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Ashirova E, Contoreggi NH, Johnson MA, Al-Khayat FJ, Calcano GA, Rubin BR, O'Cinneide EM, Zhang Y, Zhou Y, Gregoire L, McEwen BS, Kreek MJ, Milner TA. Oxycodone injections not paired with conditioned place preference have little effect on the hippocampal opioid system in female and male rats. Synapse 2020; 75:e22182. [PMID: 32654187 DOI: 10.1002/syn.22182] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 06/28/2020] [Accepted: 07/03/2020] [Indexed: 12/12/2022]
Abstract
Oxycodone (Oxy) conditioned place preference (CPP) in Sprague Dawley rats results in sex-specific alterations in hippocampal opioid circuits in a manner that facilitates opioid-associative learning processes, particularly in females. Here, we examined if Oxy (3 mg/kg, I.P.) or saline (Sal) injections not paired with behavioral testing similarly affect the hippocampal opioid system. Sal-injected females compared to Sal-injected males had: (1) higher densities of cytoplasmic delta opioid receptors (DOR) in GABAergic hilar dendrites suggesting higher baseline reserve DOR pools and (2) elevated phosphorylated DOR levels, but lower phosphorylated mu opioid receptor (MOR) levels in CA3a suggesting that the baseline pools of activated opioid receptors vary in females and males. In contrast to CPP studies, Oxy-injections in the absence of behavioral tests resulted in few changes in the hippocampal opioid system in either females or males. Specifically, Oxy-injected males compared to Sal-injected males had fewer DORs near the plasma membrane of CA3 pyramidal cell dendrites and in CA3 dendritic spines contacted by mossy fibers, and lower pMOR levels in CA3a. Oxy-injected females compared to Sal-injected females had higher total DORs in GABAergic dendrites and lower total MORs in parvalbumin-containing dendrites. Thus, unlike Oxy CPP, Oxy-injections redistributed opioid receptors in hippocampal neurons in a manner that would either decrease (males) or not alter (females) excitability and plasticity processes. These results indicate that the majority of changes within hippocampal opioid circuits that would promote opioid-associative learning processes in both females and males do not occur with Oxy administration alone, and instead must be paired with CPP.
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Affiliation(s)
- Elina Ashirova
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
| | - Natalina H Contoreggi
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
| | - Megan A Johnson
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
| | - Fatima J Al-Khayat
- Weill Cornell Medicine in Qatar, Qatar Foundation, Education City, Doha, Qatar
| | - Gabriela A Calcano
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
| | - Batsheva R Rubin
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
| | - Emma M O'Cinneide
- Harold and Margaret Milliken Hatch Laboratory of Neuroendocrinology, The Rockefeller University, New York, NY, USA
| | - Yong Zhang
- The Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY, USA
| | - Yan Zhou
- The Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY, USA
| | - Lennox Gregoire
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
| | - Bruce S McEwen
- Harold and Margaret Milliken Hatch Laboratory of Neuroendocrinology, The Rockefeller University, New York, NY, USA
| | - Mary Jeanne Kreek
- The Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY, USA
| | - Teresa A Milner
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
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