As the downstream target of AC1, cyclic-AMP(cAMP)-dependent protein kinase (PKA) has been well documented, which may activate MEK and ERK/MAPK via the activation of AC1. on the maintenance of cingulate LTP. Inhibitors of c-Jun N-terminal kinase (JNK) and p38, other members of MAPK family, SP600125 and SB203850, suppressed the induction of cingulate LTP generated by the pairing protocol. Thus, our study suggests that the MAPK signaling pathway is involved in the induction of cingulate LTP and plays a critical role in physiological conditions. Introduction The prefrontal cortex, including the anterior cingulate cortex (ACC) is believed to play important roles MS-444 in emotion, learning, memory and persistent pain in the adult brain [1-7]. Long-term potentiation (LTP), MS-444 known to be involved in learning and memory, is a key synaptic mechanism for cortical synaptic plasticity [8]. Recent studies demonstrate that LTP can be induced in the cingulate slices [3,9,10]. However, several recent studies showed that molecular signaling pathways involved in the synaptic potentiation in the ACC differ from those in the hippocampus. For example, both N-methyl-D-aspartate (NMDA) receptor subunit 2A and 2B (NR2A and NR2B) contribute to cingulate LTP [3], while NR2A is preferentially contributing to hippocampal LTP [11,12]. For calcium-related signaling messengers, calcium-calmodulin (CaM) dependent adenylyl cyclase (AC) type 1 is critical for synaptic LTP in the ACC [9], while AC1 deletion alone did MS-444 not affect hippocampal LTP [13]. On the other hand, the downstream targets of calcium-stimulated cAMP-dependent signaling pathways underlying LTP in the ACC synapses have been far less investigated compared to hippocampal synapses. As the downstream target of cAMP signaling pathways, mitogen-activated protein kinase (MAPK) is well characterized in the hippocampus [14,15]. MS-444 The MAPK is a family of serine/threonine protein kinases that transduce extracellular signals from cell surface receptors to the cell nucleus [16,17]. The MAPK cascade includes extracellular signal-regulated (ERK), p38, c-Jun N-terminal kinase (JNK), and ERK5 [17]. The activation of ERK is coupled to stimulation of cell surface receptors via several different upstream signaling pathways, and plays critical roles in the regulation of gene expression and cell proliferation [18]. In neurons, the ERK signaling pathway is activated by synaptic activity such as membrane depolarization, calcium influx and neurotrophins [19-21]. Furthermore, the ERK signaling pathway might regulate synaptic targets to control important functions such as synaptic plasticity, learning and memory in the adult brain [15,22,23]. However, the role of ERK signaling pathway in the cingulate synaptic plasticity has not been investigated. In the present study, we performed whole-cell patch-clamp recordings from cingulate neurons of adult mice and investigated the role of MAPK in the cingulate synaptic potentiation. Here, we show that LTP induced by three different induction protocols were completely blocked by the MAPK/ERK kinase (MEK) inhibitor applied postsynaptically. Furthermore, we found that the MEK inhibitors did not affect the maintenance of cingulate LTP. Inhibitors of c-Jun N-terminal kinase (JNK) and p38 also suppressed the induction of cingulate LTP generated by the pairing protocol. These results suggest that the activation of MAPK including ERK, JNK and p38, is critical for the induction of LTP in the ACC. Results Postsynaptic injection of MAPK inhibitors blocks the cingulate LTP We performed conventional whole-cell patch-clamp recordings from visually identified pyramidal neurons in the layer II/III of cingulate slices. Fast EPSCs were obtained by delivering focal electrical stimulation to the layer V. First, we identified pyramidal neurons based on the pyramidal shape of IGFBP3 their somata by loading Lucifer yellow into the MS-444 intracellular solution [3]. We also confirmed that the recordings were performed from cortical pyramidal cells by injecting depolarizing currents into the neuron. Injection of depolarizing currents into neurons induced repetitive action.