Reduced Numbers of Corticotropin-Releasing Hormone Neurons in Narcolepsy Type 1.

Narcolepsy type 1 (NT1) is a chronic sleep disorder correlated with loss of hypocretin(orexin). In NT1 post-mortem brains, we observed 88% reduction in corticotropin-releasing hormone (CRH)-positive neurons in the paraventricular nucleus (PVN) and significantly less CRH-positive fibers in the median eminence, whereas CRH-neurons in the locus coeruleus and thalamus, and other PVN neuronal populations were spared: that is, vasopressin, oxytocin, tyrosine hydroxylase, and thyrotropin releasing hormone-expressing neurons. Other hypothalamic cell groups, that is, the suprachiasmatic, ventrolateral preoptic, infundibular, and supraoptic nuclei and nucleus basalis of Meynert, were unaffected. The surprising selective decrease in CRH-neurons provide novel targets for diagnostics and therapeutic interventions. ANN NEUROL 2022;91:282-288.

PET-CT and RNA sequencing reveal novel targets for acupuncture-induced lowering of blood pressure in spontaneously hypertensive rats.

Manual acupuncture (MA) can be used to manage high blood pressure; however, the underlying molecular mechanism remains unknown. To explore the mechanism of acupuncture in the treatment of hypertension, Wistar Kyoto rats (WKYs) and spontaneously hypertensive rats (SHRs) were subjected to either MA stimulation or the corresponding sham procedure as a negative control (Sham-MA) for 1 week. PET-CT scans, transcriptomics and molecular biology were used to evaluate the effect of MA. The results show that MA can regulate blood pressure in SHRs, change the glucose metabolism of the paraventricular hypothalamus (PVH), and affect the mRNA and protein expression levels of differentially expressed genes in the PVH. These genes may lower blood pressure by regulating angiotensin, endothelial function and inflammation. These findings reveal that MA regulates multiple biological processes and genes/proteins of the PVH, and provide a solid theoretical basis for exploring the mechanisms by which MA regulates hypertension.

Optogenetic identification of hypothalamic orexin neuron projections to paraventricular spinally projecting neurons.

Orexin neurons, and activation of orexin receptors, are generally thought to be sympathoexcitatory; however, the functional connectivity between orexin neurons and a likely sympathetic target, the hypothalamic spinally projecting neurons (SPNs) in the paraventricular nucleus of the hypothalamus (PVN) has not been established. To test the hypothesis that orexin neurons project directly to SPNs in the PVN, channelrhodopsin-2 (ChR2) was selectively expressed in orexin neurons to enable photoactivation of ChR2-expressing fibers while examining evoked postsynaptic currents in SPNs in rat hypothalamic slices. Selective photoactivation of orexin fibers elicited short-latency postsynaptic currents in all SPNs tested (n = 34). These light-triggered responses were heterogeneous, with a majority being excitatory glutamatergic responses (59%) and a minority of inhibitory GABAergic (35%) and mixed glutamatergic and GABAergic currents (6%). Both glutamatergic and GABAergic responses were present in the presence of tetrodotoxin and 4-aminopyridine, suggesting a monosynaptic connection between orexin neurons and SPNs. In addition to generating postsynaptic responses, photostimulation facilitated action potential firing in SPNs (current clamp configuration). Glutamatergic, but not GABAergic, postsynaptic currents were diminished by application of the orexin receptor antagonist almorexant, indicating orexin release facilitates glutamatergic neurotransmission in this pathway. This work identifies a neuronal circuit by which orexin neurons likely exert sympathoexcitatory control of cardiovascular function.NEW & NOTEWORTHY This is the first study to establish, using innovative optogenetic approaches in a transgenic rat model, that there are robust heterogeneous projections from orexin neurons to paraventricular spinally projecting neurons, including excitatory glutamatergic and inhibitory GABAergic neurotransmission. Endogenous orexin release modulates glutamatergic, but not GABAergic, neurotransmission in these pathways.

Subcortical aphasia: three different language disorder syndromes?

