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Operant self-administration of ethanol in infant rats. Physiol Behav 2015; 148:87-99. [DOI: 10.1016/j.physbeh.2014.08.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 08/06/2014] [Accepted: 08/25/2014] [Indexed: 11/19/2022]
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Miranda-Morales RS, Molina JC, Spear NE, Abate P. Participation of the endogenous opioid system in the acquisition of a prenatal ethanol-related memory: effects on neonatal and preweanling responsiveness to ethanol. Physiol Behav 2010; 101:153-60. [PMID: 20451537 DOI: 10.1016/j.physbeh.2010.04.033] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2009] [Revised: 04/22/2010] [Accepted: 04/28/2010] [Indexed: 10/19/2022]
Abstract
The present study tested the involvement of the opioid system in the acquisition and expression of prenatal ethanol-related memories. We evaluated how this prenatal experience modulates ethanol self-administration in newborn rats, and preweanling's ingestion of the drug. During Gestational Days (GDs) 17-20, four groups of dams were treated with ethanol (2 g/kg) or water, followed immediately by naloxone (10 mg/kg) or saline administration. A fifth group received a similar dose of naloxone 20min before ethanol administration. On PD 1, pups were tested on an operant learning procedure to obtain milk or 3% ethanol. One hour later, an extinction session was performed. At Postnatal Days (PDs) 14 and 15, preweanlings representing each prenatal treatment were evaluated in an intake test with infusions of 5% ethanol or water. Prior to the intake test on PD14, preweanlings were administered naloxone (1 mg/kg), saline or remained untreated. In both tests, animals representative of both genders were utilized. One-day-old pups rapidly learned the operant behavior to gain access to milk. In contrast, only pups prenatally treated with ethanol (administered immediately before naloxone or saline injection) increased operant responding to gain access to ethanol. On an intake test at PDs 14 and 15, those animals prenatally exposed to naloxone 20 min before ethanol administration consumed significantly lower ethanol levels than the remaining prenatal ethanol groups. Postnatal treatment with naloxone diminished intake of all solutions at PD14. These results suggest that prenatal ethanol exposure facilitates neonatal operant learning reinforced by intraoral administration of ethanol and increases ethanol consumption during PDs 14-15. The endogenous opioid system apparently is involved in the acquisition of prenatal ethanol memories, which can modulate the reinforcing attributes of the drug in neonatal and preweanling rats.
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Kozlov AP, Nizhnikov ME, Varlinskaya EI, Spear NE. Pharmacological effects of ethanol on ingestive behavior of the preweanling rat. Behav Brain Res 2009; 205:162-74. [PMID: 19549546 PMCID: PMC2753683 DOI: 10.1016/j.bbr.2009.06.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 06/09/2009] [Accepted: 06/15/2009] [Indexed: 01/03/2023]
Abstract
The present study was designed to test the hypothesis that sensitivity of ingestive behavior of infant rat to the pharmacological effects of ethanol changes between postnatal (P) days 9 and 12. The intake of 0.1% saccharin and water, general motor activity, and myoclonic twitching activity were assessed following administration of three doses of ethanol (0, 0.25, and 0.5 g/kg) while fluids were free available to the animals. The 0.5 g/kg dose of ethanol attenuated saccharin intake in P9 pups and enhanced saccharin intake in P12 rats. On P12 some sex-related differences emerged at 0.5 g/kg of ethanol, with saccharin intake being higher in females than in their male counterparts. Taste reactivity probe revealed that 0.5 g/kg of ethanol increased taste responsiveness to saccharin on P12 but only to infusions presented at a high rate. The results of the present study indicate that ontogenetic changes in sensitivity to the effects of ethanol on ingestive behavior occur during the second postnatal week, with P9 animals being more sensitive to the inhibitory (sedative) effects on saccharin intake and P12 rats being more sensitive to the stimulatory effects of ethanol. We suggest that acute ethanol enhanced saccharin intake via sensitization of oral response to appetitive taste stimulation.
