Behavioral Effects of Cocaine--Metabolic and Neurochemical Approach. In: Ellinwood EH, Kilbey MM, editors. Cocaine and Other Stimulants. Boston: Springer US; 1977. pp. 229-40. [DOI: 10.1007/978-1-4684-3087-5_12]

Brain and plasma levels of cocaine and benzoylecgonine in lead-expose and cadmium-exposed rats following acute or chronic intraperitoneal administration of cocaine

Previous investigations of metal/cocaine interactions have shown that chronic oral exposure to inorganic lead or cadmium attenuates the psychoactive effects of acute or repeated administration of cocaine. The purpose of this investigation was to assess the possibility that such interactive effects may derive from metal-induced disturbances in cocaine pharmacokinetics, i.e., delivery of cocaine to critical biologic sites may be disrupted by metal contamination. In this study, adult male rats were exposed to purified diets containing 250 ppm lead acetate (Group Lead), 100 ppm cadmium chloride (Group Cadmium), or unadulterated laboratory chow (Group Control); n = 48/exposure condition. Following ad libitum access to their respective diets in the home cage for 45 days, half the animals from each exposure regimen received single daily IP injections of 5, 10, or 20 mg/kg cocaine HCl for a period of 7 days (n = 8/group). The remaining half the animals received repeated daily injections of saline during this pretreatment phase. On the day following pretreatment, animals previously receiving cocaine injections were administered a single cocaine test challenge at a dose equal to that received in pretreatment. Similarly, saline pretreatment animals received either 5, 10, or 20 mg/kg cocaine. The results of this investigation did not reveal reliable evidence of metal-related differences in brain levels of cocaine. Plasma cocaine and benzoylecgonine (BE) levels also were essentially the same for control and metal-exposed animals. The failure to show that lead or cadmium alters the disposition of cocaine in brain or plasma underscores the need to pursue alternative accounts of metal/cocaine interactions.

Withdrawal from continuous or intermittent cocaine: behavioral responsivity to 5-HT1 receptor agonists

Research on chronic cocaine administration indicates that both the dose and route of administration influences the effects of chronic cocaine. Rats were pretreated with 40 mg/kg/day cocaine for 14 days by either SC injections or osmotic minipumps. Rats were then withdrawn from the pretreatment regimen for 7 days and their behavior rated following injections of 5-hydroxytryptamine1A (5-HT1A) or 5-HT1B agonists. In Experiment 1, rats received 0- to 4.0-mg/kg IP injections of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a selective 5-HT1A receptor agonist. In Experiment 2, rats received 0- to 16.0-mg/kg IP injections of 7-trifluoromethyl-4(4-methyl-1-piperazinyl)- pyrrolo[1,2a]quinoxaline (CGS 12066B), a selective 5-HT1B receptor agonist. The results of Experiment 1 indicated that rats receiving cocaine via osmotic minipumps exhibited marked 5-HT1A receptor subsensitivity. In contrast, rats receiving daily cocaine injections sometimes demonstrated evidence of 5-HT1A supersensitivity and sometimes demonstrated evidence of 5-HT1A normosensitivity. The results of Experiment 2 indicated there were no consistent differences between the pretreatment groups in the behavioral response to CGS 12066B, although there were significant differences at single, isolated time points. Overall, the results indicate that, at least in the present behavioral paradigm, the effects of chronic cocaine administration are mediated by changes in 5-HT1A receptor sensitivity but not by changes in 5-HT1B receptor sensitivity.

Cocaine disposition in discrete regions of rat brain

It has been proposed that various effects of psychoactive drugs on the central nervous system may be related to the capacity of the drug to selectively concentrate in specific regions of the brain. In rat brain, cocaine effects on striatal and nucleus accumbens dopaminergic systems show quantitative differences. However, the disposition of cocaine in various brain regions has not been reported. In the present studies we examined the cocaine concentrations over time in serum and discrete brain regions of the rat after single intraperitoneal (i.p.) injection. At different time points (5, 10, 20, 30, 60, 120, and 240 min) after i.p. injection of cocaine hydrochloride (10 mg kg-1, free base) the rats were decapitated and cocaine in serum and various brain regions was quantitated by a specific gas liquid chromatographic method. There was large inter-individual variability in different rats at each time-point. The disposition pattern of cocaine in rats after i.p. administration was similar to that observed in humans after intranasal administration. Initial absorption rate was rapid and, on average, the peak levels of cocaine were achieved in 10 min. The cocaine levels remained relatively high over the next 50 min indicating continual absorption, and then declined with a rate such that the levels 4 h after cocaine administration were undetectable in most of the animals. The overall changes in cocaine levels in various brain regions paralleled the serum concentrations. The area under the cocaine concentration-time curve (AUC) revealed more than three-fold differences in cocaine accumulation in various brain regions. This unequal disposition of cocaine may be responsible in part for differential biochemical effects in different brain regions.

