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The controversial hypothesis that intraspinal sprouting by dorsal root axons promotes reinnervation of partially denervated neurons caudal to a low thoracic cord hemisection was re-investigated in rats using quantitative immunohistochemical analysis of the neural specific growth-associated protein B-50 (GAP-43) at postoperative survival times of 3, 10, 21, 42, and 90 days. The lack of increase in B-50-immunoreactivity in all segments below the hemisection at all survival times does not support the concept of intraspinal sprouting following the removal of supraspinal descending pathways.

Vasoactive intestinal polypeptide (VIP) immunoreactivity in the upper spinal dorsal horn is markedly increased after transection, crush or vinblastine treatment of the ipsilateral, segmentally related peripheral nerve. After regeneration of the peripheral nerve, VIP disappears from the upper dorsal horn. Transection-induced VIP increase is abolished by rhizotomy. It is concluded that the expression of VIP is restricted by factor(s) carried by retrograde axoplasmic transport to dorsal root ganglion cells.

The actions of calcitonin gene-related peptide (CGRP) were investigated on 9- to 14-day-old astrocyte cultures obtained from the cerebra of 1- to 2-day-old rats. The morphological appearance of the cells was monitored by immunofluorescent staining of glial fibrillary acidic protein (GFAP), and the concentration of adenosine 3',5'-monophosphate (cyclic AMP) was measured in the cultures using radioimmunoassay. CGRP induced a morphological change in cultured astrocytes from rat brain. Flat, polygonal cells positive for GFAP became multipolar with many processes. In addition, CGRP stimulated the accumulation of cyclic AMP by up to 30-fold, half maximal stimulation being obtained at CGRP concentrations in the range 100-300 nM. These data provide evidence for the presence of functional CGRP receptors on astrocytes and suggest a role for CGRP as an intercellular messenger controlling the state of differentiation and activation of astroglial cells.

A method has been devised for long-term culturing of sensory ganglion cells, free of non-neuronal cells. After enzymatic-mechanical disaggregation of embryonic chick sensory ganglia the cell suspension is plated in dispersed cell culture. After 2-3 weeks in culture neurons and satellite cells re-associate in a histiotypic fashion. Partial or complete elimination of non-neuronal cells is achieved by treatment of the cultures with fluorodeoxyuridine. The glia-deprived neurons are electrophysiologically active and can be maintained in cell culture for more than 5 months.

Transection of the facial nerve leads to a glial response within its central nucleus of origin. Concomitant with a proliferation of satellite microglial cells an astrocytic reaction is also seen. In the present study light and electron microscopic autoradiography were performed in order to clarify whether only microglial cells undergo mitosis following facial nerve axotomy or if astrocytes also divide. Our results provide the first electron microscopical autoradiographic evidence for the labelling of endogenous microglial cells. We suggest that microglial cells are the only proliferating element during this process in the rat facial nucleus.

The effect of the xanthine derivatives theophylline and propentofylline (HWA 285) on postischemic selective nerve cell damage was studied in the hippocampus of the Mongolian gerbil and assessed by measuring the decrease of Nissl staining in the CA1 area. Theophylline administered 15 min prior to a 2-min period of bilateral carotid occlusion led within 4 days to a marked damage of CA1 neurons which was not seen in untreated animals. Prolongation of the ischemic period to 5 min led to the same degree of damage in theophylline-treated and untreated animals revealing that the protective power of endogenous adenosine is limited. In contrast to theophylline, treatment with propentofylline (10 mg/kg, i.p.) antagonized cell death; such a protection by propentofylline was also achieved after 5 min ischemia in animals treated with theophylline. This indicates that propentofylline does not exert its protective effect via adenosine-mediated mechanisms.

Five monoclonal antibodies specific for rat monocytes/macrophages were used to characterize macrophages/microglia bulk isolated from neonatal and adult rat brain. The majority of brain macrophages was positive for all antibodies tested with minor differences between cultures derived from developing and mature central nervous tissue. These results contrast in vivo findings indicating that most antigens of peripheral macrophages are absent from resting, activated and phagocytic microglia in situ. We conclude that brain macrophages/microglia newly express antigens of the myelomonocytic lineage when in culture and that cultured brain macrophages may be derived from different types of precursor cells normally present within the CNS.

The rat facial nerve was transected and the retrograde reaction studied in the facial nucleus using light and electron microscopic immunohistochemistry and radioimmunoassay for calcitonin gene-related peptide (CGRP). An initial increase of CGRP-immunoreactivity (IR) was noted at 15 h after axotomy, thereafter CGRP-IR continued to rise to maximal levels around day 6 after which it gradually decreased and reached normal levels again after 5-6 weeks. Immunoreactive CGRP was found to fill the perikarya of facial motoneurons extending into dendrites and axons. Possible functional implications of CGRP as a neuroregulatory molecule during nerve regeneration are discussed.

The relationship between the heterogeneous distribution of A-1 adenosine receptors and the capacity of adenosine to depress neuronal activity was examined in the rat hippocampus. Utilizing autoradiographic techniques, the distribution of A-1 adenosine receptors was assessed by the binding of [3H]cyclohexyladenosine ([3H]CHA) to cryostat sections of rat brain. The apical dendritic region of CA1 showed a differential distribution of adenosine receptors between the stratum radiatum and stratum lacunosum/moleculare. The physiological relevance of this binding difference was studied in the hippocampal slice by examining the capacity of adenosine to depress evoked potentials in these two strata. It was observed that the receptor differences correlated with differential sensitivities to adenosine modulation of the evoked potentials. These data suggest that receptor density, as shown by binding techniques, may provide not only a qualitative but also a quantitative map of the sites of adenosine action.

A marked depression of evoked CA1 potentials was observed with the nucleotide analogues a,b-methylene ADP (AOPCP) and adenylimido-diphosphate (AIP) and with 2'-adenosine monophosphate (2'-AMP). While the depression elicited by 5'-nucleotides was completely antagonized by the action of adenosine deaminase, AOPCP and 2'-AMP were only partially antagonized. The findings indicate that nucleotides on their own are capable of modulating synaptic transmission but that the physiologically more prevalent 5'-AMP is mediating its effect via adenosine. By producing this membrane permeable compound and allowing its re-uptake, the 5'-nucleotidase may determine the time course of purinergic action.

In the PC12 clonal nerve cell line derived from a rat pheochromocytoma, the activity of acetylcholinesterase (AChE) is regulated by nerve growth factor (NGF). The specific activity of AChE was significantly increased 2 days after exposure of PC12 cells to NGF (8 X 10(-8) M), and reached its maximal increase of 94% after 3 days. Thereafter the specific activity of AChE did not significantly vary during the following 7 days. AChE cytochemistry showed the enzyme activity to be localized predominantly in cisternae of the rough endoplasmic reticulum, with a strongly enhanced activity after NGF treatment.