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Affiliation(s)
- Andrey P Kozlov
- Center for Development & Behavioral Neuroscience, Department of Psychology, Binghamton University, Binghamton, NY 13902-6000, United States
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March SM, Abate P, Spear NE, Molina JC. Fetal exposure to moderate ethanol doses: heightened operant responsiveness elicited by ethanol-related reinforcers. Alcohol Clin Exp Res 2009; 33:1981-93. [PMID: 19719792 PMCID: PMC3085171 DOI: 10.1111/j.1530-0277.2009.01037.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Prenatal exposure to moderate ethanol doses during late gestation modifies postnatal ethanol palatability and ingestion. The use of Pavlovian associative procedures has indicated that these prenatal experiences broaden the range of ethanol doses capable of supporting appetitive conditioning. Recently, a novel operant technique aimed at analyzing neonatal predisposition to gain access to ethanol has been developed. Experiment 1 tested the operant conditioning technique for developing rats described by Arias and colleagues (2007) and Bordner and colleagues (2008). In Experiment 2, we analyzed changes in the disposition to gain access to ethanol as a result of moderate prenatal exposure to the drug. METHODS In Experiment 1, newborn pups were intraorally cannulated and placed in a supine position that allowed access to a touch-sensitive sensor. Paired pups received an intraoral administration of a given reinforcer (milk or quinine) contingent upon physical contact with the sensor. Yoked controls received similar reinforcers only when Paired pups activated the circuit. In Experiment 2, natural reinforcers (water or milk) as well as ethanol (3% or 6% v/v) or an ethanol-related reinforcer (sucrose compounded with quinine) were tested. In this experiment, pups had been exposed to water or ethanol (1 or 2 g/kg) during gestational days 17 to 20. RESULTS Experiment 1 confirmed previous results showing that 1-day-old pups rapidly learn an operant task to gain access to milk, but not to gain access to a bitter tastant. Experiment 2 showed that water and milk were highly reinforcing across prenatal treatments. Furthermore, general activity during training was not affected by prenatal exposure to ethanol. Most importantly, prenatal ethanol exposure facilitated conditioning when the reinforcer was 3% v/v ethanol or a psychophysical equivalent of ethanol's gustatory properties (sucrose-quinine). CONCLUSIONS The present results suggest that late prenatal experience with ethanol changes the predisposition of the newborn to gain access to ethanol-related stimuli. In conjunction with prior literature, this study emphasizes the fact that intrauterine experience with ethanol not only augments ethanol's palatability and ingestion, but also facilitates the acquisition of response-stimulus associations where the drug acts as an intraoral reinforcer.
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Affiliation(s)
- Samanta M. March
- Instituto de Investigación Médica M. y M. Ferreyra (INIMEC – CONICET), Córdoba, Argentina
- Facultad de Psicología, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Paula Abate
- Instituto de Investigación Médica M. y M. Ferreyra (INIMEC – CONICET), Córdoba, Argentina
- Facultad de Psicología, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Norman E. Spear
- Center for Developmental Psychobiology, Binghamton University, Binghamton, NY, USA
| | - Juan Carlos Molina
- Instituto de Investigación Médica M. y M. Ferreyra (INIMEC – CONICET), Córdoba, Argentina
- Center for Developmental Psychobiology, Binghamton University, Binghamton, NY, USA
- Facultad de Psicología, Universidad Nacional de Córdoba, Córdoba, Argentina
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Pautassi RM, Nizhnikov ME, Spear NE. Assessing appetitive, aversive, and negative ethanol-mediated reinforcement through an immature rat model. Neurosci Biobehav Rev 2009; 33:953-74. [PMID: 19428502 PMCID: PMC2693872 DOI: 10.1016/j.neubiorev.2009.03.008] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Revised: 03/13/2009] [Accepted: 03/13/2009] [Indexed: 11/25/2022]
Abstract
The motivational effects of drugs play a key role during the transition from casual use to abuse and dependence. Ethanol reinforcement has been successfully studied through Pavlovian and operant conditioning in adult rats and mice genetically selected for their ready acceptance of ethanol. Another model for studying ethanol reinforcement is the immature (preweanling) rat, which consumes ethanol and exhibits the capacity to process tactile, odor and taste cues and transfer information between different sensorial modalities. This review describes the motivational effects of ethanol in preweanling, heterogeneous non-selected rats. Preweanlings exhibit ethanol-mediated conditioned taste avoidance and conditioned place aversion. Ethanol's appetitive effects, however, are evident when using first- and second-order conditioning and operant procedures. Ethanol also devalues the motivational representation of aversive stimuli, suggesting early negative reinforcement. It seems that preweanlings are highly sensitive not only to the aversive motivational effects of ethanol but also to its positive and negative (anti-anxiety) reinforcement potential. The review underscores the advantages of using a developing rat to evaluate alcohol's motivational effects.
