60 ± 0.04 × 106), with the anterior half of both segments being more densely innervated than the posterior half. Dorsoventral and mediolateral decreasing gradients of SERT varicosities occur in both pallidal segments, but are statistically significant only in the GPi. The neuronal density being significantly greater in the GPe (3.41 ± 0.23 × 103 neurons/mm3) than in the GPi (2.90 ± 0.11 × 103), the number of 5-HT axon varicosities per pallidal neuron was found to be superior in the GPi (201 ± 27) than in the GPe (156 ± 26). At the electron microscopic level, GW-572016 SERT+ axon varicosities are comparable in size and vesicular

content in GPi and GPe, where they establish mainly asynaptic contacts with unlabeled profiles. Less than 25% of SERT+ varicosities display a synaptic specialization, which is of the symmetrical or asymmetrical type and occurs exclusively on pallidal dendrites. No SERT+ axo-axonic synapses are present, suggesting that 5-HT exerts its well-established modulatory selleck action upon various pallidal afferents mainly through diffuse transmission, whereas its direct control of pallidal neurons results from both volumic and synaptic release of the transmitter. “
“D-cycloserine (DCS) is currently under clinical trials for a number of neuropsychiatric conditions and has been found to augment fear extinction in rodents and exposure therapy

in humans. However, the molecular mechanism of DCS action

in these multiple modalities remains unclear. Here, we describe the effect of DCS administration, alone or in conjunction with extinction training, on neuronal activity (c-fos) and neuronal plasticity [phospho-extracellular signal-regulated kinase isothipendyl (pERK)] markers using immunohistochemistry. We found that intraperitoneal administration of DCS in untrained young rats (24–28 days old) increased c-fos- and pERK-stained neurons in both the prelimbic and infralimbic division of the medial prefrontal cortex (mPFC) and reduced pERK levels in the lateral nucleus of the central amygdala. Moreover, DCS administration significantly increased GluA1, GluN1, GluN2A, and GluN2B expression in the mPFC. In a separate set of animals, we found that DCS facilitated fear extinction and increased pERK levels in the infralimbic prefrontal cortex, prelimbic prefrontal cortex intercalated cells and lateral nucleus of the central amygdala, compared with saline control. In the synaptoneurosomal preparation, we found that extinction training increased iGluR protein expression in the mPFC, compared with context animals. No significant difference in protein expression was observed between extinction-saline and extinction-DCS groups in the mPFC. In contrast, in the amygdala DCS, the conjunction with extinction training led to an increase in iGluR subunit expression, compared with the extinction-saline group.