Olfaction and food intake are interrelated and regulated. In the process of feeding, the metabolic signals in the body and the feeding signals produced by food stimulation are first sensed by the arcuate nucleus of hypothalamus and the nucleus tractus solitarius of brain stem, and then these neurons project to the paraventricular nucleus of hypothalamus. The paraventricular nucleus transmits the signals to other brain regions related to feeding and regulates feeding behavior. In this process, olfactory signals can be transmitted to hypothalamus through olfactory bulb and olfactory cortex to regulate feeding behavior. At the same time, gastrointestinal hormones (ghrelin, insulin, leptin, etc.) and some neurotransmitters (acetylcholine, norepinephrine, serotonin, endocannabinoid, etc.) produced in the process of feeding act on the olfactory system to regulate olfactory function, which in turn affects the feeding itself. This review summaries the research progress of the interaction between olfaction and food intake and its internal mechanism from the aspects of neuronal and hormonal regulation.
Arcuate Nucleus of Hypothalamus/metabolism* ; Feeding Behavior/physiology* ; Hypothalamus ; Paraventricular Hypothalamic Nucleus ; Smell

The nucleus tractus solitarii (NTS) is one of the morphologically and functionally defined centers that engage in the autonomic regulation of cardiovascular activity. Phenotypically-characterized NTS neurons have been implicated in the differential regulation of blood pressure (BP). Here, we investigated whether phenylethanolamine N-methyltransferase (PNMT)-expressing NTS (NTS^PNMT) neurons contribute to the control of BP. We demonstrate that photostimulation of NTS^PNMT neurons has variable effects on BP. A depressor response was produced during optogenetic stimulation of NTS^PNMT neurons projecting to the paraventricular nucleus of the hypothalamus, lateral parabrachial nucleus, and caudal ventrolateral medulla. Conversely, photostimulation of NTS^PNMT neurons projecting to the rostral ventrolateral medulla produced a robust pressor response and bradycardia. In addition, genetic ablation of both NTS^PNMT neurons and those projecting to the rostral ventrolateral medulla impaired the arterial baroreflex. Overall, we revealed the neuronal phenotype- and circuit-specific mechanisms underlying the contribution of NTS^PNMT neurons to the regulation of BP.
Solitary Nucleus/metabolism* ; Blood Pressure/physiology* ; Phenylethanolamine N-Methyltransferase/metabolism* ; Neurons/metabolism* ; Paraventricular Hypothalamic Nucleus/metabolism*

The hypothalamic paraventricular nucleus (PVN) is a central site for integration of the endocrine system and the autonomic nervous system. Despite a number of studies have pointed out the importance of the PVN in the central regulation of cardiovascular functions, the chemical mediators in the PVN responsible for mediating baroreflex are not well understood. In the present study, we used the conscious rats to investigate the possible involvement of glycine (Gly) in PVN in the central regulation of baroreflex induced by intravenous injection of phenylephrine (0.8 mug/0.04 mL, in 3 min). Then, the microdialysis sampling was performed in the PVN and the concentration of Gly in the microdialysate was measured by high performance liquid chromatography (HPLC) combined with electrochemical techniques, and mean arterial pressure (MAP) and heart rate (HR) were recorded simultaneously. Injection of phenylephrine elicited a significant increase (P<0.01) in MAP from the baseline of (99.5+/-14.2) mmHg to the maximum of (149.8+/-19.5) mmHg and a decrease (P<0.01) in HR from the baseline of (400.8+/-33.1) beats/min to the minimum of (273.4+/-40.8) beats/min, respectively. Synchronously, the injection of phenylephrine increased the level of Gly in the microdialysate from the PVN to (162.9+/-27.3)% of the basal level (P<0.05). Perfusion of strychnine (100 mumol/L), an antagonist of Gly receptor, into the PVN enhanced the pressor response and attenuated the bradycardic response during the baroreflex, resulting in a decrease in baroreflex sensitivity (P<0.001). Whereas, the perfusion of Gly (1 mmol/L) into the PVN did not affect the pressor response but enhanced the bradycardic response during the baroreflex, resulting in an increase in baroreflex sensitivity (P<0.001). These results suggest that endogenous Gly in the PVN may act via strychnine-sensitive Gly receptor to produce a facilitative effect on baroreflex.
Animals ; Baroreflex ; drug effects ; Glycine ; pharmacology ; Heart Rate ; Microinjections ; Paraventricular Hypothalamic Nucleus ; physiology ; Phenylephrine ; pharmacology ; Rats