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Affiliation(s)
- Ricardo M Pautassi
- Center for Development and Behavioral Neuroscience, State University of New York at Binghamton, Binghamton, NY 13902-6000, USA.
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Kozlov AP, Varlinskaya EI, Spear NE. Ethanol, saccharin, and quinine: early ontogeny of taste responsiveness and intake. Alcohol Clin Exp Res 2007; 32:294-305. [PMID: 18162068 DOI: 10.1111/j.1530-0277.2007.00581.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Rat pups demonstrate high levels of immediate acceptance of ethanol during the first 2 weeks of postnatal life. Given that the taste of ethanol is most likely perceived by infant rats as a combination of sweet and bitter, high intake of ethanol early in ontogeny may be associated with age-related enhanced responsiveness to the sweet component of ethanol taste, as well as with ontogenetic decreases in sensitivity to its bitter component. Therefore, the present study compared responsiveness to ethanol and solutions with bitter (quinine) and sweet (saccharin) taste in terms of intake and palatability across the first 2 weeks of postnatal life. METHODS Characteristic patterns of responsiveness to 10% (v/v) ethanol, 0.1% saccharin, 0.2% quinine, and water in terms of taste reactivity and fluid intake were assessed in rat pups tested on postnatal day (P) 4, 9, or 12 using a new technique of on-line monitoring of fluid flow through a two-channel intraoral cannula. Taste reactivity included analysis of ingestive and aversive responses following six intraoral infusions of the test fluids. This taste reactivity probe was followed by the intake test, in which animals were allowed to voluntarily ingest fluids from an intraoral cannula. RESULTS Pups of all ages showed more appetitive responses to saccharin and ethanol than to water or quinine. No age-related differences were apparent in taste responsiveness to saccharin and ethanol. However, the age-related pattern of ethanol intake drastically differed from that of saccharin. Intake of saccharin increased from P4 to P9 and decreased substantially by P12, whereas intake of ethanol gradually increased from P4 to P12. Intake of ethanol was significantly lower than intake of saccharin on P9, whereas P12 pups took in more ethanol than saccharin. CONCLUSION The findings of the present study indicate ontogenetic dissociations between taste reactivity to ethanol and saccharin and intake of these solutions, and suggest that high acceptance of ethanol early in ontogeny may not be associated with its orosensory properties but rather with the pharmacological effects of ethanol.
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Affiliation(s)
- Andrey P Kozlov
- Center for Developmental Psychobiology, Department of Psychology, Binghamton University, Binghamton, New York 13902-6000, USA
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Tzschentke TM. Measuring reward with the conditioned place preference (CPP) paradigm: update of the last decade. Addict Biol 2007; 12:227-462. [PMID: 17678505 DOI: 10.1111/j.1369-1600.2007.00070.x] [Citation(s) in RCA: 1006] [Impact Index Per Article: 59.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Conditioned place preference (CPP) continues to be one of the most popular models to study the motivational effects of drugs and non-drug treatments in experimental animals. This is obvious from a steady year-to-year increase in the number of publications reporting the use this model. Since the compilation of the preceding review in 1998, more than 1000 new studies using place conditioning have been published, and the aim of the present review is to provide an overview of these recent publications. There are a number of trends and developments that are obvious in the literature of the last decade. First, as more and more knockout and transgenic animals become available, place conditioning is increasingly used to assess the motivational effects of drugs or non-drug rewards in genetically modified animals. Second, there is a still small but growing literature on the use of place conditioning to study the motivational aspects of pain, a field of pre-clinical research that has so far received little attention, because of the lack of appropriate animal models. Third, place conditioning continues to be widely used to study tolerance and sensitization to the rewarding effects of drugs induced by pre-treatment regimens. Fourth, extinction/reinstatement procedures in place conditioning are becoming increasingly popular. This interesting approach is thought to model certain aspects of relapse to addictive behavior and has previously almost exclusively been studied in drug self-administration paradigms. It has now also become established in the place conditioning literature and provides an additional and technically easy approach to this important phenomenon. The enormous number of studies to be covered in this review prevented in-depth discussion of many methodological, pharmacological or neurobiological aspects; to a large extent, the presentation of data had to be limited to a short and condensed summary of the most relevant findings.
