Exploring the Function of Hippocampal Oscillations
Tomomi Sakairi, Masanori Kawabata, Alain Rios, Yutaka Sakai, and Yoshikazu Isomura
(see article e0080252025)
Hippocampal oscillations called sharp-wave ripples (SWRs) occur during eating, drinking, and periods of behavioral immobility. However, studies have not examined whether SWRs are involved during slowed movement prior to consummatory behaviors (i.e., stopping to lick food or water). Herein, Sakairi et al. assessed SWRs in immobilized rats that were trained to hold pedals and release them to receive water, which they were granted every other time. As rats held the pedals, SWRs gradually increased. This effect was enhanced when the rats expected to receive water. Conversely, during pedal release and licking for water, SWRs decreased. A specific group of neurons in the hippocampus responded to pedal release and receiving water, supporting previous work. Other groups of neurons displayed changes in activity mirroring the SWR changes; neuron spikes diminished during pedal release and water licking and increased during pedal hold and the expectation of water. This work links hippocampal SWRs to making associations between actions and outcomes rather than reward intake.
Rat coronal section with arrowheads (inset) pointing to silicon probe tracks in the hippocampal CA1 area. The red staining is from Dil on the probe. Stratum oriens (s.o.), stratum pyramidale (s.p.), and stratum radiatum (s.r.) are labeled. See Sakairi et al. for more information.
Mechanism for Kappa Opioid-Mediated Adverse Symptoms
Durairaj Ragu Varman, Sammanda Ramamoorthy, and Lankupalle D. Jayanthi
(see article e0171252025)
Cocaine addiction affects neurotransmission in the mesolimbic system, which regulates reward-related behaviors. Studies suggest that cocaine hijacks the mesolimbic system by targeting dopamine transporters and influencing the way that dopamine interacts with the dynorphin/kappa opioid receptor (KOR) system. Researchers developing treatments for cocaine addiction have found that pharmaceuticals targeting KOR alleviate symptoms associated with the condition but also result in adverse side effects. Using biochemical and behavioral experiments, Ragu Varman et al. explored KOR-mediated mechanisms for symptoms like aversion, locomotor suppression, and cocaine reward enhancement in mice. The authors discovered a phosphorylation site in dopamine transporters (Thr53) that is required for KOR-mediated adverse symptoms. These findings point to an intersection in dopamine and opioid signaling that contributes to aversion, suppression of movement, and enhanced cocaine reward. According to the authors, this study may inform preclinical and clinical work on how to alleviate the adverse effects of KOR-based treatments.
Footnotes
This Week in The Journal was written by Paige McKeon
