Selective M₁ muscarinic acetylcholine receptor (mAChR) agonists are being developed for possible therapeutic application in a number of disease states. However, activation of mAChRs using broad-spectrum agonists has also been shown to produce hyper-excitability within the brain which, at the behavioural level, is manifest as seizure activity. The aim of the current study was to assess whether selective M₁ receptor agonists promote pathological patterns of activity within the hippocampus in vitro. Extracellular recordings were used to monitor spontaneous field potentials in 450μm coronal rat hippocampal slices [1]. Application of the M1 selective agonist 77LH281 (10μM) resulted in a gamma frequency oscillatory activity (n=10, mean dominant frequency = 32 ± 3.6 Hz) that was sensitive to AMPA receptor blockade (2μM NBQX). In contrast, application of the broad spectrum mAChR agonist oxotremorine-M (10μM) induced inter-ictal-like epileptiform bursts which, in many instances (n=11 of 22), transformed into more prolonged ictal-like discharges. We also assessed whether mAChRs modulated established epileptiform activities. Specifically, convulsant regimes including potassium channel blockade (4AP, 20μM), blockade of GABA_A receptor-mediated inhibition (bicuculline, 20μM) or enhanced NMDA receptor activation (0mM Mg²⁺ perfusion medium) were used to induce epileptiform activity[1]. Subsequent co-application of 10μM 77LH281 did not produce any significant changes in epileptiform burst frequency in any of the three models examined (120 ± 30 %, 144 ± 74 % and 114 ± 35 %; all p>0.05; n=10-17). Conversely, co-application of 10μM oxotremorine-M significantly increased epileptiform burst frequency in all models investigated (180 ± 34 %, 401 ± 108 % and 148 ± 21 %; all p<0.05; n = 8-10). Moreover, in the majority of slices tested, 10μM oxotremorine-M converted the network from inter-ictal-like bursting behaviour to prolonged ictal-like patterns of activity (n=15 of 24, 9 of 13 and 11 of 16 slices for 4AP, bicuculline and 0mM Mg²⁺ models respectively). These results suggest that, in contrast to the broad spectrum mAChR agonist oxotremorine-M, the selective M₁ receptor agonist 77LH281 does not display a propensity to induce, or enhance, epileptiform activity.