Final number of Purkinje and other large cells in the chick cerebellum increased by oxygen and by glucose

Abstract

It has been suggested that biogenic amines, in addition to their role as neurotransmitters, may also act as growth factors in the embryo. In the present work the concentrations of serotonin (5-HT), norepinephrine (NE) and dopamine (DA) were first determined in cerebral hemispheres of chick embryo at 10, 12 and 14 days of continuous incubation at 37.5°C (controls). When the incubation on days 7–10 was at 40°C (experimentals), a procedure known to increase brain weight, brain protein content and brain cell number, the concentration of 5-HT in cerebral hemispheres at day 10 (end of neuron proliferation) was significantly increased; this increase persisted at days 12 and 14 but ceased to be significant. No such increases were observed in the concentrations of NE and DA in experimentals at either day 10, 12 or 14. When 5-HT was injected into albumen of eggs at day 7 (37.5°C), cerebral weights, optic lobe weights and cerebral concentrations of 5-HT at day 10 were significantly increased over non-injected controls. Elevated temperature of incubation (40°C) further increased cerebral weight and 5-HT concentration. Cerebral protein contents and the ratios of cerebral protein/ cerebral DNA at day 10 were also significantly increased but cerebral DNA and body weights were unchanged. The optimal doses have been determined. It is concluded that 5-HT may be a growth promoting or regulating factor for embyronal brain.