Blockade of ovulation and release of LH in the rat by electrochemical stimulation of the frontal lobe cortex

Distribution of the neuronal inputs to the ventral premammillary nucleus of male and female rats

The ventral premammillary nucleus (PMV) expresses dense collections of sex steroid receptors and receptors for metabolic cues, including leptin, insulin and ghrelin. The PMV responds to opposite sex odor stimulation and projects to areas involved in reproductive control, including direct innervation of gonadotropin releasing hormone neurons. Thus, the PMV is well positioned to integrate metabolic and reproductive cues, and control downstream targets that mediate reproductive function. In fact, lesions of PMV neurons blunt female reproductive function and maternal aggression. However, although the projections of PMV neurons have been well documented, little is known about the neuronal inputs received by PMV neurons. To fill this gap, we performed a systematic evaluation of the brain sites innervating the PMV neurons of male and female rats using the retrograde tracer subunit B of the cholera toxin (CTb). In general, we observed that males and females show a similar pattern of afferents. We also noticed that the PMV is preferentially innervated by neurons located in the forebrain, with very few projections coming from brainstem nuclei. The majority of inputs originated from the medial nucleus of the amygdala, the bed nucleus of the stria terminalis and the medial preoptic nucleus. A moderate to high density of afferents was also observed in the ventral subiculum, the arcuate nucleus and the ventrolateral subdivision of the ventromedial nucleus of the hypothalamus. Our findings strengthen the concept that the PMV is part of the vomeronasal system and integrates the brain circuitry controlling reproductive functions.

Three-dimensional stereotactic surface projection study of orthostatic hypotension and brain perfusion image in Parkinson's disease

OBJECTIVE

To compare brain perfusion image using three-dimensional stereotactic surface projection (3D-SSP) analysis of N-isopropyl-p-123I iodoamphetamine (123I-IMP) single photon emission computed tomography (SPECT) between patients with Parkinson's disease with orthostatic hypotension and those without orthostatic hypotension.

MATERIALS AND METHODS

Fifteen patients with Parkinson's disease and orthostatic hypotension and 13 patients with Parkinson's disease without orthostatic hypotension were studied. We compared brain perfusion image between the two groups by 3D-SSP.

RESULTS

Bilateral anterior cingulate gyrus perfusion of the patients with orthostatic hypotension was significantly decreased compared to that of the patients without orthostatic hypotension.

CONCLUSIONS

The disorder of anterior cingulate gyrus may participate in the autonomic failure in Parkinson's disease.

Changes in direct current (DC) potentials and infra-slow EEG oscillations at the onset of the luteinizing hormone (LH) pulse

An essential function of the neuroendocrine system lies in the coordination of hypothalamo-pituitary secretory activity with neocortical neuronal activity. Cortical direct current (DC) potential shifts and EEG were monitored in conjunction with the circulating concentration of luteinizing hormone (LH) in humans while asleep to assess a hypothalamic-neocortical interaction. The onset of an LH pulse was accompanied (i) at frontocortical locations by a transient positive DC potential shift of approximately 3 min duration and peak amplitude 50 microV; (ii) at frontal and central locations by an increase in power of infra-slow EEG oscillations for periodicities between 64 and 320 s. Results uniquely demonstrate a coupling of hypothalamo-pituitary activity with regulation of neocortical excitability.

Convergent prefrontal cortex and mamillary body projections to the medial pontine nuclei: a light and electron microscopic study in the rat

To study the convergence of medial prefrontal cortex and mamillary body projections to the medial pontine nuclei, light and electron microscopic, neuroanatomical, tract-tracing experiments were performed. Injections of horseradish peroxidase conjugated to wheat germ agglutinin (WGA-HRP), biotin conjugated to dextran (BD), or rhodamine conjugated to dextran (RD) were made individually or in combinations into the cerebral cortex, hypothalamus, or pons. In addition, injections of WGA-HRP into the medial prefrontal cortex and electrolytic lesions of the mamillary body were made to study the synaptology of afferent projections to the pontine nuclei. In the light microscopic studies, injections of WGA-HRP into the rostromedial pontine nuclei produced dense, retrograde labeling both in the dorsal peduncular area of the medial prefrontal cortex and in the medial mamillary nucleus, pars medialis. Injections of the anterograde tracers BD and RD into the medial prefrontal cortex and the medial mamillary nuclei, respectively, resulted in partially overlapping terminal fields in the rostromedial pontine nuclei. In the electron microscopic studies, injections of WGA-HRP into the dorsal peduncular area and electrolytic lesions of the mamillary body produced anterogradely labeled axon terminals and degenerating axon terminals that synapsed on the same dendrites or neuronal somata in the rostromedial pontine nuclei. The results demonstrate that the medial prefrontal cortex and the medial mamillary nuclei have partially overlapping projections to the rostromedial pontine nuclei and implicate precerebellar relay nuclei in the integration of limbic and/or autonomic functions mediated by convergent projections from the cerebral cortex and the hypothalamus.

