Robust Reductions of Excess Weight and Hyperphagia by Beloranib in Rat Models of Genetic and Hypothalamic Obesity.

Hypothalamic lesions or deficient melanocortin (MC) signaling via MC4 receptor (MC4r) mutations often lead to hyperphagia and severe treatment-resistant obesity. We tested the methionine aminopeptidase 2-inhibitor beloranib (ZGN-440) in 2 male rat models of obesity, one modeling hypothalamic obesity with a combined medial hypothalamic lesion (CMHL) and the other modeling a monogenic form of obesity with MC4r mutations (MC4r knockout [MC4rKO]). In CMHL rats (age 3 months), postsurgery excess weight gain was significantly inhibited (ZGN-440, 0.2 ± 0.7 g/d; vehicle, 3.8 ± 0.6 g/d; P < 0.001) during 12 days of ZGN-440 treatment (0.1 mg/kg daily subcutaneously) together with a 30% reduction of daily food intake vs vehicle injection. In addition, ZGN-440 treatment improved glucose tolerance and reduced plasma insulin, and circulating levels of α-melanocyte stimulating hormone were increased. Serum lipid levels did not differ significantly in ZGN-440-treated vs vehicle-treated rats. Similar results were found in MC4rKO rats: ZGN-440 treatment (14-21 d) was associated with significant reductions of body weight gain (MC4rKO, -1.7 ± 0.6 vs 2.8 ± 0.4 g/d; lean wild-type controls, -0.7 ± 0.2 vs 1.7 ± 0.7 g/d; ZGN-440 vs vehicle, respectively), reduction of food intake (MC4rKO, -28%; lean controls, -7.5%), and insulin resistance, whereas circulating levels of interleukin-1ß did not change. In both obesity models, body temperature and locomotor activity were not affected by ZGN-440 treatment. In conclusion, the robust reduction of body weight in response to ZGN-440 observed in rats with severe obesity is related to a strong reduction of food intake that is likely related to changes in the central regulation of feeding.

Effects of medial hypothalamic lesions on feeding-induced entrainment of locomotor activity and liver Per2 expression in Per2::luc mice.

Restricted feeding induces anticipatory activity rhythm and also entrains the peripheral circadian clocks, although the underlying brain mechanisms have not been fully elucidated. The dorsomedial hypothalamus (DMH) has been implicated in the regulation of restricted feeding-induced anticipatory activity rhythms (FAA), but the role of the DMH in restricted feeding- induced entrainment of peripheral circadian clocks is still unknown. In the present study, the role of the DMH in entrainment of the peripheral circadian clock was examined using Per2::luciferase knock-in mice. The results indicate that lesions that destroy the large mediobasal hypothalamic (MBH) lesions destroying the DMH, ventrolateral hypothalamus (VMH), and arcuate nucleus (ARC) significantly reduce daily locomotor activity rhythms and FAA formation. In addition, these lesions phase advanced the peak of liver Per2 expression by 2 h when compared to sham-operated mice. Following the administration of MBH lesions, the animals run less and start later in the restricted feeding- induced FAA rhythm but do not have any alterations in the restricted feeding- induced phase shift of the liver Per2 rhythm. These results demonstrate that the hypothalamus, including the MBH, is an important brain area for maintaining the locomotor rhythm and FAA formation. However, it is not necessary for restricted feeding-induced entrainment of the liver clock.

The medial hypothalamic defensive circuit and 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) induced fear: comparison of electrolytic and neurotoxic lesions.

