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Repeated exposure to Delta(9)-tetrahydrocannabinol alters heroin-induced locomotor sensitisation and Fos-immunoreactivity.
Neuropharmacology 2005; 49(8):1189-200N

Abstract

The present study examined the effect of chronic exposure to Delta(9)-tetrahydrocannabinol (THC) on heroin-induced locomotor sensitisation and Fos-immunoreactivity (Fos-IR). Adult male albino Wistar rats (n=60) were injected intraperitoneally (i.p.) 21 times with vehicle, 0.05, 0.5, or 5.0mg/kg THC (once every 48 h for 41 days). Locomotor activity was assessed for 180 min on pre-exposure days 1, 21, and 41. Following a 2-week washout period, rats were divided into five equal groups (n=12) and injected subcutaneously (s.c.) with vehicle or heroin (0.5mg/kg). Locomotor activity was recorded for 240 min. In drug-naïve rats, heroin significantly increased locomotor activity. THC pre-exposure further increased heroin-induced locomotion. After an interval of 2 weeks, rats pre-exposed to vehicle and 5.0mg/kg THC in the first part of the experiment were randomly assigned to one of four treatment groups (n=6) and injected s.c. with vehicle or 0.5mg/kg heroin and perfused 2h later. Fos-IR was examined in several brain regions. Acute heroin increased Fos-IR in drug-naïve rats in the caudate-putamen (CPu; central, medial and dorsomedial regions), nucleus accumbens (NAC; core and shell regions), bed nucleus of the stria terminalis (BNST), lateral septum, central nucleus of the amygdala (CEA), periaqueductal grey (PAG; dorsolateral, dorsomedial, and lateral), and the Edinger-Westphal nucleus. Pre-exposure to THC significantly increased heroin-induced Fos-IR in the dorsomedial CPu and the NAC (core). Conversely, THC pre-exposure reduced heroin-induced Fos-IR in the BNST, CEA, and the PAG (dorsolateral and lateral). The present study demonstrates that THC pre-exposure increases the locomotor stimulating effects of heroin and provides new evidence for the neural correlates that may underlie cannabinoid and opioid cross-sensitisation.

Authors+Show Affiliations

School of Psychology, University of New England, Armidale, NSW 2351, Australia.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

16137723

Citation

Singh, M E., et al. "Repeated Exposure to Delta(9)-tetrahydrocannabinol Alters Heroin-induced Locomotor Sensitisation and Fos-immunoreactivity." Neuropharmacology, vol. 49, no. 8, 2005, pp. 1189-200.
Singh ME, McGregor IS, Mallet PE. Repeated exposure to Delta(9)-tetrahydrocannabinol alters heroin-induced locomotor sensitisation and Fos-immunoreactivity. Neuropharmacology. 2005;49(8):1189-200.
Singh, M. E., McGregor, I. S., & Mallet, P. E. (2005). Repeated exposure to Delta(9)-tetrahydrocannabinol alters heroin-induced locomotor sensitisation and Fos-immunoreactivity. Neuropharmacology, 49(8), pp. 1189-200.
Singh ME, McGregor IS, Mallet PE. Repeated Exposure to Delta(9)-tetrahydrocannabinol Alters Heroin-induced Locomotor Sensitisation and Fos-immunoreactivity. Neuropharmacology. 2005;49(8):1189-200. PubMed PMID: 16137723.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Repeated exposure to Delta(9)-tetrahydrocannabinol alters heroin-induced locomotor sensitisation and Fos-immunoreactivity. AU - Singh,M E, AU - McGregor,I S, AU - Mallet,P E, Y1 - 2005/08/30/ PY - 2004/12/16/received PY - 2005/07/13/revised PY - 2005/07/14/accepted PY - 2005/9/3/pubmed PY - 2006/1/18/medline PY - 2005/9/3/entrez SP - 1189 EP - 200 JF - Neuropharmacology JO - Neuropharmacology VL - 49 IS - 8 N2 - The present study examined the effect of chronic exposure to Delta(9)-tetrahydrocannabinol (THC) on heroin-induced locomotor sensitisation and Fos-immunoreactivity (Fos-IR). Adult male albino Wistar rats (n=60) were injected intraperitoneally (i.p.) 21 times with vehicle, 0.05, 0.5, or 5.0mg/kg THC (once every 48 h for 41 days). Locomotor activity was assessed for 180 min on pre-exposure days 1, 21, and 41. Following a 2-week washout period, rats were divided into five equal groups (n=12) and injected subcutaneously (s.c.) with vehicle or heroin (0.5mg/kg). Locomotor activity was recorded for 240 min. In drug-naïve rats, heroin significantly increased locomotor activity. THC pre-exposure further increased heroin-induced locomotion. After an interval of 2 weeks, rats pre-exposed to vehicle and 5.0mg/kg THC in the first part of the experiment were randomly assigned to one of four treatment groups (n=6) and injected s.c. with vehicle or 0.5mg/kg heroin and perfused 2h later. Fos-IR was examined in several brain regions. Acute heroin increased Fos-IR in drug-naïve rats in the caudate-putamen (CPu; central, medial and dorsomedial regions), nucleus accumbens (NAC; core and shell regions), bed nucleus of the stria terminalis (BNST), lateral septum, central nucleus of the amygdala (CEA), periaqueductal grey (PAG; dorsolateral, dorsomedial, and lateral), and the Edinger-Westphal nucleus. Pre-exposure to THC significantly increased heroin-induced Fos-IR in the dorsomedial CPu and the NAC (core). Conversely, THC pre-exposure reduced heroin-induced Fos-IR in the BNST, CEA, and the PAG (dorsolateral and lateral). The present study demonstrates that THC pre-exposure increases the locomotor stimulating effects of heroin and provides new evidence for the neural correlates that may underlie cannabinoid and opioid cross-sensitisation. SN - 0028-3908 UR - https://www.unboundmedicine.com/medline/citation/16137723/Repeated_exposure_to_Delta_9__tetrahydrocannabinol_alters_heroin_induced_locomotor_sensitisation_and_Fos_immunoreactivity_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0028-3908(05)00262-5 DB - PRIME DP - Unbound Medicine ER -