Protein kinase C, an enzyme that is activated by the receptor-mediated hydrolysis of inositol phospholipids, relays information in the form of a variety of extracellular signals across the membrane to regulate many Ca2+-dependent processes. At an early phase of cellular responses, the enzyme appears to have a dual effect, providing positive forward as well as negative feedback controls over various steps of its own and other signaling pathways, such as the receptors that are coupled to inositol phospholipid hydrolysis and those of some growth factors. In biological systems, a positive signal is frequently followed by immediate negative feedback regulation. Such a novel role of this protein kinase system seems to give a logical basis for clarifying the biochemical mechanism of signal transduction, and to add a new dimension essential to our understanding of cell-to-cell communication.

https://science.sciencemag.org/content/sci/233/4761/305.full.pdf

Studies and perspectives of protein kinase C

A combination of field and laboratory investigations has revealed that the temporal patterns of testosterone (T) levels in blood can vary markedly among populations and individuals, and even within individuals from one year to the next. Although T is known to regulate reproductive behavior (both sexual and aggressive) and thus could be expected to correlate with mating systems, it is clear that the absolute levels of T in blood are not always indicative of reproductive state. Rather, the pattern and amplitude of change in T levels are far more useful in making predictions about the hormonal basis of mating systems and breeding strategies. In these contexts we present a model that compares the amplitude of change in T level with the degree of parental care shown by individual males. On the basis of data collected from male birds breeding in natural or captive conditions, polygynous males appear less responsive to social environmental cues than are monogamous males. This model indicates that there may be wi...

The "Challenge Hypothesis": Theoretical Implications for Patterns of Testosterone Secretion, Mating Systems, and Breeding Strategies

The efferent projections of the suprachiasmatic nucleus (SCh) in the rat hypothalamus have been reexamined with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L), which displays labeled axons with the clarity of a Golgi impregnation. Fibers from the SCh can be divided into six pathways for descriptive purposes. By far the densest terminal field arising from cells in the SCh ends in a roughly comma-shaped zone between the SCh and paraventricular nucleus on the one hand and the periventricular nucleus and anterior hypothalamic area on the other. A few axons continue dorsally from this "subparaventricular zone" to pass through parvicellular parts of the paraventricular nucleus and the overlying midline thalamic nuclei to end in midrostrocaudal parts of the paraventricular nucleus of the thalamus, and a larger number continue caudally to end in the dorsomedial nucleus, dorsal parts of the cell-sparse zone surrounding the ventromedial nucleus, and the posterior hypothalamic area. The other five pathways all consist of relatively small numbers of fibers and give rise to relatively sparse terminal fields. The second pathway consists of rostrally directed fibers that end in ventral parts of the medial preoptic area and anteroventral periventricular nucleus. The third consists of anterodorsally oriented fibers that pass through the medial preoptic nucleus and adjacent regions to end ventrally in the intermediate lateral septal nucleus. The fourth consists of fibers just caudal to the third group that end in the preoptic continuation of the bed nucleus of the stria terminalis, as well as in the parataenial nucleus and rostral part of the paraventricular nucleus of the thalamus. The fifth consists of laterally directed fibers that course over the optic tract to end in the ventral lateral geniculate nucleus. And the sixth consists of fibers that course posteriorally through the anterior hypothalamic and retrochiasmatic areas to end in the cell-sparse zone between the arcuate nucleus and ventral parts of the ventromedial nucleus, as well as in adjacent parts of the lateral hypothalamic area. The distribution of projections labeled following PHA-L injections centered in the subparaventricular zone was also examined and was confirmed with retrograde tracer experiments (Watts and Swanson: J. Comp. Neurol. 258:230-252, '87). The results indicate that the subparaventricular zone projects to essentially the same regions as the SCh, only much more densely, and also sends fibers back to the SCh.(ABSTRACT TRUNCATED AT 400 WORDS)

Efferent projections of the suprachiasmatic nucleus: I. Studies using anterograde transport of Phaseolus vulgaris leucoagglutinin in the rat

Introduction * Hormonal and Nonhormonal Basis of Maternal Behavior * Experiential Factors Influencing Maternal Behavior * Motivational Models of the Onset and Maintenance of Maternal Behavior and Maternal Agression * Neuroanatomy of Maternal Behavior * Neurochemistry and Molecular Biology of Maternal Behavior * Paternal Behavior * Neural Basis of Parental Behavior Revisited * Human Implications

The Neurobiology of Parental Behavior

A large number of hormones, neurotransmitters and other signal substances utilize adenosine 3',5' cyclic monophosphate (cAMP) as an intracellular second messenger. Cyclic AMP regulates a number of different cellular processes such as cell growth and differentiation, ion channel conductivity, synaptic release of neurotransmitters, and gene transcription. The principle intracellular target for cAMP in mammalian cells is the cAMP-dependent protein kinase (PKA). The fact that this broad specificity protein kinase mediates a number of discrete physiological responses following cAMP-engagement, has raised the question of how specificity is maintained in the cAMP/PKA system. Here we will describe features of this signaling pathway that may contribute to explain how differential effects of cAMP may be contributed to features of the PKA signaling pathway.

https://www.bioscience.org/1997/v2/d/skalhegg/skalhegg.pdf

Specificity in the cAMP/PKA signaling pathway. differential expression, regulation, and subcellular localization of subunits of PKA.