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Affiliation(s)
- Thomas M Tzschentke
- Grünenthal GmbH, Preclinical Research and Development, Department of Pharmacology, Aachen, Germany.
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Sanders S, Spear NE. Ethanol acceptance is high during early infancy and becomes still higher after previous ethanol ingestion. Alcohol Clin Exp Res 2007; 31:1148-58. [PMID: 17451398 DOI: 10.1111/j.1530-0277.2007.00400.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
BACKGROUND Infant (preweanling) rats readily accept ethanol without initiation procedures. During their second and third postnatal weeks, rats ingest large quantities of even high concentrations of ethanol. The present study tested the consequences of still earlier exposure to ethanol differing in concentration, mode of administration, and contextual circumstances. METHODS Every 48 hours from postnatal day 2 (P2) to P10, pups were given access to 0, 5, 15, or 25% ethanol through an independent feeding procedure (consumption off the floor; COF) or by intragastric (i.g.) administration. The amount of ethanol consumed was matched for the 2 modes of ethanol delivery. On P12 pups were tested for intake of 15% ethanol through an intraoral infusion test or COF. RESULTS Beginning on P6, pups ingested more ethanol solution than water, and by P8 and P10 they ingested large quantities of ethanol--1.5 to 2.0 g/kg ethanol from 15 or 25% ethanol solution within a 10-minute period. This early experience with ingestion of ethanol increased subsequent ethanol intake on P12, particularly when concentration and mode of ingestion were the same as before. CONCLUSIONS Intake on P12 was increased by prior exposure to ethanol intragastrically as well as by the conventional oral route, suggesting pharmacological effects of prior ethanol exposure. Yet, the apparently greater influence of prior exposure by the oral route and the influence of prior ethanol concentration also implicate the importance of ethanol's chemosensory attributes for effects of prior ethanol exposure. The equivalent g/kg intake of ethanol in 15 or 25% solutions during the early part of the second postnatal week suggests that regulation of ethanol intake at P8 and P10 is similar to that observed previously in adults. Change in aspects of ethanol ingestion at about P6 may reflect the shift in function of the GABA system at about this age.
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MESH Headings
- Administration, Oral
- Age Factors
- Alcohol Drinking/psychology
- Alcoholic Intoxication/etiology
- Animals
- Animals, Newborn/growth & development
- Animals, Newborn/physiology
- Behavior, Animal/drug effects
- Behavior, Animal/physiology
- Body Weight/drug effects
- Body Weight/physiology
- Brain/drug effects
- Brain/physiology
- Conditioning, Operant/drug effects
- Conditioning, Operant/physiology
- Discrimination, Psychological/physiology
- Dose-Response Relationship, Drug
- Drinking/drug effects
- Drinking/physiology
- Ethanol/administration & dosage
- Ethanol/pharmacology
- Infusion Pumps
- Rats
- Rats, Sprague-Dawley
- Self Administration/statistics & numerical data
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Affiliation(s)
- Sarah Sanders
- Department of Psychology, Center for Developmental Psychobiology, Binghamton University SUNY, Binghamton, NY 13902-6000, USA
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Molina JC, Spear NE, Spear LP. The International society for developmental psychobiology 39th annual meeting symposium: Alcohol and development: beyond fetal alcohol syndrome. Dev Psychobiol 2007; 49:227-42. [PMID: 17380525 PMCID: PMC1976664 DOI: 10.1002/dev.20224] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
As has been repeatedly demonstrated, alcohol can exert deleterious morphological and physiological effects during early stages in development. The present review examines nonteratological links existing between alcohol and ontogeny. Human and animal studies are taken into consideration for the analysis of fetal, neonatal, infantile, adolescent, and adult responsiveness to the drug. Sensitivity to alcohol's chemosensory and postabsorptive properties, as well as learning and memory processes mediated by such properties, are examined from this developmental perspective. The studies under discussion indicate that, within each stage in development, we can trace alcohol-related experiences capable of determining or modulating alcohol seeking and intake patterns.
