Using c-Fos immunocytochemistry to identify forebrain regions that may inhibit maternal behavior in rats.

Evidence indicates there is a neural system that inhibits maternal behavior in virgin rats. It has been suggested that pregnancy hormones promote the onset of maternal behavior by reducing the behavioral influence of this system. The authors used c-Fos immunocytochemistry to identify brain regions more activated by pup exposure in nonmaternal rats than in maternal rats. Previous experiments indicated that some of these regions, such as the posterodorsal medial amygdala and several medial hypothalamic sites, inhibit maternal behavior. For others, such as the ventral lateral septum, dorsal premammillary nucleus, and principal bed nucleus of the stria terminalis, this is the first indication that they could also inhibit maternal responding. These regions have previously been implicated in promoting defensive behaviors, consistent with the finding that nonmaternal rats actively avoid pups. These findings suggest the existence of a neural circuit through which pup exposure could promote defensive responses in virgin rats, and how pregnancy hormones could reduce such activity to stimulate maternal behavior.

Expression of intracellular progesterone receptors in rat brain during different reproductive states, and involvement in maternal behavior.

Progesterone is one of a complex of hormones which influences the occurrence of maternal behavior in rats. The present study provides information on progesterone's mechanism and possible neural site(s) of action with respect to maternal responsiveness. Progesterone can exert cellular effects by acting on membrane receptors or by acting on intracellular receptors. In the first experiment we show that RU 486 can antagonize progesterone's inhibitory effect on maternal behavior. Since RU 486 acts as an antagonist to progesterone's action at its intracellular receptor, these results support the involvement of that receptor in maternal behavior control. The second experiment employs immunocytochemical techniques to detect the number of cells in various forebrain regions which contain intracellular progesterone receptors during different reproductive states. The number of cells which contained progesterone receptors was higher toward the end of pregnancy (progesterone is presumably exerting its effects on maternal behavior at this time) when compared to either early pregnancy or lactation in the following forebrain regions: anteroventral periventricular nucleus of the preoptic area; medial preoptic area; ventral part of the bed nucleus of stria terminalis; ventrolateral division of the ventromedial nucleus; arcuate nucleus; anterior paraventricular nucleus of the hypothalamus; and medial amygdala. The possible involvement of these regions as a site or sites where progesterone might exert its effects on maternal behavior is discussed.

Neurologic outcome of early versus late surgery for cervical spinal cord injury.

STUDY DESIGN: A prospective analysis evaluating neurologic outcome after early versus late surgery for cervical spinal cord trauma. OBJECTIVES: The study was conducted to determine whether neurologic and functional outcome is improved in traumatic cervical spinal cord-injured patients (C3-T1, American Spinal Injury Association grades A-D) who had early surgery (<72 hours after spinal cord injury) compared with those patients who had late surgery (>5 days after spinal cord injury). SUMMARY OF BACKGROUND DATA: There is considerable controversy as to the appropriate timing of surgical decompression and stabilization for cervical spinal cord trauma. There have been numerous retrospective studies, but no prospective studies, to determine whether neurologic outcome is best after early versus late surgical treatment for cervical spinal cord injury. METHODS: Patients meeting appropriate inclusion criteria were randomized to an early (<72 hours after spinal cord injury) or late (>5 days after spinal cord injury) surgical treatment protocol. The neurologic and functional outcomes were recorded from the acute hospital admission to the most recent follow-up. RESULTS: Comparison of the two groups showed no significant difference in length of acute postoperative intensive care stay, length of inpatient rehabilitation, or improvement in American Spinal Injury Association grade or motor score between early (mean, 1.8 days) versus late (mean, 16.8 days) surgery. CONCLUSIONS: The results of this study reveal no significant neurologic benefit when cervical spinal cord decompression after trauma is performed less than 72 hours after injury (mean, 1.8 days) as opposed to waiting longer than 5 days (mean, 16.8 days).

Microinjection of the tachykinin neuropeptide K into the ventromedial hypothalamus disrupts the hormonal onset of maternal behavior in female rats.

The medial amygdala exerts an inhibition of maternal behavior in virgin rats, but neither the site to which it projects to exert this effect nor the neurotransmitter used in such a pathway is known. There is also evidence that the ventromedial nucleus of the hypothalamus exerts an inhibition of maternal behavior, and the medial amygdala projects to this nucleus, suggesting that it may receive a projection from the medial amygdala which is inhibitory for maternal behavior. Tachykinin injection into the hypothalamus inhibits reproductive behavior in male rats, and there is a tachykininergic projection from the medial amygdala to the ventromedial hypothalamus. Consequently, the present study was conducted to evaluate the hypothesis that the tachykinin neuropeptide K can inhibit maternal behavior after injection into the ventromedial hypothalamus. Female rats were primed to be maternal by pregnancy termination and estrogen injection. Four doses of the peptide (279 pmol, 186 pmol, 116 pmol, and 66 pmol) were bilaterally injected into the ventromedial hypothalamus, and all were effective in delaying the onset of maternal behavior. Evidence that neuropeptide K disrupts maternal behavior in animals that have already begun to be maternal is also presented. Site specificity of neuropeptide K's effect to within the region of the ventromedial hypothalamus was supported, as injection into the mediodorsal thalamus was without effect. Some possibly relevant neuroendocrine effects are addressed, as well as the possibility that tachykinins may act within the ventromedial hypothalamus to promote virgin female rats' fear of pup odors.

Children and smoking. A review.

Cigarette smoking is associated not only with significant premature mortality but also with much chronic ill health. Health educators have an important responsibility to dissuade the young from becoming smokers. This paper reviews current information on the topic of children and smoking and offers some specific antismoking strategies.