Participation of the olfactory system in the control of approach behavior of the female rat to the male

The amounts of time spent by females in the sector of an open field close to the cage housing a normal male or a castrated male were measured in order to quantitate the tendency of the female to reach physical proximity to a sexually active male (androtropism). Intact proestrous or ovariectomized females primed with 100 micrograms of estradiol benzoate/kg b. wt. (EB) or EB plus 2 mg progesterone/kg b. wt. (P) spent significantly more time close to the sexually active (intact) male than in the proximity of the orchidectomized male. In order to determine whether olfactory clues were sufficient for female rats to distinguish between intact and castrated males, the males were removed from the stimulus cages, leaving the soiled bedding in place. Ovariectomized rats primed with EB or EB plus P clearly preferred proximity to the cage where the intact male had been living. No preference was evident after transection of olfactory nerves in proestrous rats or in ovariectomized rats primed with EB plus P. Resection of the vomeronasal organ also suppressed preference. These results indicate that olfactory input is necessary and sufficient for androtropism to occur, and suggest that the accessory olfactory system is involved in the analysis of olfactory signals used by female rats to identify the endocrine status of prospective sexual partners. In a different group of animals, it was demonstrated that destruction of the posteromedial cortical amygdaloid nucleus also suppressed preference for the intact male. It is proposed that this structure serves as a relay station for the analysis and integration of olfactory input significant for the motivational control of sexual behavior in the female rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of unilateral decortication on beta-adrenergic receptors in the remaining cortex and in the hypothalamus of female rats

Many experiments have been performed to evaluate the physiological role of catecholaminergic mechanisms in gonadotropin release. The purpose of the present study was to determine the concentration of beta-adrenoreceptors in the remaining (right) cerebral cortex and in right and left hypothalamic halves of hemi-decorticated female rats which exhibited elevated plasma gonadotropin levels as observed previously. The density of beta-receptors was measured using a high-affinity beta-adrenergic ligand, iodocyanopindolol (ICYP). Scatchard estimates were obtained for maximum binding (Bmax fmol/mg of tissues) from pooled cerebral cortical and hypothalamic tissue of animals under several experimental conditions after hemi-decortication and sham operation. There was an increase in beta-adrenoreceptor density in the remaining (right) cerebral cortex at all times examined in hemi-decorticate in comparison with the sham-operated animals (7 days, +10.9%; 21 days, +8.4%; 90 days, +22%; and 90 days plus ovariectomy, +34.8%). The number of beta-adrenoreceptors in the right hypothalamic half in hemi-decorticates decreased at 21 days (-42.20%) and then increased at 90 days (+76.63%) and 90 days plus ovariectomy (+51.75%) when compared with the left hypothalamic half. At the same time there were no significant changes in the sham-operated animals when comparing the receptor density in the right and left hypothalamic halves, respectively. Thus, our results suggest a direct or indirect adrenergic pathway by which the left cortex can influence the right cortex and a crossed pathway to the contralateral hypothalamus changing adrenergic activity which can alter the beta-adrenergic receptor binding capacity in the hypothalamus.

The topographical organization of neurons in the rat medial frontal, insular and olfactory cortex projecting to the solitary nucleus, olfactory bulb, periaqueductal gray and superior colliculus

In 19 rats two different retrograde tracers (Fast Blue, Diamidino Yellow, Rhodamine-labeled latex microspheres, or wheat germ agglutinin conjugated with HRP) were injected into the solitary nucleus (NTS) and either the olfactory bulb (OB), periaqueductal gray (PAG) or superior colliculus (SC). The pattern of retrogradely labeled neurons in the medial frontal, insular and olfactory cortices was examined to determine the topographical organization of the cell populations projecting to these subcortical targets and the extent to which they overlapped. In the medial frontal cortex (MFC) SC projections originated most dorsally, while NTS and OB projections originated most ventrally and exhibited slight overlap. PAG projections originated from virtually the entire MFC and overlapped with cells projecting to the OB, NTS and SC. These results are consistent with the role of dorsal MFC as the rat's frontal eye field and the ventral MFC as a visceral motor area. Laterally, in the insular cortex there was virtually complete overlap between cells projecting to the NTS and PAG. The extensive overlap of PAG projections with NTS projections medially and laterally and with SC projections medially suggests the PAG is involved in a variety of brain visceral and somatic functions. In the piriform cortex there was overlap between cells projecting to the OB and cells projecting to the SC; the cells projecting to the SC were located in the endopiriform nucleus, and may provide a substrate for orienting responses to odors.

Sodium chloride intake following electrochemical stimulation of the frontal lobe cortex in the rat

The effect of stimulation of the medial surface of the cerebral cortex on the intake of sodium chloride (NaCl) solution was studied in male rats which were depleted of sodium by peritoneal dialysis (p.d.). Electrochemical stimulation (anodic d.c.) was applied through monopolar stainless-steel electrodes chronically implanted in the unanaesthetized freely-behaving animal. Stimulation (100 microA/30 sec,) of the anterior cingulate cortex in its dorsal and ventral portions, 24 hr after p.d. decreased NaCl intake by about 30% compared with pre-stimulation intake in the same animal. An opposite behavior was observed after electrochemical stimulation of the superficial layers of the pre-limbic area. A significant sodium intake occurred when the stimulus was applied 5 hr after p.d. at a time when the sodium appetite was still not evident. However, stimulation applied 24 hr after p.d. gave no significant difference from control. The degree of stimulation exerted by the pre-limbic area on NaCl intake was proportional to the amount of current applied. The results of the present study indicate that the frontal lobe cortex of the brain has a dual effect on the preference for sodium intake in sodium depleted rats, with the cingulate area being inhibitory and the pre-limbic area being facilitatory.