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Affiliation(s)
- Juan Carlos Molina
- Department of Psychology, Binghamton University, PO Box 6000, Binghamton, NY 13902-6000, E-mail:
| | - Norman E. Spear
- Department of Psychology, Binghamton University, PO Box 6000, Binghamton, NY 13902-6000, E-mail:
| | - Linda P. Spear
- Department of Psychology, Binghamton University, PO Box 6000, Binghamton, NY 13902-6000, E-mail:
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Truxell EM, Molina JC, Spear NE. Ethanol intake in the juvenile, adolescent, and adult rat: effects of age and prior exposure to ethanol. Alcohol Clin Exp Res 2007; 31:755-65. [PMID: 17386073 DOI: 10.1111/j.1530-0277.2007.00358.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Initial ingestion of ethanol by naïve rats has seemed to decrease dramatically with age. During the preweanling period, infant rats consume large quantities of high concentrations of ethanol without initiating procedures, in some instances exceeding doses required for severe motor incoordination. During adulthood, however, initial ingestion of ethanol without initiation procedures is low and infrequent. In the present study, the ontogeny of ethanol intake was measured in juvenile, adolescent and adult rats using a technique [consume off the floor (COF)] similar to that used to study intake during infancy. How this initial experience with ethanol affected subsequent affinity for ethanol intake was later assessed using 2-bottle choice preference tests. METHODS Independent ingestion of ethanol was measured at 3 developmental periods, the juvenile period (P22-P28), adolescence (P30-P34) and adulthood (P60-P64), with systematic variation in ethanol concentration (15 or 30% v/v) and palatability (sweetness) of ethanol. Blood ethanol concentrations (BECs) were determined in all animals. This dependent variable served as an estimate of absolute ethanol ingestion. Three COF sessions were conducted for each age group. Following these sessions animals' ethanol consumption was also assessed using a 2-bottle choice test (water vs 15% v/v unsweetened ethanol). RESULTS In all experiments, groups consuming 30% v/v ethanol exhibited significantly higher BECs than those exposed to 15% v/v ethanol. Adding saccharin to the ethanol increased absolute ethanol ingestion in only the oldest animals. During the pre-exposure phase (COF sessions) of each experiment, absolute ethanol intake was found to decline with repeated exposures. Sex effects were particularly evident during later stages of ontogeny (adolescents and adults). The overall pattern of results indicated that juveniles relative to adults show a marked predisposition to consume highly concentrated ethanol solutions and that BECs derived from the COF sessions influenced ethanol acceptance patterns in the subsequent 2-bottle test. CONCLUSIONS Using the (COF) technique with BECs as an estimate of intake, absolute ethanol consumption seems to be quite high early in ontogeny and decline gradually into adulthood. Adding saccharin to ethanol solutions at the concentration used in the present study (0.1%) was generally not sufficient to increase absolute ethanol intake from the floor, except during adulthood. The experimental strategy employed in this study represents a novel approach for examining ethanol acceptance patterns across ontogeny and how experience with the process of intoxication affects subsequent ethanol preferences.