Intermittent and continuous cocaine administration: residual behavioral states during withdrawal

Rats were pretreated with 40 mg/kg/day cocaine for 14 days by either subcutaneous injections or osmotic minipumps. Rats were then withdrawn from the pretreatment regime for 1 or 7 days and given a 20-mg/kg IP cocaine challenge (day 1) or a 0-, 10-, 20-, or 40-mg/kg IP cocaine challenge (day 7). The results indicate that rats receiving intermittent, daily injections exhibited sensitization to the behavioral effects of a cocaine challenge on days 1 and 7 of withdrawal. In contrast, rats receiving continuous cocaine exhibited tolerance to the behavioral effects of a cocaine challenge on days 1 and 7 of withdrawal. The present results support and extend previous research that indicates that the route and temporal pattern of administration influences the effects of chronic cocaine. Furthermore, the present results indicate that the continuous infusion paradigm may represent an alternative animal model of some aspects of high-dose cocaine abuse, as compared to the typical procedure of single, or multiple, daily cocaine injections.

Recent Advances in Pharmacological Research on Alcohol

Alcohol dependence is a major public health problem. Studies have shown that a person dependent on alcohol often coabuses other substances, such as cocaine. Cocaine is a powerful stimulant whereas ethanol is generally considered to be a depressant, with some stimulating properties. The subjective effects of these two substances in a dependent individual may often appear to be more similar than they are different. Animals also self-administer both substances. Basically, although both substances have anesthetic properties and both act to functionally increase catecholaminergic function, especially that of dopamine, there are some differences in their actions. Both alcohol and cocaine have various effects on several neurotransmitters and systems, which ultimately interact to produce the feeling of well-being avidly sought by many individuals today. This drive often eventually produces a dependence which has associated social and medical consequences. It seems likely that the neurochemical changes that ensue following abuse of these substances underlie the phenomena of dependence, tolerance, and subsequent withdrawal. The apparent similarities and differences between these two substances will be reviewed in this chapter.

Comparison of sensitization to ambulation-increasing effects of cocaine and methamphetamine after repeated administration in mice

The effects of repeated (5 times) subcutaneous administration of cocaine (10, 20 or 40 mg kg-1) and methamphetamine (1, 2 or 4 mg kg-1) at 3-4 day intervals have been compared in mice placed individually into tilting activity cages. A progressive enhancement of the ambulation-increasing effect was noted for 3-4 h after each administration, indicating that sensitization occurred. This occurrence and the existence of an optimal dose producing sensitization were similar for both drugs. However, enhancement of the effect after cocaine progressed rapidly and maximum sensitization was observed earlier than after methamphetamine administration. Moreover, the higher doses of cocaine (40 mg kg-1) caused stereotypies concurrent with preconvulsive signs of short duration that were enhanced by serial administration. In contrast, methamphetamine caused a more progressive enhancement, but stereotypies with no preconvulsive signs were produced by the higher dose (4 mg kg-1). The respectively, effective doses for the development of enhancement suggested that cocaine was less potent than methamphetamine in producing sensitization. Cross-sensitization occurred between both drugs. Thus, sensitization to cocaine was distinct from that to methamphetamine due to differences in its rapidity, intensity, and the presence or absence of preconvulsive changes.

Stepwise detoxification from cocaine. A promising regimen

Cocaine dependence may not respond to behavioral and self-help treatment because of alterations in neurochemistry, particularly the catecholamine system. Thus, medical detoxification using a stepwise approach and several different therapeutic agents is often needed to assist the patient in achieving a cocaine-free state. An outpatient regimen includes regular clinic attendance, urine testing, education of patient and family, psychological evaluation, and a three- to four-week counseling program. Continued use of medication may be advisable for four to six months. Re-treatment is encouraged if relapse occurs.

Acute and chronic effects of the benzodiazepine receptor ligand FG 7142: proconvulsant properties and kindling

The effects of the acute and chronic administration of the beta-carboline benzodiazepine receptor ligand, FG 7142 were studied in mice. On acute administration FG 7142 (at doses between 10 and 40 mg kg-1) lowered seizure thresholds to infused pentylenetetrazol (PTZ) but showed an unusual dose-response curve in that higher doses had less effect. The duration of action was considerably longer than that of other beta-carbolines, such as ethyl-beta-carboline-3-carboxylate (beta CCE). During repeated administration, doses of FG 7142 which were initially proconvulsant subsequently produced generalized seizures on average in 60% of animals after 12 once daily treatments. This seemed to be a form of chemical kindling. The effects of different drug administration regimes were studied. Once daily dosage was shown to be the optimum for kindling production, and was therefore used for subsequent experiments. Kindling lasted for at least one month after 12 single once daily doses of 40 mg kg-1 (FG 7142). The administration of the benzodiazepine antagonist Ro 15-1788 concurrent with FG 7142 prevented kindling. When Ro 15-1788 was given to kindled animals along with a challenge dose of FG 7142, it prevented the expression of kindled seizures. These data show that kindling is mediated via the benzodiazepine receptor.