The neural circuits for unconditioned fear to predator odors (e.g., cat fur odor, trimethylthiazoline, TMT) are not well delineated. A putative neural circuit for predator odor fear, the medial hypothalamic defensive circuit (MHDC), consisting of the anterior hypothalamic (AHN), ventromedial hypothalamic (VMH) and dorsal premammillary nuclei (PMd), has been proposed. Electrolytic and ibotenic acid lesions of the PMd have been shown to reduce unconditioned fear in rats presented with either a cat or cat odor. Whether the PMd, AHN and VMH are involved in unconditioned fear to another predator odor derived from fox feces, 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), has not been explored. The present study compared the effects of electrolytic and neurotoxic lesions of MHDC nuclei in rats on unconditioned fear to TMT and shock-induced contextually conditioned fear, as measured by freezing. Electrolytic lesions of the PMd did not reduce TMT-induced freezing, but diminished post-shock and shock-induced contextually conditioned freezing, suggesting a role for the PMd in contextually conditioned fear. In contrast, electrolytic lesions of the AHN and VMH reduced freezing to TMT while not affecting conditioned fear. However, neither NMDA lesions of the AHN nor ibotenic acid lesions of the VMH reduced freezing in shock-induced conditioned or TMT-induced unconditioned fear paradigms. The data suggest that fibers passing through the AHN and VMH, and not cells in the MHDC, mediate unconditioned freezing to the predator odor TMT.

Transplantation of the fetal olfactory placode restores reproductive cycles in female rhesus monkeys (Mucaca mulatta) bearing lesions in the medial basal hypothalamus.

The purpose of this study was to determine whether loss of the reproductive cycle after lesions of the medial basal hypothalamus can be reversed by transplantation of the embryonic olfactory placode (OP) into female rhesus monkeys. Seven adult female rhesus monkeys with regular menstrual cycles received bilateral radiofrequency lesions in the arcuate nucleus and the median eminence. After confirmation of anovulation in these monkeys, four monkeys were stereotaxically implanted with the OP obtained from monkey fetuses on embryonic days 35-36. The remaining three monkeys were similarly implanted with embryonic cerebellum (CB) as a control. Fetuses were delivered by cesarean section, and the OP and CB were immediately dissected out using a stereomicroscope. Fetal tissue was then cut into small pieces (< 1 mm3), mixed with artificial cerebrospinal fluid containing small pieces of Gelfoam, and stereotaxically injected into the infundibular recess of the third ventricle. The recovery of ovulatory cycles in recipient monkeys was observed for at least 6 months; sex skin color changes and menstrual records were obtained daily, and serum samples for LH, estrogen, and progesterone were obtained twice a week. Three of four OP-transplanted monkeys resumed their ovulatory cycles within 2 months, whereas the fourth monkey, an elderly female, failed to recover her cycle. In contrast, none of the three CB-transplanted monkeys resumed ovulatory cycles. Histological examination indicated that 1) lesion scars were present in the median eminence-stalk region as well as the medial basal portion of the arcuate nucleus of all seven brains; and 2) cartilage was present in the third ventricles of the OP-implanted brains. Moreover, immunocytochemical staining revealed that in all OP monkeys, small, round, and immature LHRH-positive cells with fine short processes were found in the third ventricle and/or median eminence-stalk region, whereas no similar LHRH cells were found in CB-transplanted monkeys. It is concluded, therefore, that implantation of LHRH neurons derived from the fetal OP can result in resumption of the ovulatory cycle in female monkeys whose own LHRH pulse-generating mechanisms were impaired. Moreover, the results suggest that LHRH neurons derived from embryonic OP possess the physiological functions necessary for the stimulation of gonadotropin secretion.

Contribuiçäo ao estudo das glândulas submandibulares, após lesäo da eminência média do hipotálamo, em ratos / Study of the submandibular glands following lesion of the hypothalamus middle eminence in rats

Os autores utilizam 65 ratos divididos em 3 grupos: grupo I - controle; grupo II - operaçäo simulante; e grupo III - submetidos a lesäo da eminência média do hipotálamo. Nesses animais procedeu-se à remoçäo cirúrgica das glândulas submandibulares, tendo-se nelas estudado o peso ponderal, assim como as alteraçöes histológicas. A análise dos resultados permitiu concluir que a lesäo da eminência média do hipotálamo ocasionou alteraçöes nas glândulas submandibulares, representadas por diminuiçäo da massa dessas glândulas, acompanhada de alteraçöes morfológicas caracterizadas por hipertrofia dos ácinos, picnose nuclear das células acinosas e aumento da quantidade de ductos granulosos

Body composition and its relation to systemic haemodynamics, fluid volume partitions and energy utilization in rats with bilateral ventromedial hypothalamic lesions.

