Robust Intrinsic Dorsoventral Organization of Hippocampal Sharp Wave–Ripples Persists During Cannabinoid Modulation

Background/Objectives: The hippocampus exhibits pronounced functional and physiological heterogeneity along its dorsoventral axis. Sharp wave–ripple (SWR) complexes are highly organized hippocampal network events that depend on coordinated excitation and inhibition and contribute to memory processing. This study investigated whether modulation of the cannabinoid system differentially affects SWRs and associated neuronal activity in the dorsal and ventral hippocampus. Methods: Extracellular field potentials and multiunit activity (MUA) were recorded from the CA1 stratum pyramidale of acute dorsal and ventral rat hippocampal slices. Spontaneous SWRs were analyzed under control conditions and following application of the cannabinoid type 1 (CB1) receptor agonists ACEA and WIN55,212-2, cannabidiol (CBD), and the G-protein-gated inwardly rectifying potassium channel blocker tertiapin-Q. CB1 receptor expression was assessed in dorsal and ventral CA3 using Western blot analysis. Results: Baseline recordings revealed pronounced dorsoventral differences in SWR dynamics. Ventral slices exhibited shorter inter-event intervals, larger sharp-wave amplitudes, higher ripple frequency and power, and greater SWR-associated neuronal activity than dorsal slices. Under the present experimental and analytical conditions, ACEA, WIN55,212-2, and CBD did not produce statistically significant changes in any of the examined SWR or MUA parameters. Tertiapin-Q selectively increased ripple power but did not reveal cannabinoid sensitivity when followed by WIN55,212-2 application. CB1 receptor expression was comparable between dorsal and ventral CA3. Conclusions: Despite marked intrinsic dorsoventral differences in SWR dynamics, acute cannabinoid-system modulation produced no statistically detectable changes in most SWR and MUA parameters examined. These findings indicate that the intrinsic dorsoventral organization of hippocampal SWR activity is robust and remains preserved during acute cannabinoid-system modulation under the present experimental conditions.