Physiological Mapping of Local Inhibitory Inputs to the Hypothalamic Paraventricular Nucleus

Abstract

Local inhibitory synaptic inputs to neurons of the rat hypothalamic paraventricular nucleus (PVN) were studied by using glutamate microstimulation and conventional intracellular and whole-cell patch-clamp recording in coronal, horizontal, and parasagittal slices of rat hypothalamus. PVN cells were classified as magnocellular or parvocellular neurons on the basis of electrophysiological and post hoc immunohistochemical analyses; GABA-producing neurons were localized with in situ hybridization. Glutamate microstimulation of different sites around the PVN evoked volleys of postsynaptic potentials in 43% of the PVN neurons tested. Some responses to stimulation at each site were blocked by bicuculline, suggesting that they were mediated by the activation of presynaptic GABA neurons. In the coronal plane, presynaptic inhibitory sites were located lateral to the PVN and ventral to the fornix, corresponding to the lateral hypothalamic area and the posterior bed nucleus of the stria terminalis (BNST). In the horizontal plane, presynaptic inhibitory sites were found rostral, lateral, and caudal to the nucleus, corresponding to parts of the anterior hypothalamic area, the posterior BNST, the medial preoptic area, and the dorsomedial hypothalamus. In the parasagittal plane, presynaptic inhibitory neurons were revealed at sites rostral and caudal to the nucleus, corresponding to the medial preoptic area and the dorsomedial hypothalamus, and in a site dorsal to the optic chiasm that included the suprachiasmatic nucleus. These presynaptic sites each contained GABA-producing neurons based on in situ hybridization with a glutamic acid decarboxylase riboprobe and together formed a three-dimensional ring around the PVN. Unexpectedly, both magnocellular and parvocellular neurons received inhibitory synaptic inputs from common sites.

Suprachiasmatic GABAergic Inputs to the Paraventricular Nucleus Control Plasma Glucose Concentrations in the Rat via Sympathetic Innervation of the Liver

“…GABAergic SCN inputs to the autonomic PVN neurons have been demonstrated in a number of electrophysiological experiments (Hermes et al, 1996;Cui et al, 2001;Wang et al, 2003). In addition, there is also evidence for GABAergic projections from the DMH to the PVN (Boudaba et al, 1996). Because the DMH is also a target area for SCN projections (Watts et al, 1987;Buijs et al, 1993), the SCN might use both direct and indirect GABAergic projections to the preautonomic neurons in the PVN to control basal plasma glucose concentrations, implying that SCN projections to the GABAergic DMH neurons are stimulatory.…”

“…The hypothalamic areas for TTX infusion were selected on the basis of their known projections to the PVN (Luiten and Room, 1980;Boudaba et al, 1996) and the presence of third-order labeling after virus injection in the liver. Silencing of either the SCN or DMH input caused an increase in plasma glucose concentrations, although to a lesser extent than those observed when all of the GABAergic inputs to the PVN were silenced.…”

Regional Differentiation of the Medial Prefrontal Cortex in Regulating Adaptive Responses to Acute Emotional Stress

“…sponse systems (Roland and Sawchenko, 1993;Boudaba et al, 1996). Although direct evidence to define such circuitry (Fig.…”

Excitatory and inhibitory local circuit input to the rat dorsal motor nucleus of the vagus originating from the nucleus tractus solitarius

“…Chemical stimulation techniques typically do not depolarize fibers of passage, allowing neuron cell bodies and dendrites to be selectively activated, as they contain ionotropic glutamate receptors [3,6,10,19,26]. We previously demonstrated an inhibitory connection between the NTS and DMV using glutamate photostimulation at a single point [11].…”

“…The glutamate microdrop technique involves pressure applying Lglutamate via a modified patch pipette directly onto cells [3,9,10,26]. This technique selectively depolarizes soma and dendrites, but not axons.…”