The coexistence of gamma-aminobutyric acid (GABA), glutamate decarboxylase (GAD), and cholecystokinin (CCK)- or somatostatin-immunoreactive material in the same neurons was studied in the hippocampus and visual cortex of the cat. One-micrometer-thick serial sections of the same neuron were reacted to reveal different antigens by the unlabeled antibody enzyme method. All CCK- and somatostatin-immunoreactive neurons in the cortex and all CCK-immunoreactive and the majority of somatostatin-immunoreactive neurons in the hippocampus that could be examined in serial sections were also immunoreactive for GABA. In neurons that were immunoreactive for GAD it was often possible to demonstrate immunoreactivity for one of the peptides as well as for GABA. GABA-immunoreactive neurons, as revealed by an antiserum to GABA, were present in all layers of the cortex and hippocampus, and their shape, size, and distribution were similar to GAD-immunoreactive neurons. All GAD-immunoreactive neurons were also positive for GABA, but the latter staining revealed additional neurons. CCK/GABA- and somatostatin/GABA-immunoreactive neurons were present mainly in layers II and upper III and in layers V and VI in the visual cortex. CCK/GABA-immunoreactive neurons were most frequently present in the strata oriens, pyramidale, and moleculare of the hippocampus and in the polymorph cell layer of the dentate gyrus. Somatostatin/GABA-immunoreactive neurons were localized mainly in the stratum oriens and in the hilus of the fascia dentata. The two peptides could not be found in the same neuron. The majority of neurons that were GABA immunoreactive did not stain for either peptide. The presence of CCK- and somatostatin-immunoreactive material in GABAergic cortical neurons raises the possibility that neuroactive peptides affect GABAergic neurotransmission.

The relationship between a rat's locomotor response to a novel environment and its behavioral and dopaminergic responses to cocaine was examined. Subjects were divided into two groups based on their locomotor response to a novel environment. Subjects who had a novelty response above the median were classified as high responders (HR), while those with a novelty response below the median were classified as low responders (LR). Following administration of cocaine-HCl (0, 2.5, 5.0, 10.0, or 15.0 mg/kg), HR rats showed a greater locomotor response than LR rats. Moreover, there was a significant correlation between a subject's locomotor response to the novel environment and the locomotor response to either 10.0 (r = 0.65) or 15.0 (r = 0.92) mg/kg cocaine. In a separate experiment, the extracellular concentration of dopamine in the nucleus accumbens (NACC) was monitored using microdialysis procedures. Following cocaine administration (15.0 mg/kg) HR rats showed a larger NACC dopamine response and greater locomotor activity than LR rats. In addition, there was a threefold greater locomotor activity to dopamine ratio in HR rats than in LR rats. A correlation between a subject's locomotor response to a novel environment and the dopaminergic response to cocaine was also evident. These results suggest that differences in the locomotor response to cocaine can, to some degree, be predicted by a rat's locomotor response to a novel environment, and that variations in dopamine-dependent mechanisms of the NACC may underlie these individual differences.

Golgi-impregnated and gold-toned preparations of cat hippocampus were studied under the light and electron microscope in order to characterize synapses in contact with the axon initial segments of pyramidal neurons. The initial segment of the axon emits spine-like appendages and it was sometimes seen to be in apparent contact with thin varicose fibers that climbed along it. The latter type of varicose axon terminal segments occurred at the base of pyramidal neurons in all regions of the hippocampus and in the subiculum: they are 20 to 40 w long, contain 3 to 15 varicose swellings, and are interconnected by thin horizontal or arcadic fibers. It was established by electron microscopy of gold-toned material that light microscopically identified varicosities of these terminal segments were in symmetrical synaptic contact exclusively with axon initial segments; four of the initial segments in the CA1 region could be traced back to pyramidal neurons. Thus the pyramidal cell of the cat hippocampus receives input along its axon initial segment from boutons that probably originate from axoaxonic cells of the type found previously in the cerebral cortex and monkey hippocampus.Antiserum to glutamate decarboxylase was used to study the distribution and nature of cells and processes that bound the antiserum. Several different types of immunoreactive cell bodies were found in all layers in regions CA1 to CA3, suggesting that many kinds of GABAergic interneurons are present in the hippocampus. Fibers and varicosities that were immunoreactive for glutamate decarboxylase were also found in all layers. The most conspicuous patterns formed by immunoreactive varicosities were in the pyramidal cell layer, where they occurred as pericellular nets around all pyramidal neurons. Immunoreactive processes or varicosities also followed both apical and basal dendrites, but a very high density of immunoreactive varicosities was seen around fine (diameter 2 to 4 pm) tube-like structures that could sometimes be seen to lie at the base of pyramidal neurons. Electron microscopic analysis of immunoreactive structures that had first been identified in the light microscope established that the varicosities outlining such tube-like structures were boutons in symmetrical synaptic contact with the axon initial segments of pyramidal neurons; the other immunoreactive varicosities were boutons in symmetrical contact with cell bodies and apical and basal dendrites of pyramidal neurons. Detailed study of 19 axon initial segments showed that immunoreactive boutons occur most commonly along more distal parts of the initial segment, where they almost completely surround the axon and form symmetrical synapses not only along the main axon, but also with its spines. Since the glutamate decarboxylase-immunoreactive boutons comprised 92% of all symmetrical synaptic boutons along the initial segments, it was concluded that the axoaxonic cell uses y-aminobutyrate as its transmitter.It is suggested that the pyramidal neuron receives input from more than one t...

Crohn's disease is often complicated by anaemia. Assessment of iron deficiency may be hampered by modification of the serum ferritin concentration because of the associated acute phase response when disease is active. However a ferritin value of < 5 micrograms/L is indicative of iron deficiency, which is rarely found in Crohns disease.