The study analyses clinical presentation of language functions of 32 patients with subcortical aphasia induced by stroke. The patients have been divided into three groups according to neuroanatomic localization of the lesion, defined by CT and MRI examination (striato-capsular aphasia, aphasia associated with white matter paraventricular lesions and thalamic aphasia). The following batteries and tests were used: the neurologic examination, CT scan, MRI, Doppler ultrasound, Mini Mental State Examination, Boston Diagnostic Aphasia Examination (BDAE), Boston Naming Test (BNT), Token Test and Verbal Fluency Test. Clinical presentation of subcortical aphasias is characterized with preserved repetition, however, some groups differ by certain specific features of language impairment. Striato-capsular aphasia and aphasia associated with white matter paraventricular lesions are characterized with lack of speech fluency, occurrence of literary paraphasias, mainly preserved comprehension and naming. Thalamic aphasia, however, is characterized with fluent output, impaired comprehension and naming with predominant verbal paraphasias. The specific features of language impairment suggest that subcortical structures contribute to language organization. Considering the results of language tests we presume that the most prominent feature in striato-capsular aphasia is phonetic impairment of language, opposite to thalamic aphasia where lexical-sematic processing seems to be affected.

Association of cocaine- and amphetamine-regulated transcript-immunoreactive elements with thyrotropin-releasing hormone-synthesizing neurons in the hypothalamic paraventricular nucleus and its role in the regulation of the hypothalamic-pituitary-thyroid axis during fasting.

Because cocaine- and amphetamine-regulated transcript (CART) coexists with alpha-melanocyte stimulating hormone (alpha-MSH) in the arcuate nucleus neurons and we have recently demonstrated that alpha-MSH innervates TRH-synthesizing neurons in the hypothalamic paraventricular nucleus (PVN), we raised the possibility that CART may also be contained in fibers that innervate hypophysiotropic thyrotropin-releasing hormone (TRH) neurons and modulate TRH gene expression. Triple-labeling fluorescent in situ hybridization and immunofluorescence were performed to reveal the morphological relationships between pro-TRH mRNA-containing neurons and CART- and alpha-MSH-immunoreactive (IR) axons. CART-IR axons densely innervated the majority of pro-TRH mRNA-containing neurons in all parvocellular subdivisions of the PVN and established asymmetric synaptic specializations with pro-TRH neurons. However, whereas all alpha-MSH-IR axons in the PVN contained CART-IR, only a portion of CART-IR axons in contact with pro-TRH neurons were immunoreactive for alpha-MSH. In the medial and periventricular parvocellular subdivisions of the PVN, CART was co-contained in approximately 80% of pro-TRH neuronal perikarya, whereas colocalization with pro-TRH was found in <10% of the anterior parvocellular subdivision neurons. In addition, >80% of TRH/CART neurons in the periventricular and medial parvocellular subdivisions accumulated Fluoro-Gold after systemic administration, suggesting that CART may serve as a marker for hypophysiotropic TRH neurons. CART prevented fasting-induced suppression of pro-TRH in the PVN when administered intracerebroventricularly and increased the content of TRH in hypothalamic cell cultures. These studies establish an anatomical association between CART and pro-TRH-producing neurons in the PVN and demonstrate that CART has a stimulatory effect on hypophysiotropic TRH neurons by increasing pro-TRH gene expression and the biosynthesis of TRH.

Pineal and habenula calcification in schizophrenia.

Animal data indicate that melatonin secretion is stimulated by the paraventricular nucleus (PVN) of the hypothalamus and that lesions of the PVN mimic the endocrine effects of pinealectomy. Since the PVN lies adjacent to the third ventricle, I propose that periventricular damage, which is found in schizophrenia and may account for the third ventricular dilatation seen on computed tomographic (CT), may disrupt PVN-pineal interactions and ultimately enhance the process of pineal calcification (PC). To investigate this hypothesis, I conducted CT study on the relationship of PC size to third ventricular width (TVW) in 12 chronic schizophrenic patients (mean age: 33.7 years; SD = 7.3). For comparison, I also studied the relationship of PC size to the ventricular brain ratio and prefrontal cortical atrophy. As predicted, there was a significant correlation between PC size and TVW (r pbi = .61, p < .05), whereas PC was unrelated to the control neuroradiological measures. The findings support the hypothesis that periventricular damage may be involved in the process of PC in schizophrenia and may indirectly implicate damage to the PVN in the mechanisms underlying dysfunction of the pineal gland in schizophrenia. In a second study, I investigated the prevalence of habenular calcification (HAC) on CT in a cohort of 23 chronic schizophrenic-patients (mean age: 31.2 years; SD = 5.95). In this sample HAC was present in 20 patients (87%). Since the prevalence of HAC in a control population of similar age is only 15% these data reveal an almost 6-fold higher prevalence of HAC (X2 = 84.01, p < .0001) in chronic schizophrenia as compared to normal controls. The implications of HAC for the pathophysiology of schizophrenia are discussed in light of the central role of the habenula in the regulation of limbic functions.