Body composition and its relationship with intra-arterial pressure, fluid volume partitions and oxygen consumption were studied in male rats four months following ventromedial hypothalamic (VMH) destruction during the static phase of the development of obesity. Compared with sham-operated controls, rats with VMH lesions had a greater body weight which was related to an increased body lipid content and an elevated arterial pressure and total peripheral resistance. Fluid volume distribution was normal and total body oxygen consumption (per unit of body weight) was reduced. Bilateral destruction of the ventromedial hypothalamus was confirmed in each of the rats studied and no relationship could be demonstrated between the lesion size and the magnitude of haemodynamic changes. It is concluded that the increased arterial pressure observed in obese VMH lesioned rats was directly related to an elevated total body lipid content.

Neonatal brain damage and recovery: intraventricular injection of NGF at time of injury alters performance of active avoidance.

Rats were given lesions of either the ventromedial hypothalamus (VMH) or septal nucleus at 7 days of age and then were tested repeatedly in an active avoidance task (A.A.) from 20 to 80 days. VMH rats were consistently impaired on the A.A. task beginning at 40 days of age. The animals with septal lesions performed the A.A. task consistently better than VMH or control animals throughout the entire test period, the septal syndrome becoming more pronounced as the rats reached maturity. In intact rats a single, intraventricular injection of NGF given at 7 days of age resulted in a greater reactivity, especially as the rats approached maturity. NGF, given at time of surgery, also improved performance of the A.A. task in VMH-damaged rats tested at 40-80 days. In rats given septal lesions, NGF treatment at time of injury attenuated the septal syndrome of improved A.A. performance. The data indicate that NGF treatment, given to neonatal rats, can produce long-lasting effects on CNS functions and can contribute to functional recovery from brain lesions.

Histological survey of the healing process on tooth extraction wounds in rats after hypothalamic median eminence lesion

Foi estudado histologicamente em ratos lesados na eminência média do hipotálamo, o processo de reparo em feridas de extraçäo dental, seguido de um grupo-controle. A extraçäo dental foi realizada imediatamente após a verificaçäo da eficiência da lesäo e o sacrifício dos animais efetuado aos 3, 6, 9, 12, 18 e 21 dias pós-extraçäo. Nossos resultados mostraram que até o 6§ dia näo houve alteraçäo no processo de reparo alveolar. No período intermediário, do 9§ ao 12§ dia, foi verificado um atraso discreto na reparaçäo alveolar dos animais do grupo lesado. O resultado mais significativo ocorreu nos períodos de 18 e 21 dias, com um atraso no processo de reparo do alvéolo, principalmente em sua área central e nos terços cervical, médio e apical. Essas detecçöes levam-nos a concluir que, embora a lesäo tenha afetado o funcionamento hipofisário, em termos de neoformaçäo óssea, a manifestaçäo dessa disfunçäo aparece após um período aproximado de 11 dias

Localization of inhibitory mechanisms to aggressiveness in the medial hypothalamus.

Release of aggressive reactions was studied by placing a small lesion on the medial hypothalamus in the rat with previous massive destruction on the contralateral side of the hypothalamus. A set of tests for reactivity to provocations was applied to rats before the operation, after the unilateral lesion, and once more after the bilateral lesions. Bilateral lesions were accomplished in 53 rats. None of them increased food intake even though the ventromedial region was involved in many cases. Only 7 developed signs of aggressiveness. The unique histological feature of the animals showing aggressiveness was that the lesions were confined to the posterior hypothalamus usually sparing the ventromedial nucleus and were close to the base. It was suggested that the lesions might have interrupted the fibers projecting to the midbrain mechanisms for control of emotional reactivity.