The expression of cholecystokinin and vasopressin binding sites in the developing mammalian brain: a comparative study

All mammalian neonates are equipped with behavioral and physiological strategies to maintain homeostasis. The central nervous system (CNS) controls most aspects of homeostasis in the adult mammal, and presumably in the neonate as well, but the anatomical and physiological pathways involved may differ considerably between neonates and adults. Neurogenesis is considered a prenatal process in most mammals. However, in the Brazilian opossum, Monodelphis domestica, neurons are still being produced in the forebrain after birth. Therefore, Brazilian opossum newborns cannot regulate homeostasis at the forebrain level, although, in the adult, the forebrain consists of control centers for food intake and water balance. The Brazilian opossum provides an excellent mammalian model to study CNS adaptations for neonatal existence. In addition, the comparison of Eutherian and Metatherian brain systems can provide information on conserved pathways, and those that are specific for Metatherian survival;Because the forebrain of the Brazilian opossum is still forming at birth, we predict that hindbrain nuclei may be involved in the regulation of nutrient and fluid intake. Cholecystokinin (CCK) is involved in the regulation of food intake. Arginine vasopressin (AVP) plays a major role in fluid regulation. The purpose of the studies described in this dissertation was to focus on the expression of cholecystokinin and vasopressin binding sites in the neonatal Metatherian and Eutherian brain, with attention being paid to those brainstem nuclei that could potentially be involved in the regulation of nutrient or fluid intake;We found that both CCK and AVP binding sites are expressed transiently in the facial motor nucleus (FMN) of the neonatal rat, and CCK binding sites are expressed transiently in the FMN of the neonatal Brazilian opossum as well. As the FMN controls facial musculature, it is intimately involved in fluid and nutrient intake behavior in neonates. The transient expression of binding sites in this region suggests that cholecystokinin may be regulating nutrient intake at the brainstem level in mammalian neonates. The transient expression of vasopressin binding sites only in the neonatal rat facial may indicate that the regulation of water balance in neonates is controlled by different pathways in these two species

Two Types of Burst Firing in Gonadotrophin‐Releasing Hormone Neurones

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92106/1/j.1365-2826.2012.02313.x.pd

The expression of cholecystokinin and vasopressin binding sites in the developing mammalian brain: a comparative study

All mammalian neonates are equipped with behavioral and physiological strategies to maintain homeostasis. The central nervous system (CNS) controls most aspects of homeostasis in the adult mammal, and presumably in the neonate as well, but the anatomical and physiological pathways involved may differ considerably between neonates and adults. Neurogenesis is considered a prenatal process in most mammals. However, in the Brazilian opossum, Monodelphis domestica, neurons are still being produced in the forebrain after birth. Therefore, Brazilian opossum newborns cannot regulate homeostasis at the forebrain level, although, in the adult, the forebrain consists of control centers for food intake and water balance. The Brazilian opossum provides an excellent mammalian model to study CNS adaptations for neonatal existence. In addition, the comparison of Eutherian and Metatherian brain systems can provide information on conserved pathways, and those that are specific for Metatherian survival;Because the forebrain of the Brazilian opossum is still forming at birth, we predict that hindbrain nuclei may be involved in the regulation of nutrient and fluid intake. Cholecystokinin (CCK) is involved in the regulation of food intake. Arginine vasopressin (AVP) plays a major role in fluid regulation. The purpose of the studies described in this dissertation was to focus on the expression of cholecystokinin and vasopressin binding sites in the neonatal Metatherian and Eutherian brain, with attention being paid to those brainstem nuclei that could potentially be involved in the regulation of nutrient or fluid intake;We found that both CCK and AVP binding sites are expressed transiently in the facial motor nucleus (FMN) of the neonatal rat, and CCK binding sites are expressed transiently in the FMN of the neonatal Brazilian opossum as well. As the FMN controls facial musculature, it is intimately involved in fluid and nutrient intake behavior in neonates. The transient expression of binding sites in this region suggests that cholecystokinin may be regulating nutrient intake at the brainstem level in mammalian neonates. The transient expression of vasopressin binding sites only in the neonatal rat facial may indicate that the regulation of water balance in neonates is controlled by different pathways in these two species.</p

Age Affects Spontaneous Activity and Depolarizing Afterpotentials in Isolated Gonadotropin-Releasing Hormone Neurons

Neuronal activity underlying the pulsatile secretion of GnRH remains poorly understood, as does the endogenous generation of such activity. It is clear that changes at the level of the hypothalamus are taking place during reproductive aging, yet virtually nothing is known about GnRH neuronal physiology in aging and postreproductive animals. In these studies, we performed cell-attached and whole-cell recordings in GnRH-enhanced green fluorescent protein neurons dissociated from young (3 months), middle-aged (10 months), and old (15–18 months) female mice. All mice were ovariectomized; half were estradiol replaced. Neurons from all ages fired spontaneously, most in a short-burst pattern that is characteristic of GnRH neuronal firing. Membrane characteristics were not affected by age. However, firing frequency was significantly reduced in neurons from old animals, as was spike patterning. The amplitude of the depolarizing afterpotential, evoked by a 200-msec current pulse, was significantly smaller in aged animals. In addition, inward whole-cell currents were reduced in estradiol-treated animals, although they were not significantly affected by age. Because depolarizing afterpotentials have been shown to contribute to prolonged discharges of activity after a very brief excitatory input, a decreased depolarizing afterpotential could lead to attenuated pulses in older animals. In addition, decreases in frequency and pattern generation could lead to improper information coding. Therefore, changes in the GnRH neuron during aging could lead to dysregulated activity, potentially resulting in the attenuated LH pulses observed in the transition to reproductive senescence