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Affiliation(s)
- Eric M Truxell
- Department of Psychology, Binghamton University, Binghamton, New York 13902-6000, USA
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Molina JC, Pautassi RM, Truxell E, Spear N. Differential motivational properties of ethanol during early ontogeny as a function of dose and postadministration time. Alcohol 2007; 41:41-55. [PMID: 17452298 PMCID: PMC1906736 DOI: 10.1016/j.alcohol.2007.01.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Revised: 01/29/2007] [Accepted: 01/29/2007] [Indexed: 10/23/2022]
Abstract
While appetitive reinforcement effects of ethanol are easily detected in rat neonates, such phenomena rarely have been observed in older infants. Recently, Molina et al. [Molina, J. C., Ponce L. F., Truxell, E., & Spear N. E. (2006). Infantile sensitivity to ethanol's motivational effects: ethanol reinforcement during the third postnatal week. Alcohol Clin Exp Res 30, 1506-1519] reported such effects of ethanol in 14-day-olds using a second-order conditioning procedure. Infants also appear to be sensitive to biphasic reinforcement or general motivational effects of ethanol, with appetitive effects seeming to occur early in the state of intoxication and aversive effects predominant during late stages, but tests have been inconclusive. The present study examined the possibility of biphasic motivational effects of ethanol during infancy through the use of second-order conditioning procedures. Preweanling rats (14 days old) experienced intraoral water infusions (conditioned stimulus, CS) either 5-20 or 30-45 min after administration of 0.5 or 2.0 g/kg i.g. ethanol. Pups were then exposed to the CS while over a novel texture (second-order phase). Tests of tactile preference for that texture followed. Locomotive, thermal, hormonal (corticosterone release), and pharmacokinetic patterns likely to underlie the acquisition of ethanol-mediated conditioning were also examined in subsequent experiments. Intraoral CSs paired with either early or late effects of low-dose ethanol (0.5 g/kg, blood ethanol concentration: 40 mg%) became positive second-order reinforcers. Appetitive effects were also exhibited by pups exposed to the CS during commencement of the toxic episode induced by a 2.0 g/kg ethanol dose, 5-20 min after administration of ethanol, whereas aversions emerged when CS presentation occurred 30-45 min postadministration time (blood ethanol concentrations: 157 and 200 mg%, respectively). Overall, the results indicate that infants rapidly detect differential motivational properties of ethanol as a function of dose or drug postadministration time. Relatively neutral stimuli associated with these properties are later capable of acting as either positive or aversive reinforcers. Thermal and motor responses that accompany ethanol intoxication do not seem to be directly associated with differential hedonic properties of the drug at this stage of development.
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Affiliation(s)
- Juan Carlos Molina
- Center for Developmental Psychobiology, Binghamton University, Binghamton, NY 13902-6000, USA
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Molina JC, Ponce LF, Truxell E, Spear NE. Infantile sensitivity to ethanol's motivational effects: Ethanol reinforcement during the third postnatal week. Alcohol Clin Exp Res 2006; 30:1506-19. [PMID: 16930213 DOI: 10.1111/j.1530-0277.2006.00182.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Although tests specific to newborn rats have frequently verified their susceptibility to the reinforcing properties of ethanol, demonstration of comparable reinforcing effects in older infants has been elusive. Using a second-order conditioning procedure, the present study assessed in preweanling rats whether pairing with early postabsorptive effects of ethanol would render intraorally delivered gustatory stimuli capable of positive reinforcement for association with a salient texture. Direct reinforcing effects of ethanol were also evaluated through intake tests of gustatory stimuli previously paired with the drug. Blood ethanol levels (BELs) were determined for each of the ethanol doses used. METHODS Pups (14 days old) were stimulated with intraoral infusion of sucrose (10% v/v), water, or quinine (0.0045% w/v) 5 minutes after being intragastrically (i.g.) administered 0.00, 0.25, 0.50, or 2.00 g/kg ethanol (Experiments 1 and 2). These stimuli were then briefly presented while pups experienced a rough texture (sandpaper). Rats were subsequently evaluated in a 2-way texture location test (sandpaper vs smooth surface). In Experiment 3, sucrose, water, or quinine was paired with early postabsorptive effects of ethanol (0.00, 0.50, or 2.0 g/kg). Consumption of these stimuli was later assessed. Motor activity patterns during the intake test were also evaluated. In Experiment 4, BELs corresponding to 0.25, 0.50, or 2.0 g/kg ethanol were determined 5 and 20 minutes after i.g. administration (time periods were in accord with the onset and offset of intraoral stimulation used in the previous experiments). RESULTS Intraoral infusion of sucrose, water, or quinine, while under a state of sobriety and paired with sandpaper, resulted in roughly 50% preference for this texture. Sandpaper preferences were significantly elevated in pups that had experienced sucrose or water in a nonsober state-while under the effects of ethanol (Experiments 1 and 2). This indicated reinforcing effects of the ethanol intoxication. Pairing ethanol intoxication directly with consumption of sucrose, water, or quinine did not affect their later consumption. Yet, there were clear indications that this pairing resulted in conditioned behavioral activity patterns. Blood ethanol levels corresponding to the ethanol doses used here ranged between 10 and 150 mg%. CONCLUSIONS Infants appear sensitive to pharmacological reinforcing properties of low and relatively high ethanol doses. This sensitivity was revealed indirectly, by pairing gustatory stimuli with ethanol intoxication and then allowing these stimuli to act as second-order reinforcement for a quite different (tactile) stimulus. Behavioral activation elicited by the gustatory stimuli previously paired with a state of intoxication seems to compete with the expression of ethanol's motivational properties as assessed through intake tests.
