Discrete cues paired with naloxone-precipitated withdrawal from acute morphine dependence elicit conditioned withdrawal responses

Abstract

Acute bolus doses of morphine induce a state of acute opioid dependence as measured by naloxoneprecipitated withdrawal. Repeated morphine and precipitated withdrawal experience further enhances naloxone-induced withdrawal severity, in part due to direct neuroadaptation to repeated morphine, and in part due to conditioned associations of context and withdrawal experience. To determine whether a discrete tone/light conditioned stimulus (CS) could elicit conditioned withdrawal responses in acute dependence, rats trained on an FR-15 operant schedule for food reward received morphine (5.6 mg/kg) 4x at daily or weekly intervals, with each morphine injection followed at 4 hr by naloxone (1.0 mg/kg) and an operant session. The CS was presented to a Paired group after each naloxone injection. Separate control groups either experienced the CS at a different time of day or different day of the week than naloxone (Unpaired), received naloxone without any CS exposure (Paired-No CS) or received vehicle instead of naloxone prior to CS presentation (Nal-Naive). On the Test Day, all rats received vehicle prior to CS exposure. The CS alone reliably suppressed responding in Paired groups relative to control conditions with either daily or weekly intervals between conditioning sessions. Administration of morphine 4 hr prior to CS exposure on the Test Day was not necessary to observe conditioned withdrawal. Thus, conditioned withdrawal is reliably established to discrete cues associated with naloxone-precipitated withdrawal from acute infrequent (weekly) opioid exposure.

Precipitated and conditioned withdrawal in morphine-treated rats

“…The current study extends previous results (Goldberg and Schuster 1967; Azar et al, 2003; Amitai et al 2006) on conditioned withdrawal by assessing changes in body weight and directly observable withdrawal signs; many previous studies examined other withdrawal signs, including suppression of operant responding or place aversion conditioning (Goldberg and Schuster 1967; Azar et al, 2003; Amitai et al 2006). The current study also increases the number of treatment conditions examined because larger doses of morphine and naloxone are generally required to elicit weight loss and directly observable withdrawal signs (Schulteis et al 1998).…”

“…For example, morphine-dependent rats exhibit wet-dog shakes when placed in an environment where they previously experienced spontaneous withdrawal (Wikler and Pescor 1967). After lights or tones are paired with an opioid antagonist in morphine-treated rats, presentation of those stimuli alone disrupts food-maintained responding and produces ptosis and diarrhea -- signs of withdrawal (Schnur 1992; McNally and Akil 2001; Amitai et al 2006). Conditioned withdrawal can persist for long periods.…”

Relative potency of the opioid antagonists naloxone and 6-alpha-naloxol to precipitate withdrawal from acute morphine dependence varies with time post-antagonist

“…All drugs were prepared for injection in physiological saline, and all injections were made subcutaneously (SC) in a volume of 0.1 ml/100 g body weight. Morphine was administered at a dose of 5.6 mg/kg, selected from earlier work demonstrating effective induction of acute opioid dependence as measured by naloxone-precipitated withdrawal across a range of behavioral and somatic signs, including suppression of operant responding for food (Amitai et al, 2006; Azar et al, 2003; Liu and Schulteis, 2004; Schulteis et al, 2004, 2003; Zhang and Schulteis, 2008). Doses of all drugs are expressed as the salt.…”

Noradrenergic Synaptic Function in the Bed Nucleus of the Stria Terminalis Varies in Animal Models of Anxiety and Addiction

“…Next, we assayed animals that had experienced morphine withdrawal using a dependence paradigm that modeled the negative affect experienced by human addicts (Amitai et al, 2006;Koob, 2009;Schulteis et al, 1999). Once daily, we administered 10 mg/kg morphine s.c., followed by 1 mg/kg naloxone s.c. 4 h later (denoted MN), for a total of 3 days (SD n ¼ 27, L n ¼ 22).…”