Serum concentrations of testosterone plus dihydrotestosterone (T-DHT), 5α-androstane- 3α, 17β-diol (Diol) and androsterone were measured during sexual maturation in male rats. Diol concentrations of 1 to 2.25 ng/ml were found in animals 10–90 days of age with no significant changes. Diol was the major androgen (5.75-8 times T-DHT) from age 20–40 days. Androsterone rose to 1.25 ng/ml at 25 days of age and declined to values of <0.5 ng/ml from age 30–90 days. Testosterone-DHT levels were 1 ng/ml or less from 10–40 days of age, and then rose to a peak at 60 days. The ratio of Diol to T-DHT was significantly elevated from age 20–35 days, indicating that Diol is the major androgen in circulation at this time. Acute treatment of 33 day old rats with LH, but not with FSH, resulted in a dose-dependent increase in serum T-DHT, Diol, and androsterone. The dose-response and time course of response for the three steroids were nearly identical. Changes in testes capacity to secrete androgens were assessed at 25, 33, 4...

Serum 5alpha-androstane-3alpha,17beta-diol, androsterone, and testosterone concentrations in the male rat. Influence of age and gonadotropin stimulation.

This case study provides objective evidence supporting the hypothesis that female ejaculation, a partial, infertile homologue of male ejaculation, exists. A karyotypically normal, multiparous woman suffered for a decade with urinary stress incontinence. During that time she had learned to inhibit an orgastic response which led to bedwetting. Although the liquid produced did not appear to be urine, she falsely concluded that her orgasmic expulsion was a manifestation of urinary incontinence. Using feedback from a Vaginal Myograph, she learned to do Kegel exercises properly, and the urinary stress incontinence soon disappeared. Around this time she became aware of the concept of female ejaculation and its possible association with an erotically sensitive area that could be stimulated through her anterior vaginal wall. Stimulation of this area, the “Grafenberg spot,” produced what she described as orgasm which felt “deeper” than orgasms in response to vulvar stimulation. Such an orgasm was often acc...

Female ejaculation: A case study

Hormonal responses of male gerbils to stimuli from their mate and pups.

A radioligand binding technique was used to study beta-adrenergic binding sites on rodent Leydig cells. Beta-Adrenergic binding sites were found on Leydig cells in both the rat and mouse. Binding of [3H]CGP-12177 [4-(3-t-butylamino-2-hydroxypropoxy)-[5,7-3H]benzimidazole-2-one] to purified rat Leydig cells was found to be saturable, temperature and time dependent, stereospecific, and readily reversible by the beta-adrenergic antagonist propranolol. Scatchard analysis revealed the presence of high-affinity sites with an apparent dissociation constant (Kd) of 0.79 +/- 0.22 nM and maximal binding capacity (Bmax) of 1716 +/- 245 sites per rat Leydig cell. Competition of various beta-adrenergic agonists and antagonists with [3H]CGP indicates an order of potency of L-isoproterenol greater than epinephrine = salbutamol greater than norepinephrine greater than D-isoproterenol and dl-propranolol = ICI 118,551 much greater than atenolol, respectively. These observations suggest that the binding sites are predominantly of the beta 2-receptor subtype. Incubation of freshly isolated rat Leydig cells with luteinizing hormone (100 ng/ml) caused consistent stimulation of androgen production, but only occasional stimulation by the beta-agonist isoproterenol (10 microM) was observed. However, these cells consistently responded to the beta-agonist after 3 h in primary cultures. These findings indicate that rodent Leydig cells possess beta-adrenergic binding sites and point out a possible dissociation between receptor recognition and physiologic response.

/pdf/characterization-of-beta-adrenergic-binding-sites-on-rodent-3s99y02wn7.pdf

William H. Moger

Papers

Serum 5alpha-androstane-3alpha,17beta-diol, androsterone, and testosterone concentrations in the male rat. Influence of age and gonadotropin stimulation.

Female ejaculation: A case study

Hormonal responses of male gerbils to stimuli from their mate and pups.

Characterization of beta-adrenergic binding sites on rodent Leydig cells.

Plasma androgen levels during male parental care in a tropical frog (Eleutherodactylus).