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Affiliation(s)
- Juan Carlos Molina
- Center for Developmental Psychobiology, Department of Psychology, Binghamton University-State University of New York, Binghamton, New York 13902-6000, USA
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13
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Nizhnikov ME, Varlinskaya EI, Petrov ES, Spear NE. Reinforcing properties of ethanol in neonatal rats: involvement of the opioid system. Behav Neurosci 2006; 120:267-80. [PMID: 16719691 DOI: 10.1037/0735-7044.120.2.267] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Toward understanding why infant rats ingest high levels of ethanol without initiation procedures, the authors tested effects of mu and kappa receptor antagonists on ethanol reinforcement in neonatal rats. After an intracisternal injection of CTOP (micro antagonist), nor-Binaltorphimine (kappa antagonist), or saline, newborn (3-hr-old) rats were given conditioning pairings of an odor with intraorally infused ethanol or a surrogate nipple with ethanol administered intraperitoneally (to minimize ethanol's gustatory attributes). In each case, these opioid antagonists reduced or eliminated ethanol's reinforcement effect. The same effects occurred with saccharin as the reinforcer in olfactory conditioning. The results imply that activation of mu and kappa receptors, apparently acting jointly, is necessary for reinforcement or that antagonists of this activity impair basic conditioning.
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Affiliation(s)
- Michael E Nizhnikov
- Center for Developmental Psychobiology, Department of Psychology, Binghamton University, State University of New York, Binghamton, NY 139002-6000, USA.
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Truxell E, Spear NE. Immediate acceptance of ethanol in infant rats: ontogenetic differences with moderate but not high ethanol concentration. Alcohol Clin Exp Res 2005; 28:1200-11. [PMID: 15318119 DOI: 10.1097/01.alc.0000134220.34842.18] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND During the preweanling period, infant rats consume large quantities of ethanol without initiating procedures. Ethanol intake during this period has seemed to be age related, with peak consumption occurring near the end of the second postnatal week, on postnatal day (P)12, but only a narrow range of conditions has been tested. METHODS Independent ingestion of ethanol was measured at each of two ages, P12 and P18, with systematic variation in ethanol concentration, duration of exposure, and mode of fluid presentation. Ethanol ingestion was measured in terms of percentage body weight gain, grams of absolute ethanol ingested per unit body weight, and blood ethanol concentration. RESULTS Ingestion of 30% ethanol during a 40-min period led to blood ethanol concentrations approaching 300 mg/100 ml at both P12 and P18. For ethanol concentrations of 10 or 20%, ingestion at P12 was greater than at P18. When ethanol was available from ethanol-soaked Kimwipe on the floor, ethanol intake transdermally or by inhalation was apparent but accounted for less than half of the overall ethanol intake. It was clear that for older infants, which are susceptible to ethanol's diuretic effects and are much more likely to self-void than those at P12, measurement of intake by percentage body weight gain can underestimate ethanol ingestion. CONCLUSIONS The infant rat ingests extraordinarily high levels of ethanol, in concentrations as high as 30%, without initiation procedures. Acceptance of ethanol by infants on first exposure contrasts with the conventional rejection of these concentrations by adults. It is unclear why younger infants (P12) consume more 10 and 20% ethanol than older (P18) infants. These and other differences in ethanol intake between infants and older animals may be due initially to the relative ontogeny of receptors for bitter and sweet taste and subsequently to other factors.
