Hippocampal theta oscillations are key elements in various behavioral and cognitive processes. Based on the dualistic theory of theta activity, one can differentiate between atropine-sensitive and atropine-insensitive theta activity. Urethane- induced atropine-sensitive theta oscillations are driven by muscarinic signal transduction pathways with PLCb1 deletion resulting in complete abolishment of theta oscillations. Recent findings illustrate that Ca_v2.3 Ca²⁺ channels are important targets of muscarinic signalling in the hippocampus mediating plateau potential generation and epileptiform bursting. In addition, they might be involved in complex rhythm generation and maintenance in the septohippocampal network. To investigate the physiological implications of Ca_v2.3 Ca²⁺ channels in hippocampal theta oscillations we performed radiotelemetric deep, intrahippocampal (CA1) recordings in urethane (800 mg/kg ip.) and atropine (50 mg/kg ip.) treated control and Ca_v2.3^-/- mice followed by frequency analysis of EEG data. Our results demonstrate, that Ca_v2.3 ablation other than PLCb1 deletion does not result in complete abolishment of urethane-induced theta- oscillation and is only partially inhibited by subsequent atropine treatment. In addition, sensory stimuli were also capable of inducing theta activity in Ca_v2.3^-/- mice. Frequency analysis of EEG recordings further suggests that theta oscillation architecture is altered in Ca_v2.3 deficient mice. Our data suggest for the first time, that Ca_v2.3 voltage-gated gated Ca²⁺-channels are an important factor in septohippocampal synchronization associated with theta oscillation.