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Blood platelets and brain membranes of SIV and Lewis rats both exhibited two saturable binding sites for 5-hydroxytryptamine (5-HT) in the concentration range 1-100 nM. The Kd values for the high-affinity sites were 4-6 nM and for the low-affinity sites 20-40 nM in both tissues of both rat strains. Blood platelets had 100-200 times more binding sites per mg protein (Bmax) than brain membranes. Thus, 5-HT receptors of platelets may be used as models for those of cerebral 5-HT-neurons.

Rat cerebral cortex slices were incubated with 1muM [3H]4-aminobutyrate or [3H]L-glutamine. The subcellular distribution of the accumulated labelled substances were determined by fractionating the nuclei-free homogenates on a 5-step discontinuous sucrose density gradient in a B XIV zonal rotor. The gradient was designed to separate the synaptosomes into 3 subpopulations of increasing density. The patterns of distribution of [3H]4-aminobutyrate and [3H-a1L-glutamate in the three synaptosomal peaks were distinctly different. This indicates the presence of separate types of nerve ending accumulating these two potential neurotransmitters, which are known to be metabolically closely linked through the enzyme glutamate decarboxylase. Recentrifugation of the 3 synaptosomal peaks on flat step gradients in a swingout rotor did not result in any further enrichment in transmitter-specific synaptosomes.

Diurnal cycles for 8 ligand receptor pairs and choline acetyltransferase (ChAT) activity in 3 brain regions differed markedly in two rat lines, both of Wistar origin. Statistically significant differences between diurnal cycles in the two rat lines were found in the following parameters: 24 h means in 6 of 11 measurements, magnitude of cycle amplitudes, and phase position in 6 of 11 measurements, up to complete reversal of the acrophases in the case of ChAT activity in hippocampus. The importance of these findings--such major differences in two closely related rat lines--is obvious in any attempt to compare receptor-binding studies per se between laboratories using the same strain but not line, in studies of receptor rhythm characteristics, and in particular, for analysing the effects of brain-reactive drugs. While there are some reports on strain-dependency of cyclic functions, we are not aware that line-dependency has previously been described.

Serum from patients with multiple sclerosis (MS) and other diseases was added to the medium perfusing isolated hemisected frog spinal cord, and the effect on ventral root responses (VRR) tested. As control, a standardized commercial human serum (Moni-trol I) was used. In 25 out of 40 spinal cord preparations Moni-trol gave inhibition of VRR ranging from 2.8 to 23.1%. 76% of the tests with confirmed MS sera showed inhibition of VRR, after deduction of the control serum effect, while 53% of the tests with sera from other diseases were inhibitory. Sera from cases of suspected but clinically unconfirmed MS gave strong inhibition (above 20%).

Binding in 14 ligand membrane receptor pairs and choline acetyltransferase activity were studied at 4-hour intervals during a 24-hour cycle (12:12 light:dark). Cortex, hippocampus, cerebellum, striatum and brainstem were prepared from 3-, 12- and 24-month-old male rats. Cholinergic, alpha- and beta-adrenergic, dopaminergic, serotonergic, gabaergic and opiate binding were determined. In the aged animals, the times of the binding maxima are no longer locked to the same time of the light:dark cycle, and the cycle phases themselves are shifted in comparison to those of the young and adult group. Cycle amplitudes were smallest in the 12-month-old rats, increasing significantly in the 24-month group. The age changes in the overall (24-hour) means fall into 4 different patterns, none of which shows a linear age-related decrease. This points out the great importance of including an adult group (12 months) in all ageing studies on small mammals.

In a personal statement the author takes the view that gerontology and geriatrics deal with the same fundamental biological phenomenon, namely loss of adaptability and of the capacity to maintain the parameters of homeostasis. Two focal points of recent research in gerontology are cell cultures and the central nervous system. Work with cell cultures has so far been unexpectedly disappointing as far as basic understanding of the ageing process in vivo is concerned. Biochemical, morphological, physiological and pharmacological investigations into the ageing brain have on the other hand provided a wealth of new data which promise major insights into basic mechanisms of the ageing process. Aim of all gerontologocal research must be an "old age worth living" rather than a speculative search for a prolongation of lifespan.

The uptake of [3H]glycine and [3H]L-glutamate into slices of the dorsal and ventral halves of rat spinal cord taken from the thoracal (T3-9) and lumbar (L1-6) regions was determined in the concentration range 2 - 1 000muM. For both amino acids and in all four tissue pieces (thoracal dorsal and ventral, lumbar dorsal and ventral) biphasic linear regressions were obtained from the Lineweaver-Burk plots, demonstrating saturable transport mechanisms both in the high-affinity and in the low-affinity range. No significant dorsal-ventral or lumbar-thoracal differences were found for the transport constants Km of both amino acids. For the maximum velocity V similar dorsal-ventral and lumbar-thoracal gradients were found for both glycine and L-glutamate. These results, which are not entirely in agreement with the distribution of the endogenous pools of these amino acids, are critically discussed in view of the proposed function of high affinity uptake at the synapse.