Update on the connectivity of the paraventricular nucleus of the thalamus and its position within limbic corticostriatal circuits.

The paraventricular nucleus of the thalamus (PVT) is generating interest because evidence establishes a role for this midline thalamic nucleus in behavior. Early tracing studies demonstrated that afferent fibers from the PVT and limbic cortex converge with dopamine fibers within subcompartments of the ventral striatum. Subsequent tracing studies expanded on these observations by establishing that the PVT provides a dense projection to a continuum of striatal-like regions that include the nucleus accumbens and the extended amygdala.

Functional properties of corticothalamic circuits targeting paraventricular thalamic neurons.

Corticothalamic projections to sensorimotor thalamic nuclei show modest firing rates and serve to modulate the activity of thalamic relay neurons. By contrast, here we find that high-order corticothalamic projections from the prelimbic (PL) cortex to the anterior paraventricular thalamic nucleus (aPVT) maintain high-frequency activity and evoke strong synaptic excitation of aPVT neurons in rats. In a significant fraction of aPVT cells, such high-frequency excitation of PL-aPVT projections leads to a rapid decay of action potential amplitudes, followed by a depolarization block (DB) that strongly limits aPVT maximum firing rates, thereby regulating both defensive and appetitive behaviors in a frequency-dependent manner.

Analysis of Monosynaptic Inputs to Thalamic Paraventricular Nucleus Neurons Innervating the Shell of the Nucleus Accumbens and Central Extended Amygdala.

The paraventricular nucleus of the thalamus (PVT) sends dense projections to the shell of the nucleus accumbens (NAcSh), dorsolateral region of the bed nucleus of the stria terminalis (BSTDL) and the lateral region of central nucleus of the amygdala (CeL). Projection specific modulation of these pathways has been shown to regulate appetitive and aversive behavioral responses. The present investigation applied an intersectional monosynaptic rabies tracing approach to quantify the brain-wide sources of afferent input to PVT neurons that primarily project to the NAcSh, BSTDL and CeL.

Convergence of monosynaptic inputs from neurons in the brainstem and forebrain on parabrachial neurons that project to the paraventricular nucleus of the thalamus.

The paraventricular nucleus of the thalamus (PVT) projects to areas of the forebrain involved in regulating behavior. Homeostatic challenges and salient cues activate the PVT and evidence shows that the PVT regulates appetitive and aversive responses. The brainstem is a source of afferents to the PVT and the present study was done to determine if the lateral parabrachial nucleus (LPB) is a relay for inputs to the PVT.