of ICSS depression as that produced by THC. ICSS attenuation by JZL184 was associated with increased brain levels of 2-arachidonoylglycerol (2-AG), while peak effects of SA-57 were associated with increased levels of both N-arachidonoylethanolamine (anandamide; AEA) and 2-AG. The CB1 receptor antagonist rimonabant, but not the CB2 receptor antagonist SR144528, blocked the attenuating effects of THC, JZL184, and SA-57 on ICSS. Thus, THC, MAGL inhibition, and dual FAAH-MAGL inhibition not only reduce ICSS, but also decrease other reinforced and non-reinforced behaviors.Journal of Pharmacology and Experimental Therapeutics 11/2014; 352(2). DOI:10.1124/jpet.114.218677 · 3.86 Impact Factor
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- "The KOR agonists are well known to induce dysphoria and an anhedonic-like response in humans and mice (Potter et al., 2011; Ranganathan et al., 2012). For these studies, the anhedonia-like effects of sal A, RB-64, or U69593 were tested in C57BL/6J mice using the curve-shift method of ICSS (Carlezon and Chartoff, 2007). The mice responded in a frequency-dependent manner for BSR, as shown by the average baseline rate-frequency curves (Fig. 6A). "
ABSTRACT: The hypothesis that functionally selective GPCR agonists may have enhanced therapeutic benefits has revitalized interest for many GPCR targets. In particular, although κ-opioid receptor (KOR) agonists are analgesic with a low risk of dependence and abuse, their utility is limited by a propensity to induce sedation, motor incoordination, hallucinations and dysphoria-like states. Several labs have produced a body of work implying that G-protein biased KOR agonists might be analgesic with fewer side-effects. Although this has been an intriguing hypothesis, suitably KOR selective and G-protein biased agonists have not been available to test this idea. Here we provide data using a G-protein biased agonist RB-64 which suggests that KOR-mediated G protein signaling induces analgesia and aversion, whereas β-arrestin 2 signaling may be associated with motor incoordination. Additionally, unlike unbiased KOR agonists, the G protein-biased ligand RB 64 does not induce sedation and does not have anhedonia-like actions, suggesting that a mechanism other than G protein signaling mediates these effects. Our findings provide the first evidence with a highly selective and G-protein biased tool compound that many, but not all, of the negative side effects of KOR agonists can be minimized by creating G protein biased KOR agonists.Journal of Pharmacology and Experimental Therapeutics 10/2014; 352(1). DOI:10.1124/jpet.114.216820 · 3.86 Impact Factor
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- "In curveshift analysis, these data are then submitted to some form of regression analysis. Figure 6B shows linear regression through the ascending portions of the baseline and test frequency-rate curves, but both linear regression and different nonlinear regression equations have been used to fit ICSS data (Miliaressis et al., 1986; Coulombe and Miliaressis, 1987; Carlezon and Chartoff, 2007). Once the regression is established, it is used to calculate a measure of the lateral position of the curve along the X-axis. "
ABSTRACT: Intracranial self-stimulation (ICSS) is a behavioral procedure in which operant responding is maintained by pulses of electrical brain stimulation. In research to study abuse-related drug effects, ICSS relies on electrode placements that target the medial forebrain bundle at the level of the lateral hypothalamus, and experimental sessions manipulate frequency or amplitude of stimulation to engender a wide range of baseline response rates or response probabilities. Under these conditions, drug-induced increases in low rates/probabilities of responding maintained by low frequencies/amplitudes of stimulation are interpreted as an abuse-related effect. Conversely, drug-induced decreases in high rates/probabilities of responding maintained by high frequencies/amplitudes of stimulation can be interpreted as an abuse-limiting effect. Overall abuse potential can be inferred from the relative expression of abuse-related and abuse-limiting effects. The sensitivity and selectivity of ICSS to detect abuse potential of many classes of abused drugs is similar to the sensitivity and selectivity of drug self-administration procedures. Moreover, similar to progressive-ratio drug self-administration procedures, ICSS data can be used to rank the relative abuse potential of different drugs. Strengths of ICSS in comparison with drug self-administration include 1) potential for simultaneous evaluation of both abuse-related and abuse-limiting effects, 2) flexibility for use with various routes of drug administration or drug vehicles, 3) utility for studies in drug-naive subjects as well as in subjects with controlled levels of prior drug exposure, and 4) utility for studies of drug time course. Taken together, these considerations suggest that ICSS can make significant contributions to the practice of abuse potential testing.Pharmacological reviews 07/2014; 66(3):869-917. DOI:10.1124/pr.112.007419 · 18.55 Impact Factor