The voltage-gated calcium channel is composed of a poreforming ␣ 1 subunit and several regulatory subunits: ␣ 2 ␦, ␤, and ␥. We report here the identification of a novel ␣ 2 ␦ subunit, ␣ 2 ␦-4, from the expressed sequence tag database followed by its cloning and characterization. The novel ␣ 2 ␦-4 subunit gene contains 39 exons spanning about 130 kilobases and is colocalized with the CHCNA1C gene (␣ 1C subunit) on human chromosome 12p13.3. Alternative splicing of the ␣ 2 ␦-4 gene gives rise to four potential variants, a through d. The open reading frame of human ␣ 2 ␦-4a is composed of 3363 base pairs encoding a protein with 1120 residues and a calculated molecular mass of 126 kDa. The ␣ 2 ␦-4a subunit shares 30, 32, and 61% identity with the human calcium channel ␣ 2 ␦-1, ␣ 2 ␦-2, and ␣ 2 ␦-3 subunits, respectively. Primary sequence comparison suggests that ␣ 2 ␦-4 lacks the gabapentin binding motifs characterized for ␣ 2 ␦-1 and ␣ 2 ␦-2; this was confirmed by a [ 3 H]gabapentin-binding assay. In human embryonic kidney 293 cells, the ␣ 2 ␦-4 subunit associated with Ca V 1.2 and ␤ 3 subunits and significantly increased Ca V 1.2/␤ 3 -mediated Ca 2ϩ influx. Immunohistochemical study revealed that the ␣ 2 ␦-4 subunit has limited distribution in special cell types of the pituitary, adrenal gland, colon, and fetal liver. Whether the ␣ 2 ␦-4 subunit plays a distinct physiological role in select endocrine tissues remains to be demonstrated.

The effects of prolonged bicuculline-induced seizures on cerebral blood flow and metabolism were determined in paralyzed, mechanically ventilated neonatal dogs. Transient changes occurring early in the course of status epilepticus included significant arterial hypertension, hypocarbia, elevation of plasma norepinephrine levels, and decline in brain glucose concentration. Cerebral blood flow remained elevated throughout the 45 minutes of seizure. Determination of cerebral metabolite values by in vivo phosphorus 31 nuclear magnetic resonance spectroscopy and by in vitro enzymatic analysis of frozen brain samples showed significant decreases in the level of phosphocreatine and relatively less change in ATP values. Progressive intracellular acidosis occurred, coincident with elevation of brain lactate concentrations. We conclude that the physiological and metabolic alterations that occur during prolonged seizures are not uniform, but change with time. Any hypothesis advanced to explain the mechanism of neuronal injury during prolonged seizures must take into account these temporally related changes.

Summarytional 2 0 4 samples of arterial blood were obtained hourly forThe acute systemic and neuropathologic effects of E. coli endotoxin were determined in neonatal dogs. Administration of sublethal (LDo), moderate (LD50), or lethal (LDlo0) doses of endotoxin produced significant arterial hypotension, metabolic (lactic) acidosis, and hypoglycemia. Neuropathologic changes consisted of widespread inflammation in both grey and white matter; however, necrotic lesions were found only in forebrain white matter.determination ofplasma glucose and lactate levels by fluorometric analysis according to the method of Lowry and Passoneau (19). Body temperature was monitored by means of a rectal thermocouple (Yellow Springs) and maintained by a servo-controlled heating lamp. After insertion of the catheter, halothane was withdrawn and the animals allowed to spbntaneously breathe room air. The wound was sutured and periodically infiltrated with xylocaine, 1%. A low (LDo), moderate (LD~o), or high (LDIoo) Bacterial infections in the human infant are an important cause of subsequent mental retardation, cerebral palsy, and epilepsy (18,22,23,25). The morbidity and mortality associated with perinatal bacterial infections have been attributed to bacterial endotoxin, a lipopolysaccharide component of the bacterial cell wall. Because administration of endotoxin to laboratory animals mimics human septicemia (1,4,8,14), the systemic and neuropathologic disturbances induced by endotoxin are of considerable interest.Studies by Gilles et al. (12) have shown that administration of E. coli endotoxin to newborn kittens produces extensive brain injury. The acute systemic changes occurring during neonatal endotoxemia have not been described in detail. We, therefore, undertook a series of experiments in neonatal dogs to determine the acute neuropathologic changes occurring during endotoxemia as well as the critical physiologic and and metabolic parameters (blood pressure, heart rate, arterial blood gases, glucose, and lactate levels), which might be associated with those neuropathologic changes. Although these systemic parameters have not been studied during endotoxemia in the neonatal dog, they have been shown to be important predictors of mortality in the endotoxintreated adult dog (5,9,17,20). MATERIALS AND METHODSDose-response curve. Mongrel dogs, 1-10 days of age, were selected because their state of neurologic development at birth resembles that of the human infant of approximately 34-40 wk gestation (16). Trials were conducted in 16 animals to determine the dose of E. coli endotoxin that would result in 0, 50, and 100% mortality when injected subcutaneously. A lyophilized preparation of endotoxin from E. coli 055:B5 (Difco Laboratories) was chosen because this organism is a pathogen for human neonates, may be transmitted by nursery personnel (28), and has been previously used in neuropathologic experiments (12).Systemic responses to graded endotoxemia. The physiologic and metabolic responses of the animals were examined before and after ...