1. l-AP-4 depressed local synaptic glutamate release in the lateral hypothalamus.
l-AP-4 depressed local synaptic glutamate release in the lateral hypothalamus. A, Schematic representation of the lateral hypothalamic region dissected out to study the local excitatory inputs to hypocretin cells. ARH, Arcuate nucleus of the hypothalamus; cpd, cerebral peduncle; DMH, dorsomedial hypothalamus; fx, fornix; LHA, lateral hypothalamic area; ME, median eminence; opt, optic tract; VMH, ventromedial hypothalamus; V3, third ventricle; ZI, zonaincerta. B, The group III mGluR agonist l-AP-4 (100 μm) reversibly depressed the frequency of spontaneous EPSCs. C, Trace 1 shows the excitatory synaptic response, but not direct response, to glutamate micro application 1 mm away from the recorded cell. Trace 2 shows that, in the presence of TTX, the glutamate microdrop failed to increase the EPSC frequency. Trace 3 shows the glutamate microdrop experiment after ionotropic glutamate receptors blockade. No increase in the EPSC frequency was detected. In trace 4 is shown the slow inward current evoked by glutamate directly applied to the recorded cell. D, TTX at 0.5 μm changed (left shift) the cumulative fractions of the EPSC amplitude. Arrowhead shows the point at which all events in TTX can be accounted for (maximum of 27 pA). E, l-AP-4 (100 μm) reduced the frequency of large spike-dependent EPSCs (amplitude, ≥28 pA) by 40.5 ± 9.3% (*p < 0.05; n = 5).
Claudio Acuna-Goycolea et al. J. Neurosci. 2004;24:
©2004 by Society for Neuroscience