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Affiliation(s)
- Eric Truxell
- Department of Psychology, Binghamton University, Binghamton, New York 13902-6000, USA
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Petrov ES, Varlinskaya EI, Spear NE. Reinforcement from pharmacological effects of ethanol in newborn rats. Alcohol Clin Exp Res 2004; 27:1583-91. [PMID: 14574228 DOI: 10.1097/01.alc.0000089960.62640.58] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND The preweanling period in the rat is characterized by acceptance of substantial amounts of ethanol and susceptibility to its reinforcing effects. It has been unclear, however, whether the neurobiological basis of ethanol reinforcement properties at this age is in ethanol's olfactory, gustatory, or pharmacological effects. METHODS The effectiveness of intraperitoneal (ip) ethanol as a reinforcer for newborn (3-hr-old) rats was tested toward separation of the orosensory and pharmacological sources of ethanol reinforcement. Responsiveness to a test nipple by pups given such pairings was compared with that of pups given unpaired presentations of the nipple and ethanol. RESULTS Reinforcement was assessed in terms of response to a surrogate nipple 1 hr after a single pairing of a similar nipple providing water (conditioned stimulus) and ip injection of ethanol (0.125, 0.25, 0.50, or 0.75 g/kg; unconditioned stimulus). Significant effects of ethanol reinforcement occurred with the lower doses (0.125 and 0.25 g/kg); higher doses of ethanol (0.50 and 0.75 g/kg) had no significant reinforcement effect. A second experiment determined that for conditioning with ip ethanol as the unconditioned stimulus, a conditioned stimulus consisting of only ingesting water or only suckling on an empty nipple also yielded significant reinforcing effects of ethanol, although with less strength than their combination. Both reinforcing doses of ethanol, 0.125 and 0.25 g/kg, yielded detectable concentrations of ethanol in the blood 5 min after injection, which were sustained at a significantly lower level 60 min after administration. CONCLUSIONS These data indicate that aside from possible, and likely weak, hematogenic sources of gustatory and olfactory attributes of ethanol, the basis of ethanol's reinforcement effect in neonatal rats is primarily pharmacological. For the pharmacological effects of ethanol to be reinforcing for the neonatal rat, concurrent appetitive activity on a nipple providing a fluid may be necessary for a substantial effect with this paradigm.
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Affiliation(s)
- Evgeniy S Petrov
- Center for Developmental Psychobiology, Department of Psychology, Binghamton University-State University of New York, Binghamton, New York 13902-6000, USA
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Cheslock SJ, Varlinskaya EI, Petrov ES, Silveri MM, Spear LP, Spear NE. Ethanol as a Reinforcer in the Newborn's First Suckling Experience. Alcohol Clin Exp Res 2001. [DOI: 10.1111/j.1530-0277.2001.tb02226.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Petrov ES, Varlinskaya EI, Spear NE. Self-administration of ethanol and saccharin in newborn rats: Effects on suckling plasticity. Behav Neurosci 2001. [DOI: 10.1037/0735-7044.115.6.1318] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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McKinzie D, Cox R, Murphy J, Li TK, Lumeng L, McBride W. Voluntary Ethanol Drinking During the First Three Postnatal Weeks in Lines of Rats Selectively Bred for Divergent Ethanol Preference. Alcohol Clin Exp Res 1999. [DOI: 10.1111/j.1530-0277.1999.tb04088.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Wang Z, Barker TH, Fuller GM. Alcohol at Moderate Levels Decreases Fibrinogen Expression In Vivo and In Vitro. Alcohol Clin Exp Res 1999. [DOI: 10.1111/j.1530-0277.1999.tb04093.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Varlinskaya EI, Petrov ES, Cheslock SJ, Spear NE. A New Model of Ethanol Self-Administration in Newborn Rats: Gender Effects on Ethanol Ingestion Through a Surrogate Nipple. Alcohol Clin Exp Res 1999. [DOI: 10.1111/j.1530-0277.1999.tb04359.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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