The hypothalamic paraventricular nucleus (PVN) is a crucial region involved in maintaining homeostasis through the regulation of cardiovascular, neuroendocrine, and other functions. The PVN provides a dominant source of excitatory drive to the sympathetic outflow through innervation of the brainstem and spinal cord in hypertension. We discuss current findings on the role of the PVN in the regulation of sympathetic output in both normotensive and hypertensive conditions. The PVN seems to play a major role in generating the elevated sympathetic vasomotor activity that is characteristic of multiple forms of hypertension, including primary hypertension in humans. Recent studies in the spontaneously hypertensive rat model have revealed an imbalance of inhibitory and excitatory synaptic inputs to PVN pre-sympathetic neurons as indicated by impaired inhibitory and enhanced excitatory synaptic inputs in hypertension. This imbalance of inhibitory and excitatory synaptic inputs in the PVN forms the basis for elevated sympathetic outflow in hypertension. In this review, we discuss the disruption of balance between glutamatergic and GABAergic inputs and the associated cellular and molecular alterations as mechanisms underlying the hyperactivity of PVN pre-sympathetic neurons in hypertension.
Animals ; Blood Pressure ; physiology ; Excitatory Postsynaptic Potentials ; physiology ; Humans ; Hypertension ; physiopathology ; Hypothalamus ; physiology ; Neurons ; physiology ; Paraventricular Hypothalamic Nucleus ; physiology

AIMTo investigate the role of motilin in paraventricular nucleus (PVN) of hypothalamus on the regulation of gastric motility and the mechanism.

METHODSImmunohistochemistry and microinjection of motilin into PVN were used to observe motilin neural cells in PVN, the neural path between PVN and dorsal vagal complex (DVC) and the changes of gastric motility in conscious rats.

RESULTS(1) There were motilin immunoreactive-cells in PVN and a significant increase was found in groups of fasting and HCL-perfusion into duodenum. (2) HRP-positive cells were found in PVN after microinjection HRP into dorsal nucleus of vagal nerve. It proved that there was neural relationship between PVN and DVC. (3) The amplitude and frequency of gastric motility increased significantly by microinjection motilin into PVN in conscious rats. The effects produced by motilin could be abolished by vagotomy.

CONCLUSIONAll these results presented imply that motilin in PVN may increase gastric motility through PVN-DVC-Vagal nerve axis.

Animals ; Female ; Gastrointestinal Motility ; physiology ; Hypothalamus ; physiology ; Male ; Motilin ; physiology ; Paraventricular Hypothalamic Nucleus ; physiology ; Rats ; Rats, Wistar

AIMTo study the possibility that responses of fever and discharge of neurons in PVN to intraperitoneal administration of LPS are mediated by vagal afferents.

METHODSRectal temperature of rat was detected by digital temperature detecting instrument. Glass micropipette placed in PVN was used to record unit discharges of neurons in it, before and after LPS was injected into PVN in normal rats and vagotomy rats.

RESULTSThe rectal temperature change value in vagotomy LPS group was significantly decreased compared with that in sham LPS group, and there was striking difference between them (P < 0.05). The discharges of neurons in PVN was increased in the normal rat in response to LPS. The discharges of neurons in PVN had no significant change in the vagotomy rats in response to LPS.

CONCLUSIONThe results indicate that vagus nerve may be one of the pathways of peripheral LPS signal communicating to CNS.

Animals ; Diaphragm ; innervation ; Fever ; chemically induced ; physiopathology ; Lipopolysaccharides ; Male ; Neurons ; physiology ; Paraventricular Hypothalamic Nucleus ; physiopathology ; Rats ; Rats, Wistar ; Vagotomy, Truncal

AIMTo investigate the inhibitory effect of the deep peroneal nerve (DPN) on the cardiovascular responses induced by excitation of the paraventricular nucleus of hypothalamus (PVN) and the role of central nucleus of amygdala (CeA) in this effect.

METHODSCeA was injected by L-glutamate or Kainic acid (KA). The femoral arterial pressure, mean arterial pressure (MAP), electrocardiogram (ECG) and heart rate (HR) of SD rats were recorded while PVN or DPN was electrically stimulated.

RESULTSIt showed that MAP increased when PVN was activated by electrical stimulation. Stimulating contralateral DPN inhibited this pressor response. Ten minutes after microinjection of KA(0.02 mol/L, 100 nl) into ipsilateral CeA, MAP increased for (13.8 +/- 3.2) mmHg when PVN was stimulated. Microinjection of KA into CeA could not only reduce the pressor response elicited by stimulation of PVN for (6.6 +/- 1.6) mmHg (P < 0.05), but also the inhibitory effect of DPN from 51.5% to 32.0% .

CONCLUSIONThe results suggest that central nucleus of amygdala partly mediate the central pressor response induced by stimulation of PVN. The neurons in central nucleus of amygdala are involved in the inhibitory effect of DPN on the above pressor response.

Afferent Pathways ; Amygdala ; physiology ; Animals ; Blood Pressure ; Central Nervous System ; physiology ; Hypothalamus ; physiology ; Paraventricular Hypothalamic Nucleus ; physiology ; Peroneal Nerve ; physiology ; Rats ; Rats, Sprague-Dawley

The role of atrial natriuretic peptide (ANP) in the central regulation of the circulation is known to be a neurotransmitter or a neuromodulator, but its actions on baroreceptor reflex function are not fully resolved. The present study examined the role of ANP (6, 60 ng/0.2 microl) by direct microinjection into the hypothalamic paraventricular nucleus (PVN) in conscious rats. OPC-21268 (0.45 microg/3 microl), an antagonist of the V(1) receptor, was microinjected into the lateral ventricle to examine whether the effect of ANP on baroreflex sensitivity is mediated by vasopressin (VP). ANP significantly increased the baroreflex sensitivity, and OPC-21268 attenuated the increase of baroreflex sensitivity induced by ANP. Intravenous injections of ANP (60 ng/0.04 ml) did not affect baroreflex sensitivity. These results suggest that ANP in the PVN may produce a facilitative effect on baroreflex, and the effect may be via, at least in part, the central vasopressin.
Animals ; Atrial Natriuretic Factor ; pharmacology ; physiology ; Baroreflex ; drug effects ; physiology ; Male ; Microinjections ; Paraventricular Hypothalamic Nucleus ; physiology ; Random Allocation ; Rats ; Rats, Wistar

AIMTo investigate the possible involvement of glutamate(Glu) in the paraventricular nucleus (PVN) in the central regulation of baroreflex.

METHODSThe baroreflex was induced by intravenous injection of phenylephrine in conscious rats, and the extracellular concentration of Glu in the PVN region was measured by microdialysis and high performance liquid chromatography (HPLC) techniques. To determine whether the observed Glu release was involved in the baroreflex, NMDA and non-NMDA receptor antagonists, MK-801 and CNQX, were perfused in the PVN region during baroreflex.

RESULTSDuring baroreflex, the Glu concentration in the PVN region immediately increased to 384.82% +/- 91.77% of basal level (P < 0.01). (2) During baroreflex, direct perfusion of MK-801 and CNQX in the PVN were attenuated the increase of blood pressure and enhanced the decrease of HR (P < 0.01),resulting a significant increase in baroreflex sensitivity (P < 0.01).

CONCLUSIONGlutamate in PVN is involved in central regulation of baroreflex, which may inhibit baroreflex via ionothopic glutamate receptors.

6-Cyano-7-nitroquinoxaline-2,3-dione ; pharmacology ; Animals ; Baroreflex ; drug effects ; physiology ; Dizocilpine Maleate ; pharmacology ; Excitatory Amino Acid Antagonists ; pharmacology ; Male ; Paraventricular Hypothalamic Nucleus ; physiology ; Rats ; Rats, Wistar

OBJECTIVESTo investigate the relationship between penile erection induced by L-arginine in paraventricular nucleus (PVN) and androgen.

METHODSTwenty-four mature male rabbits were randomly divided into three groups which were castrate, castrate with testosterone propionate (T) replacement and pseudo-operation. One month later, the highest intracavernous pressure (ICP) and nitric oxide synthase (NOS) of each PVN tissue were measured after infusing L-arginine into the PVN.

RESULTSThe mean ICPs of the highest values in castrate, castrate given T replacement and pseudo-operation groups were (22.640 +/- 4.747) mmHg, (38.146 +/- 4.907) mmHg and (39.991 +/- 3.068) mmHg, respectively. The mean value of NOS activity of each group were (0.807 +/- 0.188) U/mg.prot, (1.457 +/- 0.293) U/mg.prot and (1.528 +/- 0.204) U/mg.prot, respectively. The ICP and NOS activity in castrate were different statistically from T replacement and pseudo-operation group (both P < 0.01). T replacement group had no statistical difference from pseudo-operation group(P > 0.05).

CONCLUSIONSNitric oxide (NO) is one of the neurotransmitters in PVN particularly relevant for the control of penile erection. Penile erection induced by L-arginine in PVN depends on androgen.

Animals ; Arginine ; pharmacology ; Male ; Nitric Oxide ; physiology ; Paraventricular Hypothalamic Nucleus ; drug effects ; physiology ; Penile Erection ; drug effects ; Pressure ; Rabbits ; Testosterone